Mobi by Taalib Minhas

Mobi. Power assissted trolley TAALIB MINHAS DM3306: Major Project April 2014 First supervisor: Dr Faraz Nickpour Second supervisor: Dr Fabrizio Ceschin

Contents

1.0

Introduction

1.1 Who uses portable oxygen?

5.1 Initial concept directions

1.2 Empathy study

5.2 Weighted Factor scoring

1.3 What is COPD?

5.3 Market size

1.4 The need for portable oxygen

5.4 Use case storyboarding

2.0 Research

5.5 System boundaries

2.1 Types of portable oxygen

5.6 Anthropometrics

2.2 User journey 2.3 Expert interviews 2.4 User observations 2.5 User interviews 2.6 A day with Yolande

3.0 Synthesis 3.1 Key insights

5.0 Industrial Design

5.7 Use case storyboarding

6.0 Electronics 6.1 Component selection 6.2 Circuit design V1 6.3 Test rig V1 6.4 Circuit design V2 6.5 Test rig V2

3.2 Initial concept directions

6.6 Piezo sensor

3.3 Expert / user feedback

6.7 Force sensor

3.4 SWOT / weighted factor scoring

6.8 Final Electronics

3.5 Target market

6.9 Electronics implications on design

4.0 Specification 4.1 Customer needs specificaion 4.2 Product Design specification

7.0

Develop 7.1 Learning from others

7.3 Weighted Factor scoring

5.3 Designing the clutch

7.4 Detail design

5.4 The charging dock

7.5 Aesthetic

5.5 Mechanisms

7.6 Feedback

5.6 IP65

7.7 Modular product architecture

5.7 Tolerance analysis

8.0 Final Design 8.2 Aesthetic 8.3 Materials

9.0 Design for Manufacture 9.1 Optimising parts 9.2 Costing - Manufactured components 9.2 Costing - Sourced components

5.1 The Oxygen bag 5.2 Testing the market

8.1 Branding

11.0 Further Development

7.2 Design directions

7.8 Design review

10.0 Review 10.1 Reviewing PDS requirements

Abstract This report details the design development of Mobi. A power assisted trolley that makes carrying loads easier for people with all kinds of disabilities from Chronic fatigue to COPD. The projects initial focus wasnâ&#x20AC;&#x2122;t so broad and stemmed from a single fact. Adherence to portable oxygen therapy is just 22%.

1.0 INTRODUCTION

1.1 Who uses portable oxygen? An estimated 89% of users of portable oxygen have COPD (Stoller, 2010), a disease which is predicted to be the worldâ&#x20AC;&#x2122;s third biggest killer by 2020 (WHO, 2013). Oxygen therapy has been proven to prolong patient life in COPD by an estimated 5 years (Croxton, Bailey, 2006). Then why do only 22% of those prescribed portable oxygen actually use it? Studies have proven that adherence to oxygen has many barriers, the biggest of which include; the physical difficulty of adopting oxygen and the sense of social stigma related to using the equipment in public (Earnest, 2002). The following research explores the issues faced by oxygen users and how the equipment used can be designed to address those issues. 1.2 Empathy study The first thing I did was put on a cannula and spend a day wearing what appears to look like oxygen equipment. I wore a hidden camera to look back over how many people were staring at me. I was well aware whilst wearing the equipment that if I looked at people they would immediately look away. So by filming it I was able to get a true reflection of how much more attention you actually get.

1 Stoller, J. Panos, R., Krachman, S., Doherty, D., Make, B. (2010).Oxygen therapy for patients with COPD. 1 (1), 179 - 187.

2 WHO. (2013). Chronic obstructive pulmonary disease (COPD). Available: http://www.who.int/mediacentre/factsheets/ fs315/en/. Last accessed 30th Sep 2013.

3 Thomas L. Croxton , William C. Bailey. (2006). Long-term Oxygen Treatment in Chronic Obstructive Pulmonary Disease: Recommendations for Future Research. Available: http://www.nhlbi.nih.gov/ meetings/workshops/lott-wksp.htm. Last accessed 11th October 2013.

4 Dr. Mark A. Earnest MD, PhD. (2002). Explaining adherence to supplemental oxygen therapy. Journal of General Internal Medicine. 17 (1), 749 - 755.

I was shocked by the social rumifications of using oxygen in public. On the bus people avoid sitting next to you, walking through a shopping mall you get groups of people watching ...

Design Process When starting this project I outlined my process in terms of the double diamond. I was very aware that I was starting a project with no idea of a product solution and so I began with that aim clearly in mind and constructed the diagram below. This really helped me to stay on track and keep a clear vision of where I needed to be heading. It also gave me a good starting point to construct a project plan.

Discover

Develop

Deliver Design for Manufacture

User research

Development of the design brief

Product architecture

Expert research

Mapping out the users needs.

Industrial design

Final CAD

Market research

Concept development and PDS

Ergonomics / anthropometrics

Final prototypes / models

Product system research

Concept weighted scoring.

User testing / Feedback

Product Financial model

Possible collaboration?

Concept matrix.

Iterative design

5 Design council. (2007). Introducing design methods. Available: https://www. designcouncil.org.uk/news-opinion/ introducing-design-methods. Last accessed 09th September 2013.

Project plan At this stage a project plan was made using Microsoft Project. This actually was very helpful in making sure that the deadlines along the year were met on time and with enough preperation.

1.3 What is COPD? Chronic Obstructive Pulmonary Disease (COPD) is a respiratory illness that is a combination of chronic bronchitis and emphysema. Ultimately it causes reduced airflow in the lungs and extreme breathlessness. Inflammation of the bronchial tubes causes excess production of mucus which clogs the airways and can harbor bacteria leading to infections. Meanwhile the alveoli shrink and oxygen absorption into the blood reduces. Oxygen deprivation leads to chronic hypoxia (lack of oxygen) in the organs. This causes the onset of many other problems most prevalent of which is pulmonary hypertension. Low oxygen concentrations cause changes to the pulmonary arteries over time putting strain on the heart’s right ventricle and eventually leading to heart failure (Libby, P., 2007). Low oxygen levels also lead to cognitive impairment, with studies suggesting that the level of decline in cognitive function would likely be associated with a 22% increase in the average number of difficulties experienced in performing daily tasks. (Hung, 2009) 1.4 The need for portable oxygen Quality of life is severely affected in patients with COPD, with 80% of patients being hospitalized following an exacerbation with a health status rated by physicians as being ‘Worse than death’. Studies prove that the single most important factor associated with good quality of life in COPD was level of physical activity. Patients who lived the most sedentary lifestyle had the lowest quality of life. (Primary care research unit, 2011) Portable Oxygen enables patients to regain their mobility and is related to significant improvements in health related quality of life. One study involving 41 patients tested the distance they were able to walk in 6 minutes with oxygen and with a placebo. Each patient was on average able to walk 40m more with oxygen whilst keeping blood oxygen concentrations ≤ 92% (baseline safe level). (Dept. of respiratory services, 2002).

6 Libby, P. Braunwald’s Heart Disease 8th Edition, W.B. Saunders, 2007.

7 Hung, W. American Journal of Respiratory and Critical Care Medicine, July 15, 2009; vol 180: pp 134-137.

8 Arne M, Lundin F, Boman G, Janson C, Janson S, Emtner M.. (2011). Factors associated with good self-rated health and quality of life in subjects with self-reported COPD.. Primary Care Research Unit, County Council of Värmland. 10 (1), 511 - 519.

9 T. Eaton, J.E. Garrett, P. Young, W. Fergusson, J. Kolbe, S. Rudkin, K. Whyte. (2002). Ambulatory oxygen improves quality of life of COPD patients: a randomized controlled study. European Respiratory Journal. 1 (1), 306 - 312.

2.0 RESEARCH

2.1 Types of portable oxygen The most widely used type of oxygen is the traditional aluminum cylinder, comprising of an estimated 70% of the market (Benjamin D, 2013). This is the cheapest of all types even when taking service cost into account. Cost is a particularly important factor for this relatively expensive treatment, as global statistics show that 90% of COPD deaths occur in low and middle income areas (WHO, 2013). Oxygen cylinders are usually the first type of oxygen a new patient will be prescribed, and adherence is predicted to be lowest in the first few months of use (Earnest, 2002). Liquid oxygen is the most expensive form of treatment. It also requires the fitting of a liquid oxygen storage unit in a patient’s house, which uses electricity to keep the liquid oxygen at -180°c. It does however come with the benefit of being able to store the same amount of oxygen as a cylinder within an overall lighter package. This type of oxygen is usually only prescribed to patients with the worst disease progression, due to the high cost. Portable concentrators use the surrounding air. Which comprises of ≈ 79% nitrogen, ≈ 20% Oxygen and ≈ 1% other gases (Mackenzie, 1995) and pull this air through a filter that extracts most of the nitrogen, leaving ≈ 95% pure oxygen. However, they are currently limited by technology such as capacity and weight of lithium ion batteries. However, when this technology progresses to the point where a concentrator can weigh 2kg and provide a continuous flow rate for up to 6 hours, it will become much more popular. At the moment it is too expensive for light users, cannot provide enough flow rate for heavy users and is just too heavy for everyone, although more aesthetically pleasing and requiring no deliveries.

10 Benjamin Dillon, Phone interview. Air Liquide, 06 Oct 2013

11 Dr. Mark A. Earnest MD, PhD. (2002). Explaining adherence to supplemental oxygen therapy. Journal of General Internal Medicine. 17 (1), 749 - 755.

12 Mackenzie, F.T. and J.A. Mackenzie (1995) Our changing planet. Prentice-Hall, Upper Saddle River,NJ,p288-307. (After Warneck, 1988; Anderson, 1989; Wayne, 1991.)

Cylinders

Liquid

Concentrators

New cylinders are delivered on a daily / weekly basis. This is the most popular type of oxygen.

A home Liquid oxygen storage unit is also needed. This unit must be refilled on a weekly basis. The portable unit is then refilled from this home unit.

The benefit of a concentrator is not requiring any deliveries. It just requires recharging after use and the changing of filters on a regular basis.

2.2 User journey The process of being prescribed oxygen in the first place usually starts with a visit to the GP. Youâ&#x20AC;&#x2122;ve started noticing your feeling more out of breath doing daily activities than usual.

13 WHO. (2013). Chronic obstructive pulmonary disease (COPD). Available: http://www.who.int/mediacentre/factsheets/ fs315/en/. Last accessed 30th Sep 2013.

64 million people in the world are diagnosed with COPD 3 million of which are in the UK.

Visit to the GP

Pulmonary doctor

Here the patients condition is assessed and they are asked to visit a hospital where a full spiromitory and oximitary examination can be done.

The Doctor assesses the results of the tests and decides if the patient needs to be using ambulatory oxygen.

Pulmonary nurse The nurse conducts a spiromitory and blood oxgen exam.

Physiotherapist A Physiotherapist puts the patient through a few tests to see if they are compatible with Oxygen. These tests are usually to BTS or NICE guidelines.

Pulmonary nurse

Technician

Use

Here the patients results from the test are monitored and along with a questionnare asking the patients requirements such as â&#x20AC;&#x2DC;How active are you?â&#x20AC;&#x2122; they choose which type of Oxygen they can give the patient.

This is usually the delivery man who sets up the Oxygen system in a patients home. Research indicates that patients get most advice about Oxygen use off this person.

The patient has to go on using the Oxygen they have been prescribed and overcome any of the issues related to using it themselves.

Patients are also warned of the dangers of smoking with Oxygen and asked if they do smoke.

2.3 Expert interviews Through contact with Hillingdon hospital I was able to meet Dr Ann Nolan. An oxygen specialist for the last 20 years, Ann was able to give me insights into the problems faced by patients, doctors and regulatory issues to do with Oxygen prescription. She also put me into contact with Dr Samantha Kon. A pulmonary research doctor whoâ&#x20AC;&#x2122;s medical publications I had been reading to gain a greater understanding of the problems faced by COPD patients. My next visit was to Harefield hospital. The largest respiratory clinic in europe. They were running pulmonary rehabilitation clinics during my visit and I was able to meet a few nurses and had the opportunity to interview Denise Williams. A Physiotherapist who, for the last 10 years, has been working with patients who have COPD to try and help them exceed their current state of mobility.

