[Title will be auto-generated]

Smart Chips Project

Field Tests of RFID Technology for Construction Tool Management Texas A & M University Julian Kang, Ph.D Paul Woods, Ph. D. Jason Nam

FIATECH™ Charles R. Wood

June 30, 2005

Field Tests of RFID Technology for Construction Tool Management

i

Smart Chips Project These field tests were conducted as part of the FIATECH™ Smart Chips™ Project.

FIATECH is a member sponsored non-profit industry organization. Neither the Smart Chips Project, nor this report would not be possible without the support of FIATECH Smart Chips Project sponsor organizations. Anyone interested in the FIATECH Smart Chips Project should contact Charles Wood (cwood@fiatech.org , 713-523-5380) We wish to express our appreciation to the following companies for their support of the Smart Chips Project and many other FIATECH efforts: Aramco Service Company Bechtel Corporation ChevronTexaco E. I. duPont de Nemours & Co., Inc. Fluor Corp.

Intel Corporation Jacobs Engineering Kellogg, Brown & Root, Inc. Procter and Gamble Zachry Construction Corporation

Copyright ©, 2005 by FIATECH on behalf of contributing organizations. All Rights Reserved This report has been developed as a cooperative effort with input and support from the following contributing organizations: FIATECH, a non-profit joint-industry organization affiliated with the University of Texas

Zachry Construction Corporation Texas A&M University Houndware Corporation Contributing organizations may reproduce and distribute this work, at no cost; and are permitted to revise and adapt this work for internal use, provided an informational copy is furnished to FIATECH. FIATECH members may reproduce and distribute this work internally at no cost, and are permitted to revise and adapt this work for internal use, provided an informational copy is furnished to FIATECH.

This report is available to non- members by purchase; however, no copies may be made or distributed and no modifications made without prior written permission from FIATECH. To purchase this or other FIATECH publications, contact FIATECH at www.fiatech.org or 512-232-9600.

Field Tests of RFID Technology for Construction Tool Management

ii

Smart Chips Project

Acknowledgements The work described in this report would not have been possible without the contributions of a number of individuals. The authors would like to thank Tom Hannigan, Joanne Thomas, Todd Sutton, and Felix Perez of Zachry Construction Corporation for their time, support, and ideas in the planning and execution of the field tests. We are grateful to Dean Perry and Jeremy Zheng at Houndware Corporation, for the technology and technical expertise they supplied to this effort.

Field Tests of RFID Technology for Construction Tool Management

iii

Smart Chips Project Executive Summary This report presents the results of field tests conducted by the FIATECH Smart Chips Project in collaboration with Zachry Construction Corporation, Texas A&M University, and HOUNDware Corporation. The purpose of these tests was to investigate the technical feasibility of using RFID technology to automate tool management processes.

RFID technology offers the possibility that tools and valuable supplies tagged with RFID devices could be issued and received from central storage and the issue/receipt documented without intervention or help from a tool storage attendant. In addition, RFID tagged tools kept in distributed field storage boxes could be automatically inventoried in realtime on demand. Such automated systems have the potential to: 1) reduce theft, 2) optimize tool inventories, 3) insure that crafts have access to the appropriate tools as needed, and 4) reduce overhead labor cost of managing tools.

The objective of these tests was to investigate the reliability and efficiency of RFIDbased tool management applications against barcode or other processes. The potential automation of two specific tool management processes was addressed in these tests: 1) Toolroom issue and receipt (The Portal Test), and 2) On-site tool inventories (The Gangbox Test). In addition data was gathered and analyzed to determine the relative efficiency of manual tool identification using RFID vs bar-coding (The Tool Identification Time Test).

Specifically the investigations were designed to answer the followings questions: • Is it technically feasible to automate tool room issue and receipt (i.e. reliably record issue and return of tools without human intervention) - the Portal Test?

• Is it technically feasible to automate real-time inventories of tools in field storagethe Gangbox test?

• Would RFID technology speed up manual tool identification processes vs barcoding system- the Tool Identification Time test?

The tests provided empirical evidence to support the merit of RFID technology in tool management. The prototype RFID system worked reliably in all of the tests. The result of the Gangbox Test indicated that RFID technology is reliable in inventorying tools in field storage.

