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Hydrobionics Master thesis of Per-Johan Sandlund & Hans Jakob Føsker The Oslo School of Architecture and Design, Spring 2014
Students: Hans Jakob Føsker Per-Johan Sandlund
Supervisors: Steinar Killi Etienne Gernez
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Students
Hans Jakob Føsker, 29
From Oslo, Norway Mail: hj.fosker@gmail.com Phone: +47 40648591 Web: www.Hydrobionics.no
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Per-Johan Sandlund, 29 From Nordmaling, Sweden Mail: pjsandlund@gmail.com Phone: +46 70 2227953 Web: www.Hydrobionics.no
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Table of contents
Intro 6 Broad research 16 Influential projects
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Scope definition
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Concept ideation
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Focused research
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Concept development
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Result 102 User secenario
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Reflection 116
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Image: wallpaperswide.com
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Intro
We propose an open source bionic AUV to allow hobbyists to conduct deep ocean exploration and in the process help further ocean science as a whole.
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Structure of the report We start with a brief introduction. After the introduction we will outline the research that has influenced this project. Then we will define the scope of our concept before taking you through our development phase. After the concept development phase, we will sum up our result and offer our own reflection on the project.
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Land 29%
Explored 5%
Ocean 71%
Not explored 95%
The Pacific ocean seen from space. Image from google earth.
The oceans
The worlds oceans cover 71% of our planet, yet scientists estimate that only 5% of the water has been explored1. Of those 5%, most of what we know is really only about the surface, or waters shallow enough for human divers. The world record for deep diving is currently at 534 m2. Consider for a moment what that means when the ocean has an average depth of 4.3 Km.
1 http://mashable. com/2013/09/25/ocean-vs-space/ 2 http://en.wikipedia.org/wiki/ Deep_diving
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Their importance
The oceans contain a complex interdependent biosphere about which we understand very little. We do know, however that we are completely reliant on it as the algae supplies our atmosphere with 70% of its oxygen. It’s the ocean, not the rainforest that keeps us breathing 1. Yet, through ignorance or disinterest our species is destroying it at an alarming rate through overfishing, carbon emissions and other stress factors. 2
1 http://education. nationalgeographic.com/education/ activity/save-the-plankton-breathefreely/?ar_a=1 2 http://edition.cnn. com/2013/03/22/world/oceansoverfishing-climate-change/
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Edith Widder was able to capture a live giant squid on camera, by simply being quiet. Image: deepseanews.com
Image: http://www.noaanews.noaa.gov/ stories2005/s2370.htm
Todays equipment
Ocean research equipment today is extremely expensive, excluding all but the best funded teams from doing work on deep sea exploration.
Infiltrate
Todays deep ocean equipment is typically very loud. In an environment that is normally dead quiet, noisy equipment scares off wildlife before researchers get the chance to observe it. Edith Widder applied a change of tactics to be the first ever to capture a live giant squid on video; simply by being quiet.
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Like amateur astronomers
We envision a future where amateur ocean explorers will contribute with data for the scientific community in the same way amateur astronomers do today.
contributions1. Hopefully a similar organization and culture could help us uncover the mysteries of our oceans in the near future.
Amateur astronomers help out with data collection by providing many smaller telescopes in addition to the relatively few but large telescopes available to professional astronomers. Organizations such as the American Association of Variable Star Observers, help coordinate these
1 http://en.wikipedia.org/wiki/ Amateur_astronomy#Scientific_ research
Targeting the hobbyist market
By creating an AUV that is low cost and open source, this project aims to provide the opportunity for hobbyists to perform ocean exploration, democratizing access to the worlds ocean floors.
Image: http://www.iau.org/news/ pressreleases/detail/iau0904/
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Our project We propose a bionic, autonomous underwater vehicle or AUV to infiltrate subsea habitats. Our AUVs morphology is largely based on a tuna, and has been given the name AUTuna. Based on our research we have come to believe that if we make a quiet fish looking robot, aquatic life might ignore it giving it access to undisturbed sea creatures in their natural habitat.
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Broad Research
How can we as industrial designers contribute to ocean research? We started this explorative project with a very broad approach. We posed the question, how can we as industrial designers could contribute to ocean research, thinking that it would probably amount to designing a sailing robot. What follows is the research and findings we made that have influenced the direction of this project. Knowing nothing about the industry we tracked down some individuals who we thought might give us the necessary insights.
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Roberto De Almeida Until recently Roberto worked for marineexplore.org, an ocean research database with aggregated data focussing on normalizing and visualizing all openly available ocean data. His position there gives him a unique birds eye view of the field. He said there are a lot of black holes in his maps. A lot of areas remain completely unknown, and that rather than obsessing about data quality, it’s more important to get something out there, and refine it later.
“Any data is better than no data!” He also mentioned that existing knowledge is largely unavailable to the public, residing on local hard drives in researchers offices. “A lot of research exists only on the computer of the researcher who gathered it”.
is often in a format that is very hard to process. Either as a lengthy scholarly journal paper, or as a spreadsheet with raw data values without any visual representation. These things make it very hard for anyone without intimate knowledge of the work to make any sense of it.
He went on to point out that what data is made available to the public,
“Any data is better than no data!” – Roberto De Almeida
Roberto De Almeida Ocean Data Engineer at Marinexplore
Image: marinexplore.com
Marineexplore.org aggregates and visualizes all openly available ocean data.
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Peter Keen
Peter is an operational oceanographer, meaning he makes a living out of launching and retrieving, as well as designing custom ocean research equipment. His opinion on existing technology, is that because most of it has been developed for the offshore oil & gas industry with completely different needs in mind, it is generally bad for ocean research. Overall, todays equipment lacks a more holistic approach in the design phase, which today is done by engineers solving specific tasks.