Research Inisights Patients smoking This is a big problem with portable oxygen. Most cases of COPD are caused by pack years of smoking. Some patients find it hard to kick the habit and the result when carrying contained oxygen has resulted in many 16 deaths in the UK over the last 3 years. Heavy equipment According to Dr Ann Nolan 60% of patients she sees prescribed oxygen are unable to carry it. In many cases these are the patients that need it the most. Social stigma Denise spends a long time with patients and builds a relationship with them. In her opinion the biggest reason younger female patients donâ&#x20AC;&#x2122;t use oxygen is because of the social rumifications.

Dr Samantha Kon PULMONARY RESEARCH DOCTOR “99% of new patients are prescribed oxygen cylinders.” Research shows that adherence is lowest in the first 6 months post prescription.

Dr Ann Nolan

Denise Williams

OXYGEN SPECIALIST

PHYSIOTHERAPIST

“Most patients find the equipment too heavy to carry around with them.”

“The social stigma stops alot of female patients from using the equipment.”

2.4 User observations The first experience observing a patient was at Harefield observing oxygen assessments. One of the patients stood out immediately. A lady in her early 60’s. She was using a portable concentrator, but during her 6 minute walk (part of assessment) her blood oxygen levels fell to 89%. The conclusion to the assessment was that due to disease progression she needed a higher flow rate of oxygen at a continuous level. This meant that she would now have to use a cylinder. On receiving this news the patient was brought to tears and when asked why the idea of using a cylinder made her feel this way her answer was:

‘It’s uncomfortable to carry’ and ‘It makes me feel like an invalid’. Some of the insights brought about by observing other patients are in the table below:

Gender

Female

Male

Age

Insights

≈ 60

Mobility: During 6 minute walk the patient was trying to take breaks by resting on the cylinder trolley which wasn’t stable enough. Psycho/social: Patient kept her oxygen in a ‘more fashionable’ looking shopping trolley she was using, which she said made her feel more dignity.

≈ 50

Mobility: Patient was pushing trolley in front as opposed to behind like it is designed for Conserving device: Pulse flow modulator makes a very audible sound, this could be an issue in more quiet public places such as libraries.

2.5 User interviews Through contact with the British Lung Foundation, the meeting of 6 patients using a variety of oxygen types was arranged. During a pulmonary rehabilitation class a semi structured interview was conducted with each of the patients on a one on one basis. A set of questions and ‘conversation starters’ were laid out prior to the event. These all revolved around the topics of; Stigma, Mobility, Comfort, General use. But at this stage it was key to keep the topics and questions broad to get a true representation of the problems patients face. All negative connotations of oxygen were avoided and instead approached from the perspective of ‘How do you think this could be improved?’ Male patients found it difficult to open up about problems they were facing. It took more in depth questions and actually asking them to use different aspects of the equipment whilst the interview was underway. This brought problems to the surface. Below I look into the insights found through two of these interviews:

Running out

Excess cable

Pulse regulator

Patients find it hard to decipher the oxygen valve into a tangible number like amount of time left.

Cannula cable can be up to 3m in length. Most patients carry this excess. One patient wrapped it around her bag.

There is no way of actually mounting the pulse regulator device that is used with oxygen cylinders.

SPENDING A DAY WITH AN OXYGEN USER

2.6 A day with Yolande Yolande was one of the patients met through the British Lung Foundation. In support of the project, she kindly agreed to be observed for the day. The journey can be seen below. At each step highlighted the mobility and psycho/social effects of using oxygen were evident. Yolande was so exhausted by the end of this journey she found it difficult to talk without getting more exasperated and out of breath.

Leave house / down stairs

Walking to bus stop

Waiting at bus stop

Getting on bus

Sitting on bus

Getting off bus

Walking in shopping mall

Trolley in supermarket

Insights from user journey As a result of this research how someone interacts with the existing carrying solution and the problems faced on a daily basis, became evident. This then allowed for the narrowing down of design focus and it provided a basis for product evaluation. The results from this and previous human centered design research helped structure a customer needs analysis. A basic product architecture was broken down and each component was analyzed from a customer needs perspective. From this information target specifications that helped understand how the user needs could be quantified were made. The PDS grew from this, as did possible concept directions.

Carrying bags

Going home

3.0 SYNTHESIS

3.1 Key insights On reflection of the research the main problems became evident. The two biggest issues summarized below: Mobility – Insights This was one of the biggest issue that patients face. The trend with stigma was that users eventually got over it. The problems with mobility on the other hand just continue to get worse with disease progression. Specific issues were highlighted; going up or down stairs, straps growing uncomfortable, straps slipping, and mounting sidewalks. One coping mechanism for this was a user made her husband carry the oxygen for her, and she walked closely enough for the cannula to reach. Psycho / Social – Insights Female users were more open about the issue of stigma. Highlighting that it was particularly a problem in the first few months of being prescribed portable oxygen. Being in a group of oxygen users made them feel less stigmatized. Male users were less open about being effected by stigma. When the topic was brought up the trend was that they don’t care much about what other people think. However, I am unsure if this was just because they didn’t want to come across as ‘weak’ or ‘vulnerable’ in the interview setting. Safety - Insights COPD being the result of pack years of smoking means there are many patients who continue to smoke after being prescribed oxygen. This is difficult to quantify as many patients lie about whether they do smoke or not. However, over the last 3 years there has been many deaths as a result of smoking whilst wearing oxygen.

3.2 Initial concept directions On the next page are the first two directions that this project was going to take. These were based off the primary and secondary research that was conducted.

CHOSEN DIRECTION Cannula

Trolley

Safety focused redesign

Mobility focused redesign

Oxygen itself is not flammable but it does support combustion. PVC, the material existing cannulas are made from, is flammable. This redesign would be focussing on designing the Cannula from a medical grade silicon and making it come in from one side only, also reducing the social impacts of wearing a cannula in public.

Cylinder type oxygen is used by an estimated 70% of patients (Richard, Air Liquide, 2013). Existing carrying solutions are not fit for purpose, awkward to use, obtrusive and have an industrial aesthetic. Redesign of a carrying solution has the opportunity to address many of the mobility and stigma related issues.

14 Richard Marsh, Telephone interview. Air Liquide, 03 Nov 13

3.3 Expert / User feedback The concept directions above were shown to the group of experts and users that I observed and interviewed, the preferred concept direction was the trolley. None of the users felt that the cannula issue was much of a problem and although the oxygen specialists recognised the problem of smoking with oxygen they felt that a product aimed at improving patient mobility through making oxygen easier to transport could be more useful. 3.4 SWOT / Weighted factor scoring A SWOT analysis and weighted factor scoring model for each concept was conducted which can be seen in my first development logbook. Through conducting this the direction that had the highest score with the least negatives was the trolley direction. Together with the user and expert feedback this reinforced the decision to focus on APPENDIX designing the trolley. Concept selection â&#x20AC;&#x201C; Scoring model Weighted scoring and model A SWOT analysis user / expert feedback was also used to narrow down concepts Criteria

Ranking / 10

Does it tick all the boxes in the mark scheme? Will I be able to implement it in 6 months? Will I learn something? Will I have a good PPP ready for Made in Brunel? Will I have a working model? Will it definitely solve a problem? (without depending on how it is implemented)

Define The brief 89% of users of portable oxygen have COPD, a disease that is predicted to be the Worldâ&#x20AC;&#x2122;s third biggest killer by 2020. Oxygen therapy has been proven to prolong patient life by around 5 years. However Adherence to Ambulatory (portable) oxygen has been measured as low as 22%. Studies suggest the most important factor associated with good quality of life was level of physical activity. Portable oxygen therapy is associated with significant improvements in health related quality of life due to the oxygen enabling patients to remain active and live a less sedentary life. The main reasons for low adherence to oxygen therapy are the physical difficulty of using oxygen and the social stigma attached to using the equipment in public. Current carrying solutions are not fit for purpose, awkward to use, obtrusive and have an industrial aesthetic. Aims The development of a more considered carrying solution for oxygen cylinders. Focusing on reducing the physical difficulty of use for prolonged periods of time and improving the aesthetic to reduce the social stigma attached to using this equipment. The project will involve in depth user research to address the day to day physical and emotional needs. Objectives The product solution should address the human centred issues that currently inhibit the users from a mobility and psycho social perspective. The product should be of high aesthetic quality and be designed to withstand 5 years of daily use. The design development should take a multifaceted approach, combining sound product engineering and refreshing yet timeless design relevant to the target user. Target market The target market was chosen based on users that had the most needs. Women. Research found that prevalence rates of COPD in the UK have peaked in men, yet they are continuing to rise in women. It is predicted that the cumulative effect of pack-years of smoking in women is the cause of this and that in the long term women will be the most effected by the disease (Rotterdam Study, 2009). This is already true in the US where more women have had COPD then men since 1998. Women with COPD describe a lower quality of life and studies show that the disease progression is much faster. This is all put down to physiological differences between men and women. Women also tend to get diagnosed with COPD at an earlier age and it is the first few months of using oxygen that adherence is lowest. Studies also show that in particular women with a lower financial income are more likely to be diagnosed with the Disease (American lung association, 2013). Taking all of this into account; my target market is women aged 45-64. 28

15 Drs. van Durme, Van Pottelberge, Joos, and Bruselle. (2009). Prevalence, Incidence, and Lifetime Risk for the Development of COPD in the Elderly. The Rotterdam Study. 135 (2), 600-684.

16 American lung association. (2013). Taking her breath away, the rise of COPD in women. Available: http://www.lung.org/ assets/documents/publications/lungdisease-data/rise-of-copd-in-women-full. pdf. Last accessed October 22nd 2013.

3.6 Existing products Sidekick / weight 3.5kg / Designed to fit all 400L cylinders The sidekick is the only product available for users to buy outside of what would be given to them through the NHS or there oxygen provider. Designed to be worn as a backpack or used as a trolley. Aesthetically this product looks more like a golf cart, which misses the target audience a product like this should be aiming for. It does have a variety of extra pockets for storage but including the weight of an oxygen cylinder the bag would weigh 6.9kg, far too much to wear as a backpack. NHS trolley / Weight: 2.5kg / designed to fit CC, DD and PD size cylinders The trolley given out on the NHS at the moment is very utilitarian. The Oxygen canister is left exposed, which allows for easy reading of the pressure gauge. The trolley also has two legs for added support whilst replacing the oxygen canister. Many of the aforementioned problems users face are as a result of having to use this product. On purchasing one of these trolleys tests were carried out to inform the product specification. The average time taken to assemble the trolley was just 36.2 seconds. However, the average time taken to secure an oxygen cylinder was 1 minute 22 seconds, due to a badly thought out securing pin.

NHS trolley

Sidekick

4.0 Specification

4.1 Customer needs specification Initially a general customer needs specification was set out based on the research conducted. These were the things I noticed that all the patients had some difficulty with and where the existing design fell short. By Satisfying these customer needs the product would directly be helping the users: Must fit the conserving device Each of the patients that used portable cyclinders with an oxygen conserving device had issues attaching it to the existing trolley. They need to keep an eye on this so it would be useful if it they could quickly access it aswell. The users coping mechanisms for this can be seen in the images.

Must fit excess cannula tubing Cannula tubing that is given to patients is usually much longer than is needed so that they have some freedom when using oxygen. However most of the time this means patients are holding excess cable in their hands. It is prone to getting caught in door handles etc...

Must be easier to replace the cylinder Due to the fact the existing trolley has a ring holding the cylinder in place and requires a threaded butt to be screwed in to secure the cylinder in place it actually is a big energy expenditure to replace the oxygen cylinder. For some of the shorter female users it can be difficult. This also takes a longer time to do than it should.

Must require less force in use The patients are already severely dibiliated from the disease. Carrying a heavy oxygen cylinder gets very tiring for most. A quick hand calcuation showed that the amount of force required in use after initial friction is overcome is 15.87N. This may not seem like much at face value but for someone disabled who needs expend this amount of force constantly for hours it can become overwhelming and is a major contributor for decreased patient mobility.

Must be more aesthetically pleasing The existing trolley has a very utilitarian design and makes it harder for patients to overcome the social stigma related to using oxygen. I found Yolande was very self conscious about how she looked before we went out I later found this was because she knows people will be looking at her and so feels the need to look her best. The design must also be more subtle. 31

4.2 PRODUCT DESIGN SPECIFICATION Explanation of terms Must

A mandatory requirement that constitutes a failed development if not met. If it is agreed that a requirement cannot be met, the requirement must be adjusted.

Want

A requirement with high importance to product success needing a high level of commitment to achieve this requirement, but failure (especially missing target by a small percentage) will not constitute a failure of the development.

Product Design Specification Prefer

A requirement with medium importance to product success, but the requirement will not be formally verified. This may be due to lack of access to relevant equipment for testing etc. Explanation of terms Must Ideal Want

COPD NHS MM Ideal N Prefer

1. 1.1 1.2 1.3 1.4 1.5 2. 2.1 2.2 3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 324.

4.1 4.2

A mandatory that or constitutes failed development if not met. A requirement with requirement low importance a guidinga nature. This may also apply to If it is agreed that a requirement cannot be met, the requirement must be adjusted. specifications that will not be able to be met in time frame of project. A requirement with high importance to product success needing a high level of commitment to requirement, but failure (especially missing target by a small percentage) will not constitute a failure of the development.

achieve this Abbreviations

Chronic obstructive pulmonary disease Sec Seconds A requirement with medium importance to product success, but the requirement will not be National health service J Joules formally verified. This may be due to lack of access to relevant equipment for testing etc. Millimetres UTS Ultimate tensile strength Newtons PAnature. Per This annum A requirement with low importance or a guiding may also apply to specifications that will not be able to be met in time frame of project.

Target market Users Primary market â&#x20AC;&#x201C; Female oxygen users with COPD aged between 45 - 64 Secondary market â&#x20AC;&#x201C; All other COPD patients with oxygen cylinders Purchaser The NHS who then prescribe the product to patients. Industrial gas supplier who oxygen is prescribed through (e.g. Air Liquide) The user, their family and friends. Functional product requirements Allow for transportation of CC, DD and PD oxygen cylinders. The product must function on all floor types. Gravel, Tarmac etc. User requirements Force required in transporting oxygen should be less than existing solution consider the use of a cannula cable consider the use of an airflow conserving device reduce average time to replace oxygen cylinder reduce average time to assemble carrying device require less energy to pull up stairs than existing solution consider other items used such as handbags that users carry consider use with public shopping trolleys Be stable enough for users to rest on when tired Be able to operate entirely with one hand Purchaser requirements Product should be collapsible for ease of storage and distribution Product should require minimal explanation for user

Must Want Want Want Prefer Height < 380mm Width > 110mm -

Must Must

15.87 N 82 sec 36.2 sec 18.32 J -

Must Must Must Want Want Want Prefer Prefer Prefer Ideal

Want Prefer

3.6 3.7 3.8 3.9 3.10

require less energy to pull up stairs than existing solution consider other items used such as handbags that users carry consider use with public shopping trolleys Be stable enough for users to rest on when tired Be able to operate entirely with one hand

4. 4.1 4.2 4.3

Purchaser requirements Product should be collapsible for ease of storage and distribution Product should require minimal explanation for user Product must adhere to medical device risk management regulations

5. 5.1 5.2 5.3 5.4 5.5 5.6

Ergonomics Height of trolley must be adjustable to maximum height Grip size of handle Anthropometric considerations be made for target market Quick for user to understand, timed product testing. Attenuation from wheels to handle kept to minimum Duo Coefficient of friction of shoulder strap high enough to avoid slipping

6. 6.1 6.2 6.3 6.4

Visual specification Aesthetic appealing to target market Aesthetic appropriate for daily use Allow for easy viewing of pressure gauge on oxygen cylinder Make the product look less threatening in public

7. Product integration 7.1 Should fit thickness of existing cannula tubing 7.2 Product should consider existing stair dimensions 7.3 Should cater for length of existing cannula tubing 7.4 Withstand temperature conditions users will be exposed to outdoors. 7.5 Withstand EPDE2013/Please paste yourtemperatures Paper No here product may be exposed to in transport / storage 7.5 Product to be kept in users home. Be non-obtrusive 13

18.32 J -

Want Prefer Prefer Prefer Ideal

ISO 14971

Want Prefer Ideal

1050 mm < 65 mm -

Must Must Must Want Prefer Prefer

Must Want Want Prefer

4.75 mm BS585 2630 mm - 5째C to 40째C -15째C to 40째C -

Must Want Prefer Prefer Prefer Ideal

8. 8.1 8.2

Service life Withstand minimum of 5 years of use (average patient time using oxygen) Product be easy to maintain

Must Prefer

9. 9.1 9.2 9.3 9.4 9.5

Material Selection Materials should be mass manufacturable Material unidirectional UTS more than maximum stress that would be applied must not release any toxins that could worsen patient respiratory impairment Materials should be non-porous for use in heavy precipitation Should be environmentally friendly / recyclable / compostable

Must Want Want Want Ideal

10. 10.1

Based on number of oxygen users in the UK, 6000 units should be manufactured PA

11. 11.1

Market Price / Manufacturing cost Target market price and manufacture cost will be based on chosen concept

Must

12. 12.1

Standards and specifications Relevant standards and specifications will be based on chosen concept.

Must

Manufacturing volume

Abbreviations COPD NHS MM

Chronic obstructive pulmonary disease National Health Service Millimetres

5.0 Industrial Design 5.1 Initial concept directions Through synthesis of my research and the selection of the trolley as the most relevant direction for this project the following four concept directions were looked into. Through cross analysis with my PDS and the requirements that were weighted as most important to least important I analysed which of these general concept directions had the possibility of becoming a useful product for the target market.

Glide Power assisted trolley A trolley that takes the load off. Using a gyroscope with tilt sensors Glide picks up when the user begins to move and an electric motor is called upon to give some mechanical advantage. From Calculating the amount of force required to pull the existing trolley, the force was found to be 15.87 Newtons. With Glide the aim would be to minimize this figure.

Duo

Buggy

Sling

Fit for any occasion

Shopping cart with bag

Handbag style carrier

This concept can be worn or used as a trolley. It uses climbing wheels or an equivalent design to give the user a mechanical advantage when going up stairs. Calculations show that with a total mass of 57.82 Newtons the existing trolley requires 18.32 Joules to be pulled up one step. Which is 293.27 Joules for a standard 16 step staircase. Duo would aim to really lower that figure.

Buggy can be used to carry more than just an oxygen cylinder. However, there is also the option of just taking the cylinder in the detachable shoulder bag. Inspiration for this design came from meeting a patient who hid the canister inside her shopping trolley. Buggy would be useful for oxygen users who already use shopping trolleys as there are none on the market that are tailored to also carry oxygen.

With the introduction of a new size of oxygen cylinder, designed to be filled up by the user at home, manufacturers have made something just about light enough to carry on the users shoulders (1.9Kg). However there are currently no carrying solutions tailored just for the new cylinder. Sling would be an aesthetically pleasing, comfortable and discreet solution for these new cylinders. It would also minimize cannula cable exposure, as the cable could be fed from behind the user.

5.2 Weighted factor scoring model The different concept directions were scored based on their ability to address the requirements of the PDS. The design that has the biggest potential in addressing this was found to be â&#x20AC;&#x2DC;Glideâ&#x20AC;&#x2122; (power assisted trolley). However there were aspects of Glide that scored very low and need to be taken into consideration thoroughly during the design process. These can be seen on the left but are that the product should be collapsible for ease of storage and distribution and that the product should require minimal explanation for the user. However for all of the aspects of the PDS that Must be met Glide scored highest with the potential to meet all of them. On this basis this design direction was taken.

5.3 Market size

How many people use portable oxygen? 17

Across the UK there are 3 companies that distribute oxygen cylinders. Air products, Air liquide and BOC. These 3 companies have their own areas around the country that they manage. Air Liquide manage all the patients in London. They were contacted to find out how many people in London are currently using portable oxygen and this was found to be roughtly 32,000 people. (Lindsay Smarthill, 2014)

Production Quantity

100,000 Modular Tooling

10,000 1,000 100 10 1

Direct Fabrication

CNC Machining

Vacuum Casting

Injection Molding

Prototype Molding

Fused Deposition Modeling

Low

Selective Laser Sintering

High Part Complexity

If I was to take the number of oxygen users in London alone as the only target market for this product manufacturing processes such as injection moulding would still be viable. It was very difficult to find out how many oxygen users there are in the UK as Air Products and BOC both did not want to disclose how many patients they had in there respective areas although I did find that there was 12,000 (Lindsay Smarthill, 2014) managed by Air Liquide in the â&#x20AC;&#x2DC;Midlandsâ&#x20AC;&#x2122; area. However the concept for a powered trolley would not be restricted for just oxygen cylinders, they could be used to carry liquid oxygen or the heavier oxygen concentrators. Taking this into account the device has the potential to help all oxygen users. In the United States alone a study done in 2011 found over 1 million recipients of medical oxygen just through a single healthcare provider (NCBI, 2011) 38

Lindsay Smarthill. 2014. Air Liquide Portable oxygen users. Interviewed by Lindsay Smarthill [radio] Mobile Phone, January 09th 2014.

18 Oxygen therapy for patients with COPD. 2014. Current Evidence and the Long-Term Oxygen Treatment Trial, 01 (138), pp. 179-187.

Who else needs a powered personal trolley? 19

35 diseases have weakness as a major symptom, 72 common diseases leave people suffering with severe fatigue. A product with the features of a personal powered trolley actually has the potential to meet the needs of a much larger target audience. People who suffer from Chronic Fatigue, Multiple Sclerosis, Cystic Fibrosis and many other common diseases have trouble carrying everything from heavy laptop bags and shopping to other medical equipment. Just like with COPD patients this places a restriction on what they can do and usually leads to living a more sedentary lifestyle. A socially acceptable carrying aid could alleviate alot of the issues that they have.

NHS uk. (2012). Chronic Fatigue Syndrome. Available: http://www.nhs.uk/conditions/ Chronic-fatigue-syndrome/Pages/ Introduction.aspx. Last accessed 13 February 2014.

20 MS society. (-). What is MS?. Available: http://www.mssociety.org.uk/what-is-ms.

Chronic Fatigue Chronic Fatigue syndrome is a severly debilitating disease that effects people at varying levels of severity. It causes persistant fatigue that can’t go away through rest or sleep. It is estimated that in the UK alone 250,000 people live with the disease (NHS, 2012). The effects of the disease on lifestyle vary with patient severity. From needing the extra day off work to finding it difficult to brush your own teeth. There is no cure for the disease but over exertion worsens symptoms, patients call this ‘Payback’. The more someone with CF excerts themselves the worse the disease can become. Multiple Sclerosis Multiple Sclerosis, like CF, is a disease of the nervous system. So much like CF disease severity ranges between small symptoms such as a numb feeling in your hand to near paralysis. There are roughyly 100,000 people in the UK with MS (MS Society, 2011). The intention of this research was for two reasons. Firstly to inform manufacturing volume as this would have a knock on effect on design. But also to take into consideration that maybe its not a good idea to focus the product solely on Oxygen but to make a design that can help a much bigger target market. This would also increase manufacturing volume, in term reducing individual part cost and therefore reduce the cost to the end consumer. 39

5.4 Use case storyboarding

A day in the life using a powered trolley One of my starting points for designing the product was storyboarding what an ideal use case would be like for someone if they had a ‘powered trolley’. This actually spurred lots of ideas that were directly led from what was learnt during the research phase of this project. This allowed me to categorise and think of how I would need to develop the design of this product, specifically the ‘Smart’ aspects of the trolley. A big challenge with choosing glide is making it understandable to the target market and so the development of a system that is beyond intuitive, almost intrinsic, was key to this project. Some concepts that came out of this process are described below:

An easy charge docking station that can be placed by the patients door so that recharging the trolley is not an extra effort.

A push release mechanism for the trolleys basket that can secure the patients bag in place.

The motor could be triggered by the trolley tilting as this motion is indicative of the user starting to walk.