Peter Keen on what should be our main focus:
“Whatever you do will be great�
Peter Keen Operational oceanographer. Here seen in Antarctica. 22
Image: keen-marine.com
Image: keen-marine.com
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Influential projects
Influential projects The following is a summary of the projects we found in our research that have influenced our diploma.
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Image: wallpaperswide.com/
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Graham Hawkes holding a scale model of the Super Falcon submersible. Image: Balint Porneczi/Bloomberg
“To truly appreciate and understand the oceans and it’s inhabitants, we have to be able to move like them: Gracefully and gently.” –Graham Hawkes
Graham Hawkes’ Super Falcon
Graham Hawkes is a marine engineer and undersea explorer who has a different approach to how we as humans should explore the ocean and its inhabitants. We saw a National Geographic documentary1 featuring among others mr Graham Hawkes who had lots of comments on how we until just recently have treated the oceans as a 2D object. It also baffled him how
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we’ve been diving with noisy motors and blinding lights into the waters expecting to see things. “To truly appreciate and understand the oceans and its inhabitants, we have to be able to move like them. Gracefully and gently.” His philosophy made us believe more strongly in the value of animal movements, and want to incorporate them into our project.
https://www.youtube.com/ watch?v=ZElzys4AhNs from 37:25
The Super Falcon in action. Image: Tony Wu Photography
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Edith Widder on how to explore the oceans with the help of quiet platforms:
“Attracting animals rather than scaring them away”
Edith Widder, Image: teamorca.org
Edith Widder & the Giant Squid In 2012, Dr. Edith Widder was part of a team of researchers who employed new tactics to capture video of a living giant squid. Although mankind has known about this creature for hundreds of years, no one has ever seen one alive until Widder’s team caught one on video.
In a TED Talk, Widder also comments at length on how we are scaring off wildlife with our noisy equipment. 1
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http://www.ted.com/talks/ edith_widder_how_we_found_the_ giant_squid
Their approach was to mimic the bioluminescent light show of a common jellyfish that it displays when attacked. This is a last ditch resort intended to attract something bigger than what’s attacking it. The giant squid knows that when the light show is visible, there is food near by.
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First giant squid ever captured on video. Image: Deepseanews.com
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Image: http://www.digitallife.gr/wpcontent/uploads/2012/03/lions04.jpg
Image: https://plus.google. com/112302113750019621047/photos/ photo/5819182310430285106
Infiltrate the Habitat
An example of a land based project that uses unobtrusive infiltration to capture unique footage, is the Beetlecam Project. The Beetlecam is an RC buggy with an armored shell mimicking a turtle. Lions mostly ignore turtles, so the Beetlecam is able to capture images that would be impossible to capture by other means.
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Open rov ready for shipping Image: Openrov.com
The Open ROV project
Eric Stackpole’s open source Remotely Operated Vehicle is a low budget Do It Yourself counterpart to the commercial Remotely Operated Vehicles used among other things for maintenance work in the oil industry. In a New York Times article the Open ROV is heralded as the future of ocean exploration. -”There are only a few teams on this planet that can undertake multimillion-dollar projects to build full ocean depth research technology” - Victor Zykov, director of research at the Marine Science & Technology Foundation.1
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http://bits.blogs.nytimes. com/2012/05/28/a-mini-submade-from-cheap-parts-couldchange-underwater-exploration/?_ php=true&_type=blogs&_r=0)
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This lead us to believe that an open source & low cost platform would be a far more valuable contribution than something geared towards well funded research teams.
An Open rov checking out a shipwreck. Image: Openrov.com
”There are only a few teams on this planet that can undertake multimillion-dollar projects to build full ocean depth research technology” - Victor Zykov, director of research
at the Marine Science & Technology Foundation.
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Research findings There are a lot of problems that we could have made a project about. Peter Keen and Roberto De Almeida’s remarks confirm that. But in our opinion the biggest problem, and the one we think we are best suited to address, is the industry’s lacking ability to generate public interest for their work.
NASA’s mars rover curiosity taking a selfie on the surface of mars. Image: http://en.wikipedia.org/wiki/ Curiosity_(rover)
I’m gonna explore the surface on mars. But first, Let me take a selfie...
Public interest
Scientific journal papers are not an engaging format, and lose the battle for attention to things like the Mars Rover, Space X or Mars One. We think this is a major problem because lack of public interest means that policy makers looking for voters will not be as concerned with matters concerning the oceans. However, there are a few projects that have demonstrated the ability to catch the public eye. On one end of the financial scale is James Cameron’s Deepsea Challenge 1, and on the other is the OpenROV project 2.
The submarine Deepsea Challenger at the deepest known point on Earth, the Mariana Trench. Piloted by the Canadian movie director James Cameron Image: npr.org
l! Coo
The Deepsea Challenge was a manned dive to the deepest known point in the ocean, 10,908 meters down into the Mariana Trench off the coast of Guam. This project generated lots of interest with several Youtube videos each with up to half a million views. The OpenRov Project is an open source system developed to let amateurs and hobbyists explore shallow waters from a small boat or pier. Their Youtube channel has a few tens of thousands of views, and they were featured in the New York Times tech blog. Edith Widder’s discovery of the giant squid was a Youtube blockbuster, being reposted countless times generating millions of views, as well as being featured on CNN, the Discovery Channel, TED.com and a number of other channels.
! Yes
Bo
or in g ...
Years of measurements in Alaska Presented in a data sheet. Survey made by the Institute of Marine Science at UAF’s School of Fisheries and Ocean Science Image: http://www.ims.uaf.edu/gak1/
1 http://deepseachallenge. com/ 2 http://www.openrov.com/
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o!?! Hell
Remotely operated vehicles (ROV’s) are noisy and scare off the wildlife they are trying to observe.
Video
What they have in common is engaging video of locations, environments and/or animals otherwise completely inaccessible to most people. We also think that OpenROV in particular attracts attention because now all of a sudden, the average Joe can go out and explore on his own without any funding. Given the fact that new species are discovered on every deep sea dive1 we believe that the more cameras in the water, the better.