There are times power assisting wont help such as lifting the trolley onto a bus, the design must remain as light as possible for easier lifting than the existing solution

5.5 System boundaries

Translating the user needs to component requirements The average gait speed of users for males and females aged 45+ was researched to inform the RPM that the motors would need to be set at to adequately assist in walking with the trolley.

21 Department of Veterans Affairs. (1993). Basic gait parameters: Reference data for normal subjects, 10-79 years of age. Journal of Rehabilitation Research. 30 (2), 210 - 223.

Research conducted by the Department of Veterans Affairs suggests that the average user walking speed is between 3.24 - 4.212 Km/h. This equates to between 0.9 - 1.17 M/s^-1. This equates to a distance of between 54 - 70 Meters per minute. With a wheel Diameter of 130mm each rotation of the wheel travels a distance of 0.408M to achieve the desired speed of between 0.9 - 1.17M/s the wheel would have to rotate between 2.2 - 2.8 times per second. In terms of RPM (revolutions per minute this told me that I needed to find a motor that works at a speed of between 132 - 172RPM. The most appropriate and widely available motor worked at 150RPM and this is what I sourced to begin with. I now needed to work out how much torque the motor required in use in order to carry the load the user would be carrying.

130mm

Working out the required motor torque To really enable this product to help the user it would also need to be able to carry other things on top of the oxygen cylinder. For this part the weight of the cylinder, conserver, carrier bag / handbag and weight of the actual trolley had to be taken into account. This came to a total of 11KG and and so to make sure that I had a motor with enough torque I used 15KG as a starting point. This would also consider the battery and electronic component weight.

Trolley ≈ 5 KG

Cylinder 3.5KG

42˚

102.7 N 42

Carrier bag MAX ≈ 2 KG

Conserver ≈ 0.4 KG

With a weight of 15KG the resultant force acting downwards from the axis of the wheel was calculated as 102.7N whilst the trolley was at the angle that was measured during research as the trolleys angle from the ground ( 42˚ ). This is the force that the motor would need to overcome. Converting this to a measurement of Watts was done by taking the force in newtons and multiplying it by the required velocity in M/s: 102.7 x 0.9 = 92.43 102.7 x 1.17 = 120

This told me that the required power in Watts was between 92.43 and 120. The most readily available motors never have such specific values and so I took 100 watts as a basis to work from.

22 Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr. gsu.edu/hbase/electric/elepow.html. Last accessed January 2014.

I know that the Motor uses 12V so in order to work out the current draw I used the equation below: P(Power) = V(Voltage) x I(Current) 100 = 12 x I 100/12 = I I = 8.3A This value is taken for a 15 Kilo loading and so in reality this could be scaled down to be more appropriate for the actuall 11kg load (based on estimations for actual trolley weight). It was difficult to find motors that had a specified torque in N/M but it was easier to find motors that had a labeled current draw and so on talking to Dr Antonio Vilches lecturer in Electronic Engineering at Brunel University, this method was used to find the correct motor. This also allowed me to work out what battery I would need. With the motor drawing a maximum of 8300Ma / h. The next thing to take into account was how long the average user journey was and for what period of time they are actually walking on that journey. I took the trip I took with Yolande as a reference as she explained that it was actually quite a long journey for her and by the time she got home she had to sleep from fatigue. All things considered Yolande was walking for a maximum of around 45 minutes on this 4 hour round trip (80 minutes spent on bus, 45 minutes spent in coffee shop). The time the actual motor would be on would only be whilst walking and this time was just 45 minutes so in terms of current usage: 8300 x 0.75 = 6225Ma So this told me that the battery needed to have at minimum a 6225Ma current storage to last one trip. However it would be a disaster for the trolley to run out of power half way through a journey if the patient did not charge it or if they stayed at a friends so to avoid the risk a 20,000Ma Lithium ion battery was bought. This would be able to last over 3 trips at a total of nearly 2 hours walking. 43

5.6 Anthropometrics

Trolley height 23

The main influence on the sizing of the product came from looking at anthropometric data. Initially the primary target market of users was considered, 45 - 60 year old women. The first sizes that I looked at were standing fist height and elbow height. These would influence the overall height of the trolley. The sizings were taken from the Delft University database â&#x20AC;&#x2DC;DINEDâ&#x20AC;&#x2122; and so the fact that the sizings come from a generally larger than average population were taken into account in the final design sizings. Here I translated the average sizes into what would effect trolley height based on a pulling angle of 40 degrees, which was highlighted in the initial research as the average angle the trolley would be pulled at to optimise weight balance and reduce force required in pulling.

Delft University. (2004). Anthropometric database. Available: http://dined.io.tudelft. nl/dined/. Last accessed 21 Jan 2014.

If the height of the trolley is optimal for each user they would avoid a bend in their wrist when pulling the trolley. This would make the design much more ergonomic and comfortable to use for long periods of time.

24 Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr. gsu.edu/hbase/electric/elepow.html. Last accessed January 2014.

31 - 60 year old females Grip circumference: 122mm This would translate into a handle diameter of 38.8mm 31 - 60 year old Males Grip circumference: 135mm This would translate into a handle diameter of 42.9mm Next I considered how the trolley could be designed so that users would find it much easier to lean on. This was something that I noticed from initial research as a problem with the existing product. Some users should have a walking stick and cant as a result of carrying oxygen. The product should serve as something to rest on. Here I looked at the different angles that users could lean on the trolley, finding the balance between a trolley height that would be easiest to pull and one that could allow for the user to rest their weight upon. Straight arm - Female users 30 - 60 years old

Height off ground at: 5˚ - 740mm 20˚ - 788mm 40˚ - 878mm Unfortunately if the trolley was any of these heights it would require a crook in the users wrist when being pulled around.

After observing some elderly people in public using walking sticks I realised that they do not tend to always lean on them straight armed, even though from a mechanical perspective this tends to translate more of their weight more easily due to the size of walking sticks and the fact that they (Much like my product) need to be leaned on and extended at an angle out in front of them. Instead they are designed to be leant on with a bent forearm. Here I looked into possible trolley sizes if the trolley was to be leant on with a bent forearm. Bent Forearm - Female users 30 - 60 years old

Based off of this data it was noted that the bigger the user (Male for example) the shallower the angle by which they could lean on the trolley. Therefore the exact height of the trolley should be governed by the biggest height you can get away with for leaning with the smallest of users. This would allow for the trolley to be pulled along comfortably by all but also make it feasible to lean on. This final trolley height should be no bigger than 1060mm

Trolley height < 1060mm

6.0 Electronics

6.1 Component selection Previous to this project I had little exposure to prototpying with electronics but in the end managed to successfully produce a few iterations of the prototype alone. My starting point for this was looking online at people who have developed similar projects with robotos using an Arduino. An Arduino is a single-board microcontroller that makes electronics more accessible. I found a few projects that created balancing robotos with a specific accelerometer called a â&#x20AC;&#x2DC;Memsic 2125â&#x20AC;&#x2122;. The code I found can be found in the references to the right. This formed the basis of the beginning of my project.

25 BelafonteBill . (2007). memsic 2125 accelerometer calcs - parallax. Available: http://forum.arduino.cc/index.php/ topic,40715.0.html. Last accessed 14 December 2013.

The components that I used for my first prototype are detailed below: Arduino Uno This is one of the most popular arduinos I chose this arduino based on the fact it is readily available and I could get replacements quickly at a relatively low cost.

l298 Motor driver This motor driver was recommended by a blogger on the Arduino Forum, it allows for control of 2 motors from an Arduino.

7805 Voltage regulator The motors required 12V but the Arduino has a max input of 5V, the voltage regulator was used to step down the voltage for the Arduino.

Memsic 2125 This was the initial accelerometer used for the project, it was chosen based on their being readily available code online for it.

Getting these ready made components saved time in the project as otherwise I would have had to make each of these seperately designing the PCBâ&#x20AC;&#x2122;s myself. This was actually a very long winded process sourcing these components they had to be ordered from China as they are not all available in the UK and on top of taking time to arrive with my first prototype I actually blew the first motor driver for a reason that to this day is unknown to me.

6.2 Circuit design V1 This circuit was wired up in a way to send 12V to the motor controller and 5V to the arduino through the 7805 voltage regulator. The aim of the first prototype was to use the Memsic 2125 which is a dual axis accelerometer to sense when the trolley is tilted and immediately send a signal to the motor to turn on, through varying the angle of the tilt the amount of torque in the motor was supposed to vary. The motor controller was responsible for this part of the code, this is actually a 256 bit motor controller and from testing I noticed that between 0 - 80 the amount of torque in the motor wasnâ&#x20AC;&#x2122;t even enough to overcome the friction of the gearing.

This left 80 - 256 for variations in motor speed but actually once mounted on my prototype trolley I found that anything less than 256 would not overcome the inital weight of the trolley wih oxygen and a carrier bag. Therefore the idea of tweaking the amount of torque based entirely off angle of tilt was flawed. The code for this design can be seen on the right. 49

This was actually a tough part of the project for me. My original intention was to outsource the technical aspects of the electronics but due to time contraints and a bad experience with a freelancer I was forced to learn to do simple code and put together circuits. The above picture was the first time I got something working after blowing one of the voltage regulators and the Lithium Ion battery failing on me. This spurred me on and I was keen to try it out.

6.3 Test rig V1

To make a test rig for my electronics I took an existing trolley, drilled lots of holes in it went into the metal workshop turned some motor connecting pieces, went into metal fabrication and made a bracket for my motor. Now I was ready to plug in and try out my circuit / see if my motor was able to carry the load.

I also made a cardboard prototype of the container within which the bags would be held and I was ready to go. In this initial test run I was using a geared motor bought in from China that was advertised as 150RPM but unfortunately it did not run at that speed! From putting some sticky tape on the wheel connecting it to the axis and counting how many revolutions passed in a given time I found it was actually running at only 60RPM. I did however learn some valuable lessons from this prototype: â&#x20AC;˘

â&#x20AC;˘

If the user wants to use the trolley without the motor turned on it actually becomes harder as they need to overcome the friction in the motor whilst pulling it. Turning with a fixed axis is a big problem and requires one wheel to turn faster than the other which makes it very difficult.

6.4 Circuit Design V2 With the second prototype I tried to overcome the problems faced with the initial code where I found that after the initial friction was overcome there was a short period where the trolley would travel faster than the users walking speed. I did this by changing the code to add in a time delay where the signal sent the motor controller varied between 160 - 256 in this period. This was intended to be so that their would be a more gradual and natural transition after the initial friction was overcome to aiding at a normal walking speed for the user.

In theory this worked and before putting it on the trolley it worked however when this was put on the trolley the gradual transition needed much tweaking and unfortunately this was mainly down to using a motor that was not fit for purpose at 60RPM, at this point in the project a variety of motors were purchased at varying RPM speeds including 100, 150, 200 to make sure that I got one that would be up to the job. By the time the motors arrived I had already moved on with my next prototype so this code actually got left behind although a better method was found eventually anyway this was good experience and learning nonetheless.

6.5 Test rig V2 As the design developed and learning from the pitfalls of the initial test rig a second was made. The main base went through a process of CNC machining, Milling and drilling and the turned components from the previous rig were reused. Other parts were repurposed from existing products.

6.6 Piezo Sensor At this stage in the design the electronics was getting more complex and I felt that to get it to a more usable finished stage I needed the help of someone. So with that a student of Electrical Engineering was brought on board to help with some coding. Here I was trying to think of a way of directly translating the users input into how much torque the motor gave off. The main idea being that as the user applied more force to the handle the trolley would react to that and supplement with motor torque to make this relationship of making the trolley easier to pull much more linear. The aim here was to strike a relationship between the force applied to the handle, and how much torque would be needed at the motor to supplement pulling the trolley. So when a user pulls the trolley with 20% of the overall force needed the motors supplement the remaining 80% but when the user only pulls using 10% of the force the motor supplements 90%. This was at first tested out using a piezo force sensor which actually proved an unreliable method of doing this as it only registered forces up to 1.5 Newtons and during testing actually broke. From this a force sensor with the ability to sense up to 10 Newtons of pressure was purchased.

6.7 Force sensor 26

With this forth prototype we learnt from the broken piezo sensor and bought in a small force sensor that was capable of taking loads up to 10N. (Pictured right) The idea moving forward with this prototype was to add the force sensor in the handle. The accelerometer first recognises whether or not the trolley is tilted passed roughyl 30 degrees. This ‘If’ function in the code then allows the force sensor in the handle to engage. If the force sensor in the handle then recognises a small force applied it sends a signal to the motor to turn on. The circuit was first wired up with a

‘3K’ resistor and so the relationship between force applied in newtons and voltage out was the most controlled that is possible with this sensor. However from initial testing we actually found that there wasn’t enough force to overcome initial friction to begin with and so this was later changed to a ‘30K’ resistor.

Interlink electronics. (2012). FSR 400 Data Sheet. Sensor technologies. 1 (1), 1-4.

Testing - Force sensor After the code was compiled the trolley went through several stages of testing. First the code with the force sensor alone was tried. The initial sensor parameters were not sensitive enough and as mentioned earlier there was some problems overcoming initial friction. The amount of force required in pulling the existing trolley is roughly 15 Newtons consistently. After much tweaking we were able to change the parameters on the force sensor so that through applying just ‘3N’ we were able to walk comfortably at 4.00 KMH (High end of average walking speed for target market). This was good news reducing the amount of energy expenditure needed by 12N. Testing - Force sensor + Accelerometer The accelerometer parameters were tested and the angle that the force sensor was engaged was far too low. Coding the parameters from how the arbritrary readings from the accelerometer (0 - 60) related to an actual angle was difficult and actually in the end the trolley was 40° clamped next to a mounted protractor so that the relationship between the arbritrary numbers and the real life angle was understood. With this the Arduino was programmed to engage the force sensor when it was tileted to 40°. Another issue that was found was that the motor will make an annoying high pitch noise from the internal friction in the gearing until enough voltage was sent to the motor to overcome this friction. One idea I had was to refrain from sending the signal to the motor unless it was already over the voltage that would overcome this friction. From testing the 8 bit motor controller we found this figure to be ‘80’ So another ‘If’ Function was added so that, even after tilt and measurement of force on the force sensor, unless the force was enough so that the signal to the motor was over 80 there would be no voltage sent to it. This cut out the annoying whirring but made the motor very jittery. 55

Smoothing the signal After the first prototype was put together Ludovic connected it to the computer via bluetooth to analyse the signals coming off the force sensor and the motor. They were originally coded to work together as the graph below shows. The 8 bit motor can take up to 256 individual signals that can be used to control the amount of voltage that is sent to the motor, the force sensor can take 512. How these work together to effect how much force needs to be applied to the sensor so that the users require minimal effort when pulling the trolley was what we spent a long time working on. Initially that meant testing with a newton meter until less than 1N was required to pull the trolley along. The parameters for how the motor and force sensor interacted together was refined to this stage where there are 4 points on the signal curve. After the initial prototype was put together, a bluetooth transmitter was added to the board. This Motor allowed us to monitor how the signal was really being passed between the force sensor and the motor. What we found was quite 350 surprising and can be seen in Force sensor the graph on the left. The actual 300 Initial signal variance - Motor / Sensor signical coming off the motor 250 (purple) and the sensor (Blue) was 200 quite eratic. 150 100 50

100

200

300

Post refinement variance - Motor / Sensor

Force sensor Motor

400

In practice this meant that the trolley was very jittery. It wasnâ&#x20AC;&#x2122;t possible to walk with it for more than 3/4 seconds without interference. Ludovic then added an â&#x20AC;&#x2DC;averagingâ&#x20AC;&#x2122; function to the code that read the signal every 2 seconds and averaged out the signal from the motor and sensor. This graph can be seen on the left.

After the addition of the ‘Averaging’ function in the code there were many undesired effects. The trolley would not simply stop when you released it instead for a small period of time, roughly 1 / 2 seconds the trolley would continue to move towards you, even backing me into the corner of my room! With this the averaging code was taken down to 5 milliseconds. This meant that the signal was more erratic, less so than the original, but at least the trolley did stop when the user would want it to. Another cause for the erratic nature of the trolley at this stage was also down to the angle at which the accelerometer engaged the force sensor (40˚). Refining the accelerometer After using the trolley for 15 minutes walking around campus I realised that during use you actually lift the handle up and down. Many times this actually caused the motor to cut off as i was moving beyond the 40 degree threshold level of 40° 20° the accelerometer. For this reason this threshold was lowered to 20 degrees. This also made stopping more convenient as at 40 degrees the trolley was stopping further away than was actually needed. At this stage the product was tested and the electronic aspects worked exactly how I wanted it to. The only issue at the moment was the mechanical aspect of how the force was applied to the sensor was unreliable. The force sensor requires such small amount of compression to achieve the force levels that it is sensitive to (as low as 0.1 Newtons) that designing something to apply such small levels of compression was the next challenge.

6.8 Final electronics - How it works 1.

At stand still the accelerometer and force sensor are dissengaged. Thus the motor is dissengaged. 2. Once the trolley is tilted 20 degrees the accelerometer allows the force sensor to engage. 3. If a force as low as 1N is applied to the force sensor the motor is engaged with a relationship described on the previous page.

Final Board After the prototype was successful with the arduino, it was moved over to an ATtiny microsprocesser. This is a simple $1 chip that can house up to 500 lines of code. It is much smaller but also alot more stable then the arduino. It could be the same chip that is used for mass manufacture because of the low price and durability.

Final circuit diagrams Curtousy of Ludovic Arnaud

6.9 Electronics implications on Design. Force sensor After implementing the force sensor, I started to consider the most reliable method of having it in the final design so that it would appropriately translate the force the user is applying. My first thoughts revolved around looking at how the user would hold the handle but for an 8mm sensor it was hard to place it anywhere that would reliably always pick up on the user pulling.

It was for this reason that this method of implimenting the sensor in the stem of the handle was come up with. By translating the force down the stem of the handle it does not matter where the user actually pulls the force would go directly to the compression sensor. Therefore translating a pulling force (Extention) to a pushing force (Compression) on the sensor.

Force sensor

7.0 Develop

7.1 Learning from others To start off with I bought a variety of other products currently on the market that had different mechanisms, uses and target markets to try and learn as much as I could from what was already out there. This excercise informed the design of the product in a big way and saved alot of time in prototyping. Shopping trolley aimed at the elderly One of the products that I analysed is a popular shopping trolley. The design has a fold out leg at the front which makes it useful for leaning on and very stable. It also has a large bag made from a rip stop Nylon that is hard wearing and durable. I found that this product was designed well for the target market although it is somewhat ugly and traditional. It does blend well with other products people use and so if someone used this for oxygen they would blend in well in public and their may also be less social stigma attached to using it. Industrial foldable carrying aid This product has an interesting geared folding mechanism that means as you push down the handle the base folds upright and ends up as what you can see in the image below. It was also very easy to rest on and I noticed that as the weight from the handle is translated to in front of the wheel instead of the axis of the wheels it was actually the most stable out of any of the trolleys to rest on. This was a noticeable difference and was the only trolley you could actually rest on without it running away from you.

The trolley backpack Although more expensive than the previous two products this one had a more flimsy construction and I found that it seemed like a much cheaper product. Part of this was down to the fact that the handle was entirely collapsible and had 4 stems which meant when fully extended it did wobble and was unstable. The single stem handle was also not very good to rest on and as it was joined to the axis of the wheels and when rested on it rolled away. I found that the backpack was uncomfortable to wear as you can feel the hard stem up against your back.

Standard trolley suitcase This product had a curved 3 stem handle which was not stable at all and although it did not have as much wobble as the trolley back pack it still did not feel very secure. The feet on the front of the trolley actally were sufficient enough to balance the weight and in use it did not feel as though it was going to topple at any point.

American oxygen backpack This backpack was imported from the states and is actually much nicer than the backpack that is given to the patients here. It has a simple design that only accomodates for the oxygen cylinder, a small eyelet to run the cannula out of and a PVC window for the user to see how much oxygen is left in the tank. It is light, comfortable to wear and when designing the backpack would serve as a good starting point to work up from. The only downside I can think of is that it doesnâ&#x20AC;&#x2122;t accomodate for the oxygen conserving device or anything else that the patient will no doubt be carrying so they would always be burdened with carrying this supplementary to a handbag filled with all their belongings and no way to use a conserver. 61

Third party oxygen backpack This is an oxygen backpack that you can buy from a company called â&#x20AC;&#x2DC;Air productsâ&#x20AC;&#x2122; they are a manufacturer of oxygen cylinders and other compressed gases. It is very badly designed! The hole for the cannula is on the opposite side of the product so the cannula has to wrap around to get to the user this is particularly awkward especially when considering that it is designed to be worn on both shoulders and so the cannula is left dangling out of the middle of the users backpack behind them. There is no window to see the gauge on the cylinder and because you have to unzip it from the bottom up if the user wanted to see how much they had left they would have to stop and put the bag on the floor otherwise they risk the entire tank falling out just to check how much oxygen is left. This is an example of how not to design the bag. Knomo Fargo - Stylish backpack Fargo is a well designed backpack by high end travel brand Knomo. It is not much bigger than the oxygen backpack from America but it has enough room for the cylinder a single shopping bag filled with potatoes, a small bottle of milk and still some room left. Although not tall enough this bag would serve as a good starting point in terms of size (depth / width) for an oxygen backpack redesign.

7.2 Design directions After much concepting it became clear that there were 3 real directions that this product could take. Each of them have their own benefits. These are explained on this page.

Slick cylinder Tubular oxygen carrier This concept was thinking about addressing the problem in the most minimal way possible. The current solution only makes it possible to carry the cylinder. This lightweight design would do that using a shell at the bottom that would fit nothing but the cylinder in a snug fashion.

All aboard

For all occasions

Powered shopping trolley

The all rounder

This concept looks to tackle the issues the user has more holistically. When they go out they are likely to do some shopping. Using this collapsible design they would be able to carry more than just oxygen.

Through incorporating the design of a special bag for oxygen that also allows for a shopping bag, this would actually satisfy most of the users trips.

7.3 Weighted factor scoring model These different concepts were now compared once again to the inital PDS. The Design that has the capability of meeting the most user requirements came out as the slick cylinder. Mainly down to how light the product has the potential to be. The Bigger powered shopping trolley could actually effect users negatively in many ways due to the additional weight, we have to consider when this device is being used in ways that it cannot be assisted such as whilst being lifting onto a bus etc. However I felt it was still important to let the users be able to carry an extra carrier bag. Most trips they go on could leave them having to carry something else back. To really make the most out of the powered trolley it would have to be able to assist with this also. Design direction It was with this that the direction became designing a device that allowed users to carry just oxygen in a lighter device than they currently use. However, also to give them the option to store a shopping bag in a semi permanent fashion so that if they need to they can, but doing so in a way that would not promote them to overload the device with more than they are physically capable of carrying. What if the battery was to run out and they were far from home? They would be left with more than they are physically capable of carrying alone and for a device to store much extra it would have to weigh more which would have a negative impact on all other PDS requirements.

7.4 Detail Design

Meeting all the users needs At this stage the thinking behind the design began to change. In an attempt to really lightweight the product the compartment at the front was removed and a hinged platform took its place. This new direction would be much lighter and have the capability of collapsing into a neat package. A bag designed specifically for oxygen, but also allow for storage of a single large carrier bag, could then be placed on this platform. This would mean the users can easily remove the bag and carry it for short trips and only use the trolley if they needed to on longer trips. This design also broadens the target market allowing users of any type of medical equipment or victim of any physcially debilitating disease could use the trolley in their aid.

Handle design The design for the handle had many considerations, but taking into account the target market and my initial research one thing that stood out was watching users want to lean on the existing trolley. This is made impossible by the fact the stem of the handle joins to the axle of the wheels so no matter what it inevitably wants to role. Through this observation the concept of moving the stem of the handle to in front of the wheel came about.

Current handle position

Redesign

This would stop the wheels rolling when leaned on. through simple cardboard prototyping this was proved to work.

Double stem handle From testing different trolleys with single and double stems it was immediately noticeable that the double stem handle was much more sturdy and looking at other products that target this market it became clear that this was a design decision they all made, and for good reason.

Translating force directly to the ground To keep the most stable design that is structurally durable the force from the handle being leant on should be translated directly to the ground. This would ensure minimum stress on the axis of the motor and make for a more reliable design.