1 http://mashable. com/2013/09/25/ocean-vs-space/ 36
Blend in
From Graham Hawkes and Edith Widder’s work we surmise that the use of quiet infiltration will produce video of natural animal behaviors, rather than video of a fish escaping the ROV that filmed it, or simply no fish at all.
Biomimetics3
When aiming to unobtrusively infiltrate an environment it really only makes sense to try to move like something that might belong there. Further there are many performance benefits to be gained from tapping into 3.8 billion years of trial and error.
3 What is Biomimetics? From Wikipedia: Biomimetics or biomimicry is the imitation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms biomimetics and biomimicry come from the Greek words bios, meaning life, and mimesis, meaning to imitate. A closely related field is bionics, in short the study of biomimetic robotics.
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Scope definition
Scope definition We are going to create the first stepping stones for an open source, low cost bionic AUV platform. We will focus primarily on the biomimetics of form factor and kinematics, and leave advanced programming and electromechanical engineering to someone more capable. Although there are many measurements that can be taken that would be useful to scientists, we have decided to focus on video as our primary data format because video of strange marine creatures is what seems to most effectively hook the publics attention.
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Image: wallpaperswide.com
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What else is out there?
RoboTuna
A robotic tuna Massachusetts Technology.
Googling far and wide we found only a few projects that have created bionic submersibles.
made by Institute
the of
Robotic tuna made in 2009. A project by the mechanical engineering school of ETH Zurich. (Swiss Federal Institute of Technology).
“Built to simulate the action of a fish, the RoboTuna was designed by American engineers at the Massachusetts Institute of Technology, (MIT), to see if a robot sub could mimic the way tuna swim. The metallic tuna proved to use less energy and to be more maneuverable than other robot subs.”
It was designed to explore the use of bio inspired locomotion principles.
Text above from London science museum
Narotuna
h t t p : // w w w . n a r o . e t h z . c h / p 2 / narooriginal.html
Image: https://www.facebook.com/ pages/Naro-nautical-robot
http://www.sciencemuseum.org.uk/ images/manualsspl/10328063.aspx Image: http://www.sciencemuseum.org.uk/
MIT Soft robotic fish
Naro Taratuga
A robotic sea turtle, also made by the mechanical engineering school of ETH Zurich.
Also made by researchers from MIT This prototype was made primarily to showcase the capabilities of soft robotics. The robot uses compressed carbon dioxide as the energy source for its inflating actuator. While extremely agile, it’s limited to a maximum of 20 to 30 strokes and would not work at all below a few meters in the ocean as the compressed gas would not expand.
h t t p : // w w w . n a r o . e t h z . c h / p 2 / narooriginal.htmll
http://newsoffice.mit.edu/2014/softrobotic-fish-moves-like-the-realthing-0313 Image: https://www.facebook.com/ pages/Naro-nautical-robot
Image: http://newsoffice.mit.edu/
Our contribution
Although these projects are most impressive, none of them are of much help if you are wanting to create one for yourself. They make it seem like such projects require a team of engineers working for a year and have not made their work available for public use. None of them can dive deeper than the bottom of a swimming pool either. Our contribution will be to make and share a robot that is designed to go deep and intended to be recreated by individuals on a limited budget. 40
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Concept Ideation
Concept Ideation The following section covers our exploration of biomimetics and targeted research into various marine propulsion systems and biorobotics.
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Image: wallpaperswide.com
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Building a test tank
A 700 liter test tank. Hans Jakob assembling the test tank.
The tank was built out of plywood, tarp and duct tape.
Testing
In order to test ideas and iterate quickly, we built a 700L test tank. It formed the basis of our test routine where we built lots of low definition physical sketches of marine animals. This proved a very efficient method of validating a concept. What follows are the test notes from this phase.
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Actuators
The wire displayed on this image is Flexinol-brand nitinol, a nickel-titanium shape memory alloy.
Flexinol wire shrinks about 5% when heated to 100°C. Here its heated with an electric current
Muscle wire
Nitinol
Our robots needed muscles. Preferably, our robots would have silent muscles. Nitinol, also known by brand names such as Flexinol or Muscle-wire, is a nickel-titanium shape memory alloy that returns to a “remembered state” when heated. Flexinol specifically increases its cross sectional area, thereby shortening in length. The contraction is remarkably strong, and the contraction speed is limited only by how fast it can be heated. Conversely, the relaxation rate is directly linked to how fast the wire cools after the current is removed. And best of all, they’re dead silent.
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In our case we got some 300mm x 0.1mm strands that contracted fully in 0.1 second, drawing 0.7 A at 12V. It relaxed in 2 seconds after the current was removed. The required temperature for it to contract is ~100C which for our wires required a minimum of 200mA in air at room temperature. The force generated by one strand was 222g which is quite impressive for something that weighs less than 1g. Because it contracts, it is possible to measure through its electrical resistance how much it has shortened. A long wire will have more resistance than a shorter wire. Using that information, one could regulate the current accordingly so that a large burst is supplied to contract the wire quickly, and then just pulse current intermittently to maintain the desired position.
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Nitinol in cold water
Because the nitinol works on temperature changes, the wires showed absolutely no reaction when submerged in 4°C water and supplied with 12V. But, when we coated the wire with a thin layer of silicone, it reacted just as if in air at room temperature. Too much silicone, and the relaxation took a lot longer.
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Prototyping with servos
Although nitinol is awesome, we settled on using servos for our prototypes because of both programming and hardware simplicity. With a servo, one can precisely specify an angle to a hundredth of a degree, and the servo will send its output shaft to that angle. With nitinol on the other hand, we would have to measure the resistance of several lengths of
wire to determine whether or not the resistance difference is linear or not. If it’s non-linear we would have to create lookup tables for every step of a given contraction resolution. Servos also come complete with mounting geometries making for very easy assembly, where nitinol would require constructing a custom skeleton for every actuator.
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Jellyfish
Jellyfish
We were eager to test a concept around a jellyfish, because of it’s very simple kinematics. The kinematic complexity is so much lower than the others, that the jelly was the only water test we did using flexinol. The jellyfish ran a very simple contractrelax cycle, of 0.5 seconds of contraction phase, followed by a 3 second relaxation phase. The pulling force of the flexinol was mostly absorbed in the length axis of the silicone surrounding the wire without generating much flexion, as there was no rigid material to resist the wire. Therefore, although the wire contracted very strongly the jellyfish mantle had very little force. Even when we used the 0.3 mm wires, the jellyfish was quite weak, even though it pulled a staggering 9 A during each contraction phase.
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Conclusion
The jellyfish was indeed simple, but its incredible inefficiency disqualified it from further testing. It was both the most power hungry and the slowest of our tests.
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Twister 1
Twister 2
Twister 1
Twister 2
An early concept inspired by penguins winged propulsion. The twister is a mechanically simplified version of a penguin or a sea turtle where a single servo oscillates large wings to create thrust.
Conclusion
In the water it fought itself more than it generated thrust. Also, we had no way of steering it.
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To give the twister a second chance we attempted to streamline the body by removing two fins, and giving it a tapered rear end.
Conclusion
It seemed better but to compensate for the missing fins the wingspan had to be so large that it wouldn’t fit in the tank. Requiring such large control surfaces in relation to it’s own size is a weakness. Also, we still had no obvious way to steer it.
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Squid
Squid
The balloon squid. We had hunch that a squid would be very efficient. This was the only electronics free sketch model consisting of one balloon filled with water, with a 1 mm jet nozzle. The squid managed to swim 4-5 lengths in our tank which equates to 12-15 meters on one filling of the balloon. It was very slow, but also very graceful. We tried adding two more 1 mm holes to the nozzle. That increased the speed somewhat, but cut the range in half.
Conclusion
The squid didn’t seem very efficient, as it had to move extremely slowly to cover much of any distance. We left the concept as we couldn’t figure out a way for the balloon squid to refill itself without using a pump of some sort.
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Eel
Sketching with servos.
Not that impressive.
Eel
We were keen to test a fish like creature, to compare it to the other forms of locomotion. The eel sketch was a creature made from cardboard, duct tape, automotive clay and condoms that used 9g submicro servos for motion.
Conclusion
Besides from being a visual atrocity, the robot was poorly balanced and veered off to the side. Testing various fin geometries, the results were that a fin covering the posterior 2/3 of the robots body proved the most efficient. This is in line with research we did later which showed that what this robot did was replicate how eels swim. Another conclusion is that the 9g submicro servos aren’t strong enough to deform the skin needed to waterproof them.
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Whale
Resisting reaction forces
Without pectoral fins, the whale just moved its midsection up and down while the fin remained stationary.
Whale
Eager to test with stronger servos, the whale bot was the first sketch model we did using high power servos. We bolted the servos together, forming the tail of the robot, and ziptied that to the bottom of a 1.5 L soda bottle forming the body. To save energy, we opted for waterproofing the servos themselves, rather than encasing them in a waterproof shell.
We added flat boards to serve as pectoral fins. At first we placed them where we thought pectoral fins should be, near the front of the robot, but this just changed the pivot point of the wobble. We moved the fins to the apex of the curve created when the robot was at max deflection to any one side. This drastically reduced the wobble, and more of the force directed backwards
Pectoral fins
=Force
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Whale Fin One
1mm PET sheet. Too stiff and did not flex to provide an appropriate pitch angle
Speed and deflection
We experimented with different settings for individual servo deflections, starting with 45 degrees. That proved too much as the whale bopped up and down more than it swam forward even though it had fins made to counteract that.
Lowering the angular deflection to 30 degrees removed most of the wobble, and the robot swam nicely forwards.
Whale Fin Two
PET sheet, Zipties and tape fin. This design proved to be more efficient as the tape flaps and PET sheet spine flexed enough to pitch the fin in the water
Conclusion
The results were very promising, but the whale would require additional fins to steer laterally in the water.
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Fish
Buoyancy
Fish
Spurred on by our success with the whale, we simply flipped the whale bot to one side, changed the tail fin and made it into a fish.
To take the complexity of neutral buoyancy out of the equation we added a large bottle as a flotation device. Once in the water, the bottle fish far outperformed everything we had tried so far.
PET Foil test
By simply folding a 0.5mm PET sheet into a foil and dragging it through the water we could feel a dramatic difference in lift generated in comparison to a flat board. We added the foil fin to the bottle fish.
Foil shaped tail fin
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The fish steers by shifting its tails center point.
A flatter body resists more lateral force.
Body shape
Although the bottle fish had dorsal fins to counteract the lateral force of the tail, the body moved significantly back and forth. We attribute this to the cross section of the body being cylindrical, and as such not
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generating much lateral resistance. Studying pictures of fish, we observed that their bodies are most often quite flat, providing a lot of surface area to resist the lateral force of the tail fin.
Steering
We added steering capabilities by shifting the center point of the servo oscillations left or right.
In theory, a whale robot could be made just as effective, but we prefer the lateral agility gained from steering by shifting the servo centers, rather than using additional fins.
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Oil filling of servos...
A note on water and pressure proofing
Dealing with DIY underwater electronics was not surprisingly, very difficult. We realized early on that if our final prototype was to last for more than one test dive, there could be no half measures. Everything needs to be properly sealed with greased o-rings, and any structure with an air cavity needs to be strong enough to resist the water pressure without deforming enough to break the seals.
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Emptying servos of oil...