Finite Element Analysis This design was tested using FEA analysis with different loads to see if it would buckle under too much stress. The design was fixed at the two points that would connect to the ground, the base of the foot rest and the axle that the wheels would be connected to. A load was then put on the location that the handle would be. The red arrow in the diagram of the mesh on the right indicates the direction of gravity. This analysis did show some stress build up but even at a 100kg loading the force translating directly to the ground did not cause an excess of stress that would lead to the part fracturing or buckling. For the sake of the FEA analysis the model was simplified to just the main base and the foot rest. The material for the Main base and feet were taken as ABS. The main base has a wall thickness of 3mm, the feet were solid ABS. In the actual design the feet would be overmoulded with vulcanised rubber which would also spread the load more efficiently reducing the likelyhood of material fracturing further.

10KG Load

50KG Load

100KG Load

The front rest For designing the front foot rest I went through a few different design iterations. First designing methods that would be most stable from looking at shopping trolleys designed for the elderly. I first started trying to replicate the fold out mechanism that these trolleys have, I then designed one with just the metal bar.

I was worried at this stage that I was overcomplicating the design. So I conducted an FEA analysis of just having a simple rubber foot rest. I took the points at which the front is hinged and the base of the rubber foot as the fixed points. I then placed a distrubted load with different weights onto the top plate (where the bag / oxygen would be). What I found was that a vulcanised rubber footrest would buckle under quite low forces. So I changed the design to an ABS foot with a rubber overmould like the feet on the main base. This design can be seen in the screenshots below, it was able to take the load with no problem, infact what I did find was an issue with the bottom plate that the bag would be put on, the stresses were so much that the plate began flexing. At this stage the design for the bottom plate was incomplete so I ignored this.

Force distribution

10KG

Meshing

20KG

After prototyping the design with the handle moved to in front of the wheels and the rubber feet directly beneath the handle it was already much more stable than the existing design. Considering the front rest would actually just be taking most of the weight from the bag / oxygen that would be placed upon it it doesnâ&#x20AC;&#x2122;t need to be too structural, that would just be unneccesarily overcomplicating the design. The design decision was to have a rubber foot on the end of the rest.

7.5 Aesthetic

Timeless and relevant It was key to develop the aesthetic aspects of the deisgn to appeal to the target market. So much so that they want to use the product. But also to help it blend in by making it fashionable people are much less likely to notice it as something different whilst using in public. Colours / materials / Finishes To decide on a CMF pallete I first looked at brands that this age group like. I contacted Salma Shah a retailer buyer for John Lewis who suggested a variety of brands to look at that are most popular and desirable with this age group. The types of brands that were considered the most desirable had a clear trend in terms of CMF and I began to start picking from these to develop my own product aesthetic.

Timeless - Brown leather

Modern - Polished Aluminium

Smart - Moulded ABS neutral colours

A material that ages well, is desirable to the target market. Expensive so would be used sparingly.

A lightweight structural material. Used for the neccessary elements of the design such as the handle / hinges.

A flexible and strong material that speaks of the embedded technology over a normal trolley.

7.6 Feedback At this stage the design was presented to the user focus groups that I met whilst conducting initial research. In particular three ladies in this group that fit into my primary target market. The design was also shown to the medical research doctor Sam Kon, among some industry design proffessionals and lecturers at Brunel.

27 Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr. gsu.edu/hbase/electric/elepow.html. Last accessed January 2014.

Users - Positive The users really liked the product aesthetic. They described it as elegant and classy. However I was worried that they may have been saying this out of being polite, I did get the impression when I met them during intial research that they were very polite by nature and would have some difficulty giving negative feedback. Doctor - Negative Sam thought the design was very much like a luggage trolley. “It doesn’t look like something that belongs in a hospital”. Even though this was my initial aim when designing this trolley it did make me feel that I had gone too far on the spectrum and the product needs to feel more secure and look more trustworthy and helpful. Industry Designers - Negative They thought that for a product that houses ‘Smart trolley’ capabilites the product visual language did not reflect its function. You wouldn’t walk up to this trolley and expect it to be motorized with sensors. Lecturers - Negative The most important feedback came from Dr Ian De Vere. He made me realise that after taking so many considerations to keepi this product modular so that it could be used by a larger target market, I had actually made it less useful for COPD users carrying medical oxygen.

7.7 Modular product architecture The product needs to be usable by a mass market, not just oxygen users. But it must be perfect for each of these individual use cases. Through designing a one size fits all product there is so much compromise that the product becomes less useful for any of these markets. It was with this in mind that the concept of a modular product architecture was developed. The entire product can be used for all of the possible target markets. The only part that is changed is the basket at the front which could be designed to be removable.

Removable basket concept This product could then be purchased with the basket for each individual use case. So if you want to carry an oxygen cylinder you just buy the basket that is ideal for doing that. This gave me more freedom in the design to make it much more useful for this particular target market without closing off the posibility of the product branching out into other markets that its function could be useful for. I began by designing the locating mechanism that would be used for the basket.

Designing the basket The first thing I designed with the basket was the locating mechanism, how it connects to the rest of the product. This was designed to locate the basket to avoid anyone putting it on the wrong way around. The basic shape for this was concieved and tested using a quick cardboard prototype. This shape can be seen below, it was implemented into the base part of the product.

This would be held in place using a cheap and commonly used push latch mechanism. This was chosen for those reasons so that it would be cheap to implement and manufacture and because it is commonly used designing it to be more reliable would be much easier and there would even be a case for not having to manufacture this part ourselves but buy this part in and design the base and the basket to fit a ready made product, that has already been tested.

Design aims - Modular design with interchangeable basket - Aesthetic more reflective of the embedded â&#x20AC;&#x2DC;Smartâ&#x20AC;&#x2122; trolley technology - Less like just any luggage, an aesthetic that is more honest to its application. Implementing redesign How the basket merged with the rest of the product was an aspect of the design that I developed through rigorous sketching and 3D CAD. It was here that much of what became the final 6 face design was developed. This was very much an iterative process.

BASKET REMOVAL PROCESS 80

Designing the basket The initial outlook on designing the basket was that I could make it much smaller as a result of not having to cater for all purposes. From the users perspective they need to: • • •

Be able to carry the cylinder on its own Be able to carry the cylinder in its bag Be able to also carry at least one large carrier bag (2kg) with or without the bag.

This redesign would allow the users to carry the cylinder on its own easily. The basket has been designed so that it would be able to carry a custom designed bag. The problem with this design is it doesn’t allow the users to carry a cylinder and carrier bag on their own .... 130mm

130mm 130mm

7.8 Design review At this stage I went back to the URS with the design.

Must accomodate for the cannula tubing At this stage the design did not have any particular method of storing the excess cannula cable.

Must be easier to replace the cylinder Without any screwing needed the redesign takes on average 11 seconds (13 participants) 71 seconds quicker using less force in the process

Must fit the conserving device Using the oxygen conserver bag placed nearly behind the tank this user requirement is met.

Must require less force in use Using the Newton meter the new design requires just 3 Newtons to pull. 12N less than the original.

Must be more aesthetically pleasing At this stage the design di not have a proven improved aesthetic over the original. Although this isn’t difficult due to the purely utilitarian nature of the original design the aim was to make something the users want to carry. At this stage this wasn’t the case. Improvements to make In order to meet the set requirements the design needs to: • • • 82

Accomodate for a carrier bag when the user is carrying the cylinder naked Be more aesthetically pleasing for the target market Must accomodate for the cannula tubing

Accomodating the extra carrier bag To redesign the basket to meet the requirements of carrying an oxygen cylinder and a carrier bag I started out with some simple cardboard prototyping. This made the problem much more tangible and actually made me realise, with the cylinder in the middle it wasnâ&#x20AC;&#x2122;t feasible to have the carrier bag in the basket. Putting this on the trolley made me quickly realise no one would want there shopping that close to the ground.

This gave me the idea of utilising the free space on the other side of the handle of the trolley. I could design a small collapsible bag to go here that would allow the user to carry their shopping in a more safe and trustworthy location if they donâ&#x20AC;&#x2122;t have their oxygen backpack.

This would be collapsible so that when not in use it sits flush against the handles on the back of the trolley. Prototyping showed that as this bag would be so close to the axle of the wheels and the foot rest it did not add a significant weight impact due to moment of being raised.

Redesigning the basket After a design development session with Dr Farnaz Nickpour, we decided to make the size of the oxygen bag wider at the base, it was ill concieved to design a bag that was so small at the base and wider at the top, it would require alot of unneccessary structure and the space was available on either side of the old basket design to allow for widening. It was with this the design changed to what you can see below. 300mm

130mm 130mm

After further carboard model prototyping a size was found that is able to fit a large carrier bag and oxygen cylinder. This size also fits a large handbag or standard 300mm wide backpack but in comparison to the design above it is slightly taller. Through making the basket slightly bigger it gives us more freedom in the bag design for which I 300mm envision creating a handbag esque backpack to carry the oxygen and a carrier bag. With the basket this big the user can also fit a 170mm large carrier bag, this now means that the user would always be able to carry the minimum requirement set earlier on in the project of the oxygen cylinder and carrier bag.

Getting feedback on the aesthetic A few options for the design aesthetic were developed and through users and Salma Shah (retail buyer at John Lewis) I was able to obtain feedback from 34 women within the 45 - 60 age group. Not all with COPD but I felt it was important to get the feedback of the general population as the publics perception of this product was key. 85

8.0 Final Design

8.1 Branding - Classy / Timeless “Brand desire is the key to product success.” Peter Walshe, Milward Browne

Mobi - Fashionable assistive products People hate needing help and feeling like they need to rely on something / someone. Even if they know a product can help them the way in which the product does this decides whether or not it will actually be used. Existing assistive products impose themselves on the user, by their very nature only adding to the burden of needing assistance in the first place. Mobi aims to change this. Give the user something so desirable they would want it even if they didn’t need assistance.

Logo design A variety of logo designs were created to reflect the product / brand values. These were then showed to 34 women within the target market age group and each voted for which they prefered.

Mobi Mobi. 17 votes

6 votes

MOBI MOBI 11 votes

0 votes

The final logo design was chosen based off this feedback. The logo options were presented in conjunction with the product design options with the aim of getting a more congruent result.

8.2 Final design aesthetic Based off the feedback from 34 women in the target age group this was the final design that recieved the most votes. Black was the most popular colour choice as it was described by many as be able to match with any other clothes that they may wear.

8.3 Materials

28 Cordura. (-). Cordura ultra light fabric. Brand fabric technologies. 1 (1), 1.

Aluminium Aluminium would be used for the handle assembly. It is a cost effective and light material, roughly 3 times lighter than steel which is used for the existing oxygen trolley. Although steel is roughly 3 times stiffer than Aluminium my FEA analysis actually showed there was no problem with using 1.50mm wall thickness aluminium tubes for the handle. ABS Acrylonitrile Butadiene Styrene has a high impact resistance, wears well, is very flexible from a manufacturing perspective, is widely used and cheap. From an aesthetic perspective at higher temperatures it is capable of achieving high levels of gloss finish but is also mouldable with different surface VDI textures etc ... From an environmental perspective ABS is very hard wearing and so would prolong the life of the product. Cordura - Ultra light Nylon Fabric Research into different types of fabrics was conducted to find which was best suited to this application. It was narrowed down to Rip stop Nylon and Cordura (Kodra). Cordura was chosen based off superior tear strength and ability to withstand higher hydrostatic pressure. The material is also very light and as it is made from a base of Nylon 6.6 it would surely last the product life.

Parts Mobi would manufacture 5

Sensor housings Material: ABS Process: Injection moulded

Handle cover 8 Material: Cordura Process: Bought in cut and sewn

Handle Material: Aluminium Process: CNC Tube bending

Handle top stem Material: Aluminium Process: Extrusion

Consever bag Material: Cordura Process: Bought in cut and sewn

Connecting bracket Material: ABS Process: Injection moulded

Handle bottom stem Material: Aluminium Process: Extrusion

Elastic holder Material: ABS Process: Injection moulded

Rubber bumper Material: Butadiene rubber 2mm sheet D cut to size Process: Bought in and

Lid Material: ABS Process: Injection moulded

Oxygen basket Material: ABS Process: Injection moulded

Base E Material: ABS Process: Injection moulded

Rubber base Material: Butadiene rubber 2mm sheet Process: Bought in and cut to size

D NOT FOR MANUFACTURE

DATE

SIGNED

16 Apr 14

DATE

VOL (cc) SIGNED

DRAWING PURPOSE

Feet Material: ABS TOLERANCES Process: Injection moulded

Design review

Mobi

3D DATA VERSION

16 Apr 14

SHEET

SCALE

1:1

DIMENSIONS IN - mm DRAWN TO BS 8888

PROJECT

Power assisted trolley COMPONENT NAME

Assembly DRAWING No

01-001

LATEST ISSUE

9.0 Design for Manufacture

9.1 Optimising parts Parts were organised by manufacturing process and I went through making sure that they adhere to the limitations of that process. Injection moulding I went through the parts making sure there was relatively uniform wall thicknesses, and draft angles bigger than 1 degrees especially on the basket. As you can see below there is quite a large cavity on this part which would require a big draft angle to be ejected out of the machine easily and without risking part warping. I have added a 3 degree draft to all inside faces. The other simpler parts were also modified to suit this manufacturing process. However, at this stage in the design feedback from a manufacturer would be essential and would be part of the project further development.

CNC Tube bending A CNC tube bending expert called â&#x20AC;&#x2DC;Pipecraftâ&#x20AC;&#x2122; were contacted for manufacturing advice on the handle part. A Radii of 40mm is commonly used and so would make manufacturing this part cheaper and easier therefore this radii was implemented in the product design. Extrusion The aluminium tube would be very easy to manufacture using an extrusion process.

9.2 - Costing - Manufactured components Injection moulded parts Billy Lai of CNM moulding China was contacted (A contact through placement) to recieve intitial quotes on my injection moulded parts and assembly. The quotes were based off tooling cost and a product run of 39,000 units with mostly 4 cavity moulds.

Lid Tooling cost: £4,306 Cost per unit: £1.41

Base Tooling cost: £12,650 Cost per unit: £3.94

Elastic holder Tooling cost: £1,426 Cost per unit: £0.76

Connecting bracket Tooling cost: £1,112 Cost per unit: £0.65

Sensor housing - 2 Tooling cost: £495 Cost per unit: £0.29

Oxygen basket Tooling cost: £16,594 Cost per unit: £4.59

29 Shanghai Metal Corporation. (2014). Aluminium tube 5052 . Available: http:// www.alibaba.com/product-detail/AluminumTube-3003-5052-5083-6005_222108801. html. Last accessed 10 Apr 14.

Feet - 2 Tooling cost: £785 Cost per unit: £0.41

Extruded parts

Handle tube - Aluminium 5052 Cost per unit (2280mm): £0.35

CNC tube bending Standard radii used Cost per unit: £0.12

Sewn parts Unforunately getting quotes for sewn parts in China is not so easy. The quotation here was given to me through East end manufacturing - a London based clothing manufactuer. This is much more expensive then it would be. Total cost of manufactured components per unit: £17.02 Conserver bag Sewing cost per unit: £ 3.80

Assembly cost per unit: £4.92 (excluding sewn bag)

9.3 Costing - Sourced components All quotes for costing were based on an initial manufacturing volume of 39,000 units, the number of oxygen users in London alone. 150mm Wheels Quantity: 2 Price: $0.50 per unit Supplier: Jianqing, Shanghai M3 x 10mm countersunk screws - Brass Quantity: 4 Price: $0.001 per unit Supplier: Weire, Shenzhen

30 Jianqing. (2014). 6 inch wheels. Available: http://www.alibaba.com/product-detail/6inches-wheel-for-wheelchair_1438387496. html. Last accessed 11 Apr 14.

31 Weire. (2014). Slotted brass countersunk screws. Available: http://www.alibaba.com/ product-detail/Slotted-Brass-CountersunkScrew_731882926.html. Last accessed 11 Apr 14.

M3 x 20mm countersunk screws - Brass Quantity: 4 Price: $0.003 per unit Supplier: Weire, Shenzhen 3mm Blind rivets - Brass Quantity: 8 Price: $0.001 per unit Supplier: Jiesheng hardware industry, Shenzhen 12V high torque (up to 11kg - cm) motor Quantity: 2 Price: $1 per unit Supplier: Wenzhou Zhengke Electromotor Co. Ltd 0.1 - 10N Force sensitive resistor Quantity: 2 Price: $0.5 per unit Supplier: Shenzhen Sunhokey Electronics Co. Ltd

Jiesheng hardware industry. (2014). Best selling foreign brass rivet. Available: http:// www.alibaba.com/product-detail/Bestselling-foreign-Brass-rivet_1577809479. html. Last accessed 11 Apr 14.

33 Wenzhou Zhengke Electromotor Co. (2014). 12V high torque motor. Available: http://www.alibaba.com/product-detail/12v150rpm-dc-gear-motor-28mm_1111985489. html. Last accessed 11 Apr 14.

34 Shenzhen Sunhokey Electronics Co. Ltd. (2014). FSR400 Force Sensitive Resistor Force Sensor. Available: http:// www.alibaba.com/product-detail/ FSR400-Force-Sensitive-Resistor-ForceSensor_1109471657.html. Last accessed 11 Apr 14.

MMA7361 Accelerometer Quantity: 1 Price: $0.30 per unit Supplier: Wenzhou Zhengke Electromotor Co. Ltd

35 Wenzhou Zhengke Electromotor Co. Ltd. (2014). MMA7361 Accelerometer Module Tilt Slant Angle Sensor. Available: http://www.alibaba.com/product-detail/ MMA7361-Accelerometer-Module-Tilt-SlantAngle_728277453.html?s=p. Last accessed 11 Apr 14.

ATtiny 85 Microprocessor Quantity: 1 Price: $0.10 per unit Supplier: Top source, Shenzhen

36 Top source. (2014). Original new ATTINY85. Available: http://www.alibaba.com/productdetail/Original-new-ATTINY85_598306317. html. Last accessed 11 Apr 14.

Sprung touch latch Quantity: 1 Price: $0.13 per unit Supplier: Gerbon Hardware Accessories, Shenzhen.

37 Gerbon Hardware Accessories. (2014). Sprung touch latch mechanism. Available: http://www.alibaba.com/product-detail/ Spring-Touch-Latch-Catch_1438010880. html. Last accessed 11 Apr 14.

38 Wuxi Zhuocheng Mechanical Components Co., Ltd.. (2014). stainless steel ISO7380 socket button head screws. Available: http://www.alibaba.com/product-detail/ stainless-steel-ISO7380-socket-buttonhead_1648705952.html?s=p. Last accessed 11 Apr 14.

M3 x 10mm socket button head screw Quantity: 8 Price: $0.001 per unit Supplier: Wuxi Zhuocheng Mechanical Components Co., Ltd.

39 Jingdong rubber. (2014). 2mm Viton/ FKM Rubber Sheet. Available: http://www. alibaba.com/product-detail/2mm-VitonFKM-Rubber-Sheet_1566621825.html?s=p. Last accessed 11 Apr 14.

2mm rubber sheet Quantity: 54 grams Price: $14 / Kg = $0.75 per unit Supplier: Jingdong rubber, Hebei, China.

Cordura fabric Quantity: 0.128m2 Price: $3m2 = $0.38 per unit Supplier: Suzhou Texshow Textile Co., Ltd

Suzhou Texshow Textile Co., Ltd. (2014). 1000d cordura printed fabric with flame retardant coating. Available: http://www. alibaba.com/product-detail/1000d-corduraprinted-fabric-with-flame_1800584177. html?s=p. Last accessed 11 Apr 14.

Total cost of bought in components per unit: $5.69 = ÂŁ3.39 Total cost per unit including bought in components (excluding assembly with electronic components):

ÂŁ25.33 95

10.0 Review

10.1 Measuring success against original PDS

Product Design Specification

Here I took a look back to the original PDS to see how far the project has come.

Mobi meets this requirement Explanation of terms Must

Mobi failed to meet this requirement A mandatory requirement that constitutes a failed development if not met. If it is agreed that a requirement cannot be met, the requirement must be development adjusted. The project has not reached this stage yet - Further

Want

A specification requirement with importance This is nohigh longer relevantto product success needing a high level of commitment to

achieve this requirement, but failure (especially missing target by a small percentage) will not

a failure of the development. Here I took a lookconstitute back to the original PDS to see how far the project has come. Prefer

A requirement with medium importance to product success, but the requirement will not be formally verified. This may be due to lack of access to relevant equipment for testing etc.

Ideal

A requirement with low importance or a guiding nature. This may also apply to specifications that will not be able to be met in time frame of project.

1. 1.1 1.2 1.3 1.4 1.5 2. 2.1 2.2

3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10

User requirements Force required in transporting oxygen should be less than existing solution consider the use of a cannula cable consider the use of an airflow conserving device reduce average time to replace oxygen cylinder reduce average time to assemble carrying device require less energy to pull up stairs than existing solution consider other items used such as handbags that users carry consider use with public shopping trolleys Be stable enough for users to rest on when tired Be able to operate entirely with one hand

4. 4.1

Purchaser requirements Product should be collapsible for ease of storage and distribution

Must Want Want Want Prefer Height < 380mm Width > 110mm -

Must Must

15.87 N 82 sec 36.2 sec 18.32 J -

Must Must Must Want Want Want Prefer Prefer Prefer Ideal

Want

3.6 3.7 3.8 3.9 3.10

4. 4.1 4.2 4.3

5. 5.1 5.2 5.3 5.4 5.5 5.6

6. 6.1 6.2 6.3 6.4

18.32 J -

Want Prefer Prefer Prefer Ideal

ISO 14971

Want Prefer Ideal

1050 mm < 65 mm -

Must Must Must Want Prefer Prefer

Must Want Want Prefer

4.75 mm BS585 2630 mm - 5째C to 40째C -15째C to 40째C -

Must Want Prefer Prefer Prefer Ideal

8. 8.1 8.2

Service life Withstand minimum of 5 years of use (average patient time using oxygen) Product be easy to maintain

Must Prefer

9. 9.1 9.2 9.3 9.4 9.5

Must Want Want Want Ideal

10. 10.1

Based on number of oxygen users in the UK, 6000 units should be manufactured PA

11. 11.1

Market Price / Manufacturing cost Target market price and manufacture cost will be based on chosen concept

Must

12. 12.1

Standards and specifications Relevant standards and specifications will be based on chosen concept.

Must

Manufacturing volume

Abbreviations COPD NHS MM

Chronic obstructive pulmonary disease National Health Service Millimetres

11.0 Further Development

The aim of this project was the development of a more considered carrying solution for medical oxygen. The redesign of the trolley enables the users to carry their oxygen with them using less force, giving them space to store the oxygen conserver, cannula and whilst being much more aesthetically pleasing. However the product is incomplete without the bag that would be used alongside the trolley. The bag would be used to carry the oxygen when the trolley is not needed, for example on short trips. It would also hide the oxygen much better whilst it is in the trolley, addressing the psycho / social issues much better. 11.1 The oxygen bag Extensive research looking at existing bags on the market has already been carried out. There are design aspects of this that would influence the design of the bag such as: •

•

A neatly placed hole for the cannula that allows for it to come around the wearer very discretely. A small window to enable the patient to see how much oxygen is left in the tank.

The bag would be designed so that it doesn’t look like a backpack but instead a stylish sling bag. Much like the original design for the bag concept shown on the right. It could adopt the Mobi aesthetic in terms of colour scheme and use of Cordura as a main material. The bag itself has many considerations like how it can store excess cannula, the oxygen conserver, an extra carrier bag safely alongside an oxygen tank and many more that would become more apparent from further design and development. This is an entire project in itself.