Therefore, all air pockets should ideally be oil-filled. For our purposes, oil can be considered incompressible and will not decrease appreciably in volume at any pressure found in any part of the ocean. We oil filled the interior of our servos intending for them to be pressure proofed, but the oil added so much friction in the internal motor, that one servo fried itself. We had to drain all of them and forget about our intended deep dive for this prototype.
Another less obvious factor is the impact of thermal expansion rates of different materials. If the components forming a seal are assembled at room temperature with significantly different thermal expansion coefficients, one will shrink more than the other when submerged in cold water. That could lead to the seal being broken.
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Various tests of active buoyancy control. Non of them matched our demands of energy efficiency or being pressure neutral.
A note on buoyancy
Controlling buoyancy is a very energy efficient way to dive or ascend, at least near the surface. To do this, the submersible must increase or decrease it’s total water displacement without changing its weight. This is trivial near the surface, but great depths it becomes extremely challenging as the pressure can be as high as 1100 Bars. That means that to increase it’s displacement,
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the submersible has to overcome a force of 1100 kilograms for every square centimeter of surface area of the volume it needs to displace. Sharks provide a simple solution to this. -Flight. Sharks have no swim bladders, and use hydrodynamic lift over their pelvic fins to maintain desired level in the water. This is the exact same mechanism that keeps man made aircraft flying.
Ballast tanks
The concept is simple. Pump water into the tank until its no longer buoyant. The ballast tank system worked beautifully in our test tank, but can not be used at any great depths with out great difficulty. This is because the pressure outside the ballast tank would require the pump to be incredibly powerful, and the tank would have to be made extremely strong so as to not implode.
Cooled oil
When in water temperature, oil is cooled significantly sink as it contracts decreases while its unchanged.
of the same buoyant. When oil in water will and its volume weight remains
Our second concept on active buoyancy was to control the temperature of an oil volume to change its buoyancy. Regular cooking oil is almost pressure neutral, and the concept worked, but required way too much energy to cool down the oil volume. We tried to lower the temperature with a battery and a thermoelectric cooler. This failed even though we had an excessively powerful battery.
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Focused Research
Focused Research
The following section sums up the research that has been in some way useful for the end result. How it has been implemented in the shaping of the AUTuna is shown in the concept development section.
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Positioning
Communication
Underwater GPS is not possible. That means, that any positioning has to be done by acoustic pinging, or by inertial measurement. Because one of our goals is to be as unobtrusive as possible, we have ruled out acoustics. An Inertial Measurement Unit or IMU can calculate position remarkably accurately. It works by calculating speed through measuring accelerations. Any acceleration will mean that the speed has changed. As long as one keeps track of speed and heading over time, one can work out positioning. This example from Youtube1 shows an experiment where someone tracks the position of a foot with impressive accuracy.
Wireless underwater communication is acoustic only, which means introducing noise and running counter to our intent. Also, acoustic communication only allows for very low bandwidth stuff like a string of numbers or a text. Video streaming is quite impossible. Therefore all the ROVs are tethered to provide a real time video feed to the surface.
The tether of an ROV spooled up on deck. Image: http:// teacheratsea.wordpress.com/ tag/cable/
1 https://www.youtube.com/ watch?v=6ijArKE8vKU Tracked data from a foot walking a spiral staircase Images: https://www. youtube.com/watch?v=6ijArKE8vKU
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You can always add lead
Another insight, was that one should always strive to make the submersible as buoyant as possible. A bit counterintuitive, but the idea is that different missions may call for different payloads. More battery, a large sonar, a heavy camera system, etc. To make it neutral and balanced in the water once the instrumentation has been fitted, “You can always add lead”.
London
In order to gain insight, we went to London for the Oceanology International Exhibition. An annual subsea industry trade show, where all the manufacturers of ROVs, AUVs and other underwater products come to show off their goods. The key take away from the exhibition, was that cables are a serious problem. Not only do they seriously hamper the maneuverability of the ROV, but they have a practical maximum length of 4km, which if you think about it is an absurd amount of cable to deal with. The spools required are often much larger than the ROV itself. But the real problem is that the cables create a lot of drag in the water, and provide currents with a lot of surface to pull off of. That means that the
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longer the cable, the stronger the ROV’s thrusters needs to be to pull them. The stronger the thrusters, the more power they need. The more power the cables need to conduct, the larger their cross section has to be. The larger the cables, the more drag they create…. This spirals out of control at about 4 km. Because of this we decided that our robot needed to be autonomous. An AUV with no cable can be made much smaller and more manageable than a deep diving ROV, and as long as it can withstand the pressure, it can dive all the way down to the bottom of the Mariana Trench.
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Fish anatomy
Body deflection
Fish Swimming forms
Biologists have classified the swimming kinematics of fish who swim by oscillating their tails into five categories. From the Wikipedia article on fish locomotion1: Anguilliform: Seen in eels and lampreys, this locomotion mode is marked by whole body deformations in large amplitude waves. Both forward and backward swimming is possible by this type of swimming. Subcarangiform: Similar to anguilliform swimming, but with limited amplitude anteriorly that increases as the wave propagates posteriorly, this locomotion mode is often seen in trout.
Anguilliform
Carangiform: Body undulations are restricted to the posterior third of body length with thrust produced by a stiff caudal fin Thunniform: The most efficient aquatic locomotion mode with thrust being generated by lift during the lateral movements occurring in the caudal fin only. This locomotion mode has evolved under independent circumstances in teleost (ray-finned) fish, sharks, and marine mammals.
Subcarangiform
Carangiform
Speed
Thunniform 0 km/h
130 km/h
1 http://en.wikipedia.org/wiki/ Fish_locomotion
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Fish fins
We did extensive research on fin shape in relation to the animal’s top speed through the water. From that research it follows that what all the fastest creatures have in common is that their fin, or rather hydrofoil is shaped with a high aspect ratio, low relative tip area, and a lunate planform. The best example of an animal that follows these rules this is the black marlin, which has been measured by a BBC camera team to speeds of up to 128 kph.1
1 https://www.youtube.com/ watch?v=mD7t057XIi8 78
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Focused research Summary.