11.2 Testing the market With the bag designed the product would be at a point were the function could be tested with the target market to see if users think that it could viably benefit there lives over the existing trolley. COPD patients undergo a 6 minute walk with oxygen equipment when they are first prescribed it, I watched one of these at the start of the project, it would be a reliable method of testing to see if patients are able to walk further in 6 minutes with the powered trolley. Quantifying energy expenditure that a user goes through whilst using oxygen equipment and then comparing how much energy they could have saved with a powered trolley will give justification to the product and decide whether or not it should be explored further. From an Aesthetic perspective research has already been conducted and the current developed product is liked by the users, this aesthetic could be explored further with a bigger sample size to get a more realistic representation of whether the target market would actually like the product. Anonymous feedback would be preferable to get a more unbiased answer. With this completed and with quanitifiable measures of the products success in reducing patient energy expenditure levels and being more aeathetically appealing to this target market, the product will be at a stage to approach oxygen providers such as ‘Air liquid’, ‘Air products’ and ‘BOC’. A cost / benefit analysis would be conducted to find out how much more patient adherence would increase their expenditure on cylinders. This could be a big influencing factor for oxygen distributors and would be a big reason for them to stock the product. If they were to then express interest Mobi would be worth developing further to manufacture stage and product launch. At this stage the product could be developed further using an open design approach to make it easier for the target market to understand.

11.3 Designing in the clutch 41

In order to use the trolley in both a powered and non powered state the motor would need to be connected to some sort of clutch mechanism. When the user turns the trolley ‘off’ to use it without assistance the clutch would dissengage the connection with the motor rod and allow the wheels to freewheel. There are widely used existing parts designed for the size of 12V motor that is being used in this project but due to time constraints I was unable to order and implement one into my design in time. A company called ‘Polyclutch’ sells a product that would work for this particular application. It is designed to fit the motor rod straight through the middle. It would also be worth considering a magnetic clutch, which may be more reliable based on not needing any mechanical components to engange and disengage the clutch. The choice would have to be made based on whether or not there is a real cost benefit in investing in a magnetic clutch which may be more reliable. Flowserve are a company that sell a 12V magnetic clutch that could be used in this application. A link to their product can be found in the references.

100

Polyclutch. (-). Series 16 miniature slip clutch. Available: http://www.polyclutch. com/slip-clutches/clutches/mechanicalslip-clutches/series-16-slippers#tabs-1. Last accessed 14 Mar 14.

42 Flowserve. (2009). 12V magnetic clutches. Available: http://www.flowserve.com/files/ Files/Literature/ProductLiterature/Pumps/ pss-90-20.18-e.pdf. Last accessed 14 Mar 14.

11.4 Designing the charging dock The current design has taken consideration for an induction charging dock.

Designing the charging dock The current design has taken consideration for an induction charging dock.

However due to time constraints I was unable to actually design this. This aspect of the product is absolutely crucial as it enables the user to easily charge the device. It was part of my initial storyboarding and it is something that could be kept near the patients front door as a reminder to always put it on charge as they come and go.

101

11.5 Complete design implementation of mechanisms The touch latch mechanism that would be integrated into the basket and base so that it can be easily secured in place needs to be chosen and the internal design changed to secure this in place. Product testing on different touch latches would have to be carried out to find one that is secure enough to bear the max loading of 10KG that would be placed in the basket. Complete testing of this with a prototpye to find out if there is a problem with the basket accidentally dissengaging would have to be carried out, and if this is an issue it would need to be designed around to avoid this becoming a problem. The handle is designed to collapse, preferably on a rack and pinion mechanism, so that it is easily adjustable to different heights for different users in order to be most ergonomic. Unfortunately due to time constraints in the project I was unable to implement this into the design although I did find the right parts that could be bought in. Although a simple version of the of the mechanism that would be used in the handle to transmit the pulling force to the force sensor was made for the prototype, this has not been fully designed into the final product yet. Thorough testing to ensure that the correct amount of force is being transmitted to the force sensor and that it is not being overloaded would have to be conducted. Through dampening the force, like I did in the prototype using layers of 2mm rubber, the users could pull as hard as they want on the handle, such as if they were to pick up the loaded trolley by the handle without breaking the force sensor.

102

11.6 IP65 - “dust tight” and protected against water projected from a nozzle. As the trolley is intended for outdoor use it would need to be compliant to IP65. This would ensure that it can endure use outdoors through puddles, drink spillages etc... This could incorporate the design of a seal around the main base, lid and motor axle holes as these are the areas through which water could seep through damaging the internal electronic components. Controlling heat within the enclosure - Temperature testing Although the main base and lid would need to have a relatively high tolerance or sealed enclosure to avoid excess water penetration it would still need to allow a level of airflow through the product to avoid the circuit and motors overheating. This could involve the use of a ‘Gore-Tex’ or similar type material implemented in vents which would allow air through but still hold out moisture.

103

11.7 Tolerance analysis Before the product could be manufactured the ready for manufacture parts would have to undergo a thorough tolerance analysis to make sure even if the seperate components were made under or abover tolerance the whole assembly would still fit together. This may involve incorporating slots in place of holes and changing very slightly dimensions on parts. To make sure that the assembly definately does fit together in the end the engineering drawings may specify â&#x20AC;&#x2DC;Metal offâ&#x20AC;&#x2122; during the first round of tooling on parts that are most important. This would ensure that when the CAD data goes to the tool maker they are particularly careful not to take more material off those dimensions, as once material has been taken off the mould all of the parts would come out bigger and there is no going back. In the case of mould making it is always best to take off less material at first, test, and then based on an initial round of manufacturing decide whether or not to take off more material.

104

Final thoughts Aesthetics was a big part of this project. Creating something that would incur less social stigma through better design. Unfortunately due to the time constraints of the project and the untimely death of the my closest contact through my focus groups, I was unable to take my model to my original research participants to get their final feedback. I will however pursue this post report deadline as i know they are excited to see the product. Looking back its hard to believe that this entire journey started from personal experience of having asthma. Unlike many other students who started the year out with a product in mind I did in the beginning feel worried that I would not reach a good level of design and may end up working on a research project. However instead when I look back over the project I realise that I got exposure to a broad range of the design process. Taking secondary research through to a realised works like and looks like design has been very hard work in the relatively short amount of time that I have had. But looking back I wouldnâ&#x20AC;&#x2122;t change any of it and I feel like through my major I have taken much learning from Brunel design.

105

References Stoller, J. Panos, R., Krachman, S., Doherty, D., Make, B. (2010).Oxygen therapy for patients with COPD. 1 (1), 179 - 187. WHO. (2013). Chronic obstructive pulmonary disease (COPD). Available: http://www.who.int/mediacentre/factsheets/fs315/en/. Last accessed 30th Sep 2013. Thomas L. Croxton , William C. Bailey. (2006). Long-term Oxygen Treatment in Chronic Obstructive Pulmonary Disease: Recommendations for Future Research. Available: http://www.nhlbi.nih.gov/meetings/workshops/lott-wksp.htm. Last accessed 11th October 2013. Dr. Mark A. Earnest MD, PhD. (2002). Explaining adherence to supplemental oxygen therapy. Journal of General Internal Medicine. 17 (1), 749 - 755. Libby, P. Braunwaldâ&#x20AC;&#x2122;s Heart Disease 8th Edition, W.B. Saunders, 2007. Hung, W. American Journal of Respiratory and Critical Care Medicine, July 15, 2009; vol 180: pp 134-137. Arne M, Lundin F, Boman G, Janson C, Janson S, Emtner M.. (2011). Factors associated with good self-rated health and quality of life in subjects with self-reported COPD.. Primary Care Research Unit, County Council of VĂ¤rmland. 10 (1), 511 - 519. T. Eaton, J.E. Garrett, P. Young, W. Fergusson, J. Kolbe, S. Rudkin, K. Whyte. (2002). Ambulatory oxygen improves quality of life of COPD patients: a randomized controlled study. European Respiratory Journal. 1 (1), 306 - 312. Benjamin Dillon, Phone interview. Air Liquide, 06 Oct 2013 Dr. Mark A. Earnest MD, PhD. (2002). Explaining adherence to supplemental oxygen therapy. Journal of General Internal Medicine. 17 (1), 749 - 755. Mackenzie, F.T. and J.A. Mackenzie (1995) Our changing planet. Prentice-Hall, Upper Saddle River,NJ,p288-307. (After Warneck, 1988; Anderson, 1989; Wayne, 1991.) WHO. (2013). Chronic obstructive pulmonary disease (COPD). Available: http://www.who.int/mediacentre/factsheets/fs315/en/. Last accessed 30th Sep 2013. Richard Marsh, Telephone interview. Air Liquide, 03 Nov 13 Drs. van Durme, Van Pottelberge, Joos, and Bruselle. (2009). Prevalence, Incidence, and Lifetime Risk for the Development of COPD in the Elderly. The Rotterdam Study. 135 (2), 600-684. American lung association. (2013). Taking her breath away, the rise of COPD in women. Available: http://www.lung.org/assets/documents/ publications/lung-disease-data/rise-of-copd-in-women-full.pdf. Last accessed October 22nd 2013. Lindsay Smarthill. 2014. Air Liquide - Portable oxygen users. Interviewed by Lindsay Smarthill [radio] Mobile Phone, January 09th 2014. Oxygen therapy for patients with COPD. 2014. Current Evidence and the Long-Term Oxygen Treatment Trial, 01 (138), pp. 179-187. NHS uk. (2012). Chronic Fatigue Syndrome. Available: http://www.nhs.uk/conditions/Chronic-fatigue-syndrome/Pages/Introduction.aspx. Last accessed 13 February 2014. MS society. (-). What is MS?. Available: http://www.mssociety.org.uk/what-is-ms. Department of Veterans Affairs. (1993). Basic gait parameters: Reference data for normal subjects, 10-79 years of age. Journal of Rehabilitation Research. 30 (2), 210 - 223.

106

Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html. Last accessed January 2014. Delft University. (2004). Anthropometric database. Available: http://dined.io.tudelft.nl/dined/. Last accessed 21 Jan 2014. Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html. Last accessed January 2014. BelafonteBill . (2007). memsic 2125 accelerometer calcs - parallax. Available: http://forum.arduino.cc/index.php/topic,40715.0.html. Last accessed 14 December 2013. Interlink electronics. (2012). FSR 400 Data Sheet. Sensor technologies. 1 (1), 1-4.

Hyperpysics. (2011). DC Electric Power. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html. Last accessed January 2014. Cordura. (-). Cordura ultra light fabric. Brand fabric technologies. 1 (1), 1. Shanghai Metal Corporation. (2014). Aluminium tube 5052 . Available: http://www.alibaba.com/product-detail/Aluminum-Tube-3003-5052-5083-6005_222108801.html. Last accessed 10 Apr 14. Polyclutch. (-). Series 16 miniature slip clutch. Available: http://www.polyclutch.com/slip-clutches/clutches/mechanical-slip-clutches/series-16-slippers#tabs-1. Last accessed 14 Mar 14. Flowserve. (2009). 12V magnetic clutches. Available: http://www.flowserve.com/files/Files/Literature/ProductLiterature/Pumps/pss-90-20.18-e.pdf. Last accessed 14 Mar 14.

107

Acknowledgements Dr Farnaz Nickpour - Lecturer in Design - (Major project first supervisor) For invaluable support and guidance throughout the project. For keeping the users centric, for questioning decisions, for wonderful insight and for always making time to see me. Research Colin Hawkey - COPD patient Organiser of Middlesex hospital Pulmonary rehabilitation sessions, Colin was so enthusiastic about my project he went out of his way to make sure I met oxygen users and always arranged for me to get feedback. Unfortunately Colin passed away before the project was over and was unable to see the final design. Yolande Grace - COPD patient Dr Samantha Kon Dr Ann Nolan Denise Williams Industrial Design Nick Reddall - Senior Design Engineer - PDD Graham Lacy - Technical Director - PDD Simon Lamason - Senior Industrial Designer - PDD Dr Ian de Vere - Head of Design - Brunel University Electronics Dr Antonio Vilches - Lecturer Electronic Engineering - Brunel University Ludovic Arnaud - PHD student, helped code and design the final electronic system. Thomas Maltby - PHD student Manufacturing Mr Paul Barret - Technician - Plastics workshop - Without Paul I wouldnâ&#x20AC;&#x2122;t have a final model. Mr Peter Bird - Chief Technician â&#x20AC;&#x201C; Woodworking Workshop For everything else! Mr Leslie Botwright - Technician, Stores - Brunel Univeristy

108

109

Mobi. Power assissted trolley TAALIB MINHAS