Image: http://whalesightings.blogspot. no/2011_09_01_archive.html
Humpback whale flippers
Further we came across some research on the bumpy flippers on humpback whales that concluded that the so called tubercles, i.e. the bumps on the leading edge of the humpback whale flipper makes them perform better1. They list up some remarkable numbers for performance improvement over a smooth edged hydrofoil of the same size and planform:
1 http://scitation.aip. org/content/aip/journal/ pof2/16/5/10.1063/1.1688341
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-8% more lift -32% less drag -40% higher angle of attack before stall. An article from design-engineering. com2 on the study cites a windturbine that improved it’s annual energy output by 20% just from switching to tubercled blades.
Image: http://www.canadianmanufacturing.com/wp-content/uploads/2010/11/10-oct-whalepower-tubecle-hydrofoil-360.jpg
Aquatic locomotion It was pretty obvious once we made a fish robot, that the oscillating foil of a fish is far superior to any of the other forms of marine animal propulsion. We later found some research on the matter that confirms this. The energy efficiency of marine animal propulsion is measured in what is referred to as Froude Efficiency. It is a dimensionless number, or rather a ratio. It is the ratio between power input over power output.
A Froude Efficiency of 1 would mean that 100% of the energy put into the locomotion system would be converted into forward motion with zero loss. Also known as impossible. A Froude Efficiency of 0 would mean that 0% is converted into forward motion and most likely that the actuator has malfunctioned. According to wikipedia’s article on aquatic locomotion1 and the journal article “Oscillating foils of high propulsive efficiency”2
1 http://en.wikipedia.org/wiki/ Aquatic_locomotion, 2 http://dspace.mit.edu/ bitstream/handle/1721.1/25614/ Triantafyllou-1998-Oscillating.pdf
The various locomotion systems rank as follows: Jellyfish: 0.09 Very bad. Squid: 0.29 About three times better than a jellyfish, but still rather inefficient. Thunniform Swimmer: 0.87. Very efficient and outperforms most man made propulsion systems which typically land at 0.7. We will of course base the kinematics of our final prototype on this swimming style.
2 http://www.designengineering.com/features/whale-ofan-idea
Yellow fin tuna Image: http://www.ausasiagroup.com/ PX_AATUNA/WTBF_Fish_Species.html
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Concept development
Concept development We wanted to create an initial first step towards an open source bionic AUV. To prototype it we focused mainly on the development of biomimetic kinematics and biomimetic physical form. We chose to work with servos for actuators. These make it easier to prototype the swimming motions than muscle wire would, but are noisy and would not be used in a final product. Because this particular prototype is not intended to dive to any great depths the camera and other electronics on board exist solely to create an engaging proof of concept that is able to swim autonomously in a controlled environment. For a fully seaworthy AUV we would need more work on programming so the AUTuna could navigate and perform a real dive.
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Tubercled hydrofoils(Bright colored)
Caudal keel
Tuna body shape Flat Window
Pectoral fins for vertical steering
Starting point
The shape of the fish is almost completely dictated by the research from the previous phase. It’s body has an elliptical cross section to resist the lateral forces of the tail fin and an overall shape inspired by the tuna rather than one of the very fastest swimmers such as the black marlin. This is because the marlin and its family of so called billfish have a much longer shape, which would make for a very cumbersome robot.
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Visability
The black color was chosen mostly because we like it, although it could have been any color as below a few hundred meters there is no light in which to see anyway. We made some of the fins yellow to improve visibility during launch and retrieval as a black object below the surface is nearly impossible to see. The yellow fins are also a nice reference to the yellowfin tuna.
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Tail fin movement
Water flow
Caudal keel
Tuna seen swimming from above.
Tubercled hydrofoils
The fins are tubercled hydrofoils to maximize the angle of attack and thereby thrust.
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Caudal Keel
The posterior tail joint has been given a caudal keel like that of a real tuna which helps stabilize flow and streamline the tail for stable lateral movement of the tail through the water.
Caudal keel
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Camera
LED package
Light sensors
Range finders
Head
The shape of the head is defined by the components it needs to carry. It is a hydrodynamic casing for a pressure resistant cylindrical housing for a camera, 4 rangefinders for obstacle avoidance each needing a flat transparent window and an LED array with light sensors to control lighting for the camera.
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Dorsal and Abdominal fin resists lateral force.
Pectoral and pelvic fins resist vertical force of the AUTuna’s slight buoyancy.
Positioning of fins
The positioning of the fins is driven by our experience from the earlier testing. The vertical fins are positioned centrally where the majority of the lateral deflection from the tail motion would occur without them. The Autuna is made to be slightly buoyant and use hydrodynamic downforce to keep it submerged. That way, if it runs out of battery or something else fails, it will simply float to the surface. The Autuna has two sets of horizontal fins. One articulated set near the front that vary their pitch to steer it up or down, and one stationary set to the rear for the front set to work against.
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Fin size
The size of the fins is a compromise. Ideally we want larger caudal and pectoral fins, and smaller dorsal and pelvic fins. But, we opted for the benefit of having them all be instances of the same fin in order to rationalize production by only requiring a single mold.
Electronics
The electronics are housed in a flexible oil bladder made from a common household item, a silicone sugar bread form from IKEA. The bladder is mounted against a flat membrane with standard cable glands for each cable required for the servos and the sensor module in the head. This setup is inherently pressure proof, as the flexible silicone will deform to allow any air bubbles inside to compress without straining the watertight seal. Another benefit, is that the need to waterproof the depth sensor module is removed as it can be contained within the oil that will always hold the same pressure as the outside water.
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The tailored fish skin folded up around the tail in spite of compensative cuts
A simple nylon stocking outperformed the sewn skin
Skin
The AUTuna is designed to be draped in a drag-reducing outer skin. This doesn’t need to be waterproof, it needs only to follow the form of the body underneath as closely as possible. At first we thought sewing a tailored suit was the best option. We made a prototype from a vinyl backed nylon textile, but it didn’t flex well enough, and was a very involved effort. So much so, that we thought it
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might discourage any future wouldbe AUTuna builders. We therefore opted for a simple nylon stocking. The stocking proved to outperform the tailored suit in terms of figure hugging and ability to flex with the movement of the robot. However, a suit with a zipper would make changing the battery and performing other service easier to do.
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Analyzing the swim pattern of a tuna we found on Youtube (https://www.youtube.com/ watch?v=mSYLXQcFWZM)
Modelling the thunniform swimming style
Because thunniform swimmers were shown to greatly outperform the rest, we decided to build a thunniform robot. Recreating the swimming style of a tuna was done by watching video of a tuna swimming, and writing a piece of software in Processing that allowed us to graphically experiment with changing body proportions, angular deflection of the joints and their phase offsets. We found that with four articulated joints, three for
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Interface for sketching swimming patterns made in Processing.
Porting the swim pattern to the servos.
the tail motion and one to control the pitch of the tail fin, we were able to fairly accurately recreate the thunniform swimming style. The length of the servo joints are based on findings done with visual comparison of a video of a tuna, to the graphical representation in the swimming style software.
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Linear servo sweep cycle
Sine wave servo sweep cycle
Improving the kinematics
At first we ran the code with linear back-and-forth motion, which looked very robotic. When we drove the deflections of each joint from a sine wave, we discovered that what makes movement look biological is smooth accelerations. The sinusoidal swim cycle brought the fish to life, with its movement looking graceful and effortless. Once the swimming style matched the tuna from the video, it was just a matter of deciding on the
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Programming the fish required resolution for the prototype’s swim cycle and extracting the angular values from the swim style software. To calibrate things, we were able to get the software to send the values to the microcontroller in real time. The code for our fish swimming style tool can be found on our Github repository for those who want to give it a try. Hydrobionics -> Autuna
Once the angular deflections and phase offset for each servo was determined, it was a simple matter to program what we refer to as the swim cycle of the Autuna. Each servo runs through a cycle of 360 steps, with values from a sine wave with its lower extreme at 0, and higher extreme at 360. The wave exists as a lookup table of values generated with an online digital sinewave generator.
This saves a lot of microcontroller processing power, when it can simply find the next servo value in a table rather than computing it for every step. The one we used can be found at http://www.meraman.com/htmls/ en/sinTableOld.html. The values from the sine wave are mapped to the angular deflections determined for each servo by the Processing tool.
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Code structure
The main loop of the Autuna program runs a check of all the sensors, before it determines where to angle the servos. First it checks the depth module and angles the pectoral fins to maintain the target depth. Second, it checks for obstacles with the optical range finders. If one or more of them report a reading within the threshold of 300 mm, the program offsets the servo positions to steer the robot away from whatever triggered the sensor. Third, it checks the ambient light levels to determine whether they are above or below the target
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level needed for the camera. If below it fades the LED array up. If above, it fades the LED array down. Finally, the program iterates the position in the swim cycle sine wave table, and adds any sensor driven offsets to the new servo positions. After writing the new positions to the servos, it repeats the process. The arduino code for the AUTuna can be found on Github along with the swimming form software.
Main loop Check sensors↘ Check depth, adjust heading↘ Check obstacle sensors, adjust heading ↘ Check Light, adjust light↘ Check sensors↘ Check depth, adjust heading↘ Check obstacle sensors, adjust heading ↘ Check Light, adjust light↘
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First tank swimming test
We were honestly quite surprised when the Autuna just worked on the first try in the water. It took its very first swim strokes with ease, although the tank walls were triggering its lateral rangefinders constantly causing it to twitch back and forth a little to avoid making contact.
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Buoyancy and balance
When first submerging the AUTuna, it was not surprisingly very buoyant as we had taken “you can always add lead� to heart. We added 530 grams of ballast, which we positioned carefully in order to balance the robot. This also means that the AUTuna has a payload capacity of 530 grams.
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Cold.
Open water swimming test
Confident that our fish worked, we went to a local beach for the first open water test. With enough space to maneuver, the AUTuna astonished us with how well it moved in the water. It looked completely effortless, something that can’t be rendered with a still picture and really must be seen in a video. Once back on land, we extracted the footage from the onboard camera which we found to be absolutely hypnotic.
Success!
Although it was just video from a mostly featureless sandy bottom, there was something very intriguing about how the camera moved. It oscillated slightly from side to as it glided through the water, looking like something out of a jaws movie. As the AUTuna currently has no positioning systems, Hans Jakob had to get into the water with it to keep it from swimming away.
Well.. The camera was placed slightly tilted. But, none the less, the footage was captivating
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Result
The result The AUTuna swims like a cross between a shark and a tuna. With relaxed strokes to the tail beat frequency of a shark in the swimming style of a tuna, it glides gracefully through the water with a cruise speed of about 1 meter/second.
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AUTUNA Open source Bionic AUV
Something to build on The AUTuna is an excellent starting point for the DIY community to develop further. We have done the hard work of defining fish kinematics and writing software to recreate them. And perhaps more importantly, shaped a machine with a form factor so unusual that it catches the attention of individuals otherwise not interested in subsea technology. The following pages outline how we envision a likely user scenario.
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Assemble
Following detailed video instructions online, the assembly of the AUTuna would be an enjoyable learning experience, not just a means to an end.
Order a kit
The AUTuna would be sold in much the same way as the OpenROV or any RC model, as a kit where the user does most of the assembly. Only the parts requiring precise or advanced machinery would come premade. Such as printed circuit boards, machined parts and other electronics. It is not a simple product, and as such requires the user to get well acquainted with it’s components and inner workings.
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AUTUNA Open source Bionic AUV
A highly portable AUV
Once the body is assembled, the fins are field detachable, allowing the AUTuna to fit nicely in a bag for ease of transportation to launch sites.
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Program its route
At the launch site the user would need only to attach the fins, and plan a mission on a smartphone app before launching the AUTuna into the water. The AUTuna will then autonomously carry out the mission defined by the user, before returning home.
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Motion triggered video recording
We propose that the AUTuna employ simple computer vision to determine whether or not the image has changed since the previous frame, and so detecting if there has been any movement, or if there is anything in frame at all. That way one will not have to sift through recordings with hours of black nothing, and the AUTuna can undertake longer dives with less required video storage space. An example of this technology is the open source Motion for linux, a software motion detector intended for security cameras1.
1 http://www.lavrsen.dk/ foswiki/bin/view/Motion/WebHome
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Share
Once the AUTuna has been retrieved the user extracts the footage and shares it online if anything of note was captured.
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AUTUNA Open source Bionic AUV
Available at:
Github.com/ Hydrobionics/Autuna Download the code and 3D models.
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Reflection Looking back on the project
The project started with a very wide scope. Our starting point was that we wanted to “explore what kind of contribution we as industrial designers could make to ocean science”, and we believed we would settle on a more user friendly sailing drone of some sort. In hindsight we find it a little baffling how it has morphed from there into a bionic autonomous underwater vehicle, or AUV for short. This is the first time either of us have ever taken on a project with a brief this vague, and running a project with such a wide scope has been very difficult. Not knowing what the result would be nor who the intended user was, made the research phase very unfocused as there was no clear way to assess whether something was relevant for the project or just very interesting. This caused the research phase to take very long, leaving little time for concept development. With that said, we can’t imagine having thought of the concept we landed on, were it not for the broad research we did. We didn’t know until late March that we were going to do a bionic AUV, and we find it baffling that we between then and May have designed and built a working underwater biomimetic robot. Our impression over the years has been that students at AHO usually settle for a few renderings and a physical model no more than a visual mockup. Although the project has been challenging, it has also been a valuable experience. Because the project targets the Do-It-Yourself community, the work would suffer a lack of credibility if we had not actually “done it ourselves”. We have gained extensive experience in the challenges facing an underwater electronics build such as waterproofing cable connections, or balancing buoyancy and center of gravity. We wouldn’t have had any of these insights if we didn’t actually make the robot. 118
Having done such a project is also valuable in and of itself, as we doubt we’ll ever have the opportunity to work so exploratively again.
Thoughts on our result
As outlined in our introduction, very little is known about the worlds oceans. It’s absurd to note how much we know about Mars and other planets, and how little we know about the oceans. The oceans are paramount to our existence, yet our species seems more fascinated by other planets than our earthly waters. However, when a video of an unusual animal from the ocean appears on youtube, it can go viral as seen earlier in our report with Edith Widder and her video capture of the giant squid. Netflix has no reason to care about anything else than what attracts viewers. The fact that they have several documentaries about oceans makes us believe that there is an interest there, but that it needs more material to flourish into something more than casual entertainment. We think that the more people who see video of new or beautiful or bizarre or otherwise exciting species, the more people will be able to relate to our oceans. As outlined early on in this report, amateur astronomers are providing a valuable service to the world’s professional astronomers. Although the amateurs have lower quality equipment, they are providing higher bandwidth with more eyes on the skies. Amateur astronomers are typically the first to discover new celestial bodies, and the professional community use their findings as a reference for where to point their telescopes. Democratizing access to equipment that can lower cameras deep into the water, would likely provide a lot of cameras in the water and could stand to provide the same for the deep ocean. Open ROV is providing this for shallow water and is creating quite a stir as seen in the New York Times (reference) article about them. If we could help provide a platform that can provide the same
for deep waters, the world would learn about the depths a lot faster. Therefore we firmly believe that the more cameras in the water, the better. Shaping the AUV as a fish, that moves like a real fish, will according to all our research provide numerous benefits both in terms of performance, and getting attention. It has certainly attracted the attention of our peers across classes at AHO. Although the AUTuna performed beautifully on it’s first open water trial, it would have been very interesting to have more time with it to explore other fin placements, different planforms and cross sections of the hydrofoils and variations of the kinematics. We did observe a slight lateral oscillation of the head which effectively means it’s dumping energy to the sides that should have been directed backwards. Another set of dorsal and abdominal fins would probably fix this.
hopes to crowdsource innovation of future military drone technology. ( ht t p: //di yd ro ne s .co m /p rof ile s / blogs/darpa-creating-its-own-diy). Looking at what has happened through open source technology in other industries such as 3D printing through the Reprap Project or airborne drones through DIY Drones, we believe that if the same were to happen for the ocean science community, the world might be a better place for it. We hope that our project could contribute to the much needed push that gets the ball rolling.
Open source technology has democratized other industries by bringing the costs down to a level that a hobbyist can afford. Prime examples are the Reprap Project & DIY Drones. The reprap project is an initiative to make a machine that is capable of completely replicating itself. (http:// reprap.org/wiki/RepRap) They are far from achieving it still, but along the way they have started a billion dollar industry, the consumer 3D printer market. Makerbot, Ultimaker and all the rest owe their existence to the Reprap project. More closely related to our project, the DIY Drones forum, is a forum where hobbyists share experiences from building and operating homemade aerial drones. (http://diydrones. com/) The US military’s Defense Advanced Research Projects Agency, DARPA was impressed enough by the collective knowledge of the DIY Drones community to launch their own derivative, the “UAV Forge” in 119
Hydrobionics Master thesis of Per-Johan Sandlund & Hans Jakob Føsker The Oslo School of Architecture and Design, Spring 2014
Students: Hans Jakob Føsker Per-Johan Sandlund
Supervisors: Steinar Killi Etienne Gernez
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