The result of the Portal Test indicated that the RFID portal is capable of automating tool issue and receipt. It appears that those technical issues encountered during the tests (e.g. occasional missed tags) could be resolved with relatively little additional system development.

It should be noted that while the tests reported here were encouraging with respect to the technical potential of RFID in tool management, the researchers did not attempt to quantify economic cost or benefit of a commercial application. The economic feasibility of such an application would depend on a number of factors such as: 1) specific beneficial impact to a particular organization 2) cost of the technology, and 3) cost of implementation (e.g. training, system integration, etc.).

Field Tests of RFID Technology for Construction Tool Management

iv

Smart Chips Project

Table of Contents 1. Introduction .......................................................................................................................... 2 1.1 Potential of RFID Technology for Tool Management ..................................................... 2 1.2 RFID Background ............................................................................................................ 3 1.3 Objective and Description of Field Tests ......................................................................... 4 2. Current Tool Management Processes and Proposed Changes......................................... 8 2.1 Current Processes............................................................................................................. 8 2.2 Technology Enabled Process.......................................................................................... 10 3. RFID Technology................................................................................................................ 12 3.1 RFID System Selected for the Tests............................................................................... 12 3.1.2 Readers (Controller, Receiver) and Activator (Exciter).......................................... 13 3.1.1 Active vs. Passive Systems ..................................................................................... 14 3.2 RFID Portal Configuration............................................................................................. 15 3.3 Gangbox Configuration.................................................................................................. 16 4. Field Test Implementation................................................................................................. 18 4.1 The Portal Test ............................................................................................................... 18 4.1.1 Experimental Setup ................................................................................................. 18 4.1.2 Methodology ........................................................................................................... 22 4.1.3 Results and Interpretations...................................................................................... 25 4.2 The Gangbox Test .......................................................................................................... 26 4.2.1 Experimental Setup ................................................................................................. 26 4.2.2 Methodology ........................................................................................................... 27 4.2.3 Results and Interpretations...................................................................................... 30 4.3 The Tool Identification Time Test .................................................................................. 31 4.3.1 Experimental Setup ................................................................................................. 31 4.3.2 Methodology ........................................................................................................... 31 4.3.3 Results and Interpretations...................................................................................... 32 5. Conclusions ......................................................................................................................... 36 Appendix A - Statistical Comparison of RFID vs Barcode Based Tool Tracking Process .................................................................................................................................................. 39

Field Tests of RFID Technology for Construction Tool Management

v

Smart Chips Project 1. Introduction This report presents the results of field tests conducted by the FIATECH Smart Chips Project in collaboration with Zachry Construction Corporation, Texas A&M University, and HOUNDware Corporation. The purpose of these field tests was to investigate the technical feasibility of using RFID technology to effectively automate tool management processes.

Radio Frequency Identification (RFID) technologies provide a wireless means of communication between objects and the systems we use to manage them. RFID has the ability to identify and track specific physical assets in real-time without human intervention or lineof-sight access to the object. There are many potential applications of this technology. Retail, consumer products, transportation, agriculture, manufacturing, and other industries have been using radio frequency technology for years.

1.1 Potential of RFID Technology for Tool Management Recent research addressing the advantage of Radio Frequency Identification (RFID) technology over the barcode system and the trend of manufacturing, logistics, and retail industries in utilizing RFID technology have drawn attention in the construction industry.

Recent research conducted in conjunction with FIATECH Smart Chip Project concluded that RFID technology has the potential to both improve the efficiency and the accuracy of current material tracking processes, and eventually could enable a more complete automation of these processes.

FIATECH Smart Chips Project member companies, including Zachry Construction, had been considering possible application of RFID to site tool management for over a year prior to these trials. Most of these companies, including Zachry, have used barcode based tool tracking systems to expedite the tool issue and receipt process and eliminate manual data entry. Although the barcode based tool tracking systems were an improvement over manual tool system data entry, the barcode process is still subject to some error and requires a dedicated room attendant for issue and receipt. Tool management is an area where the

Field Tests of RFID Technology for Construction Tool Management

-2-

Smart Chips Project construction industry may benefit from RFID technology. Specifically, the error free tool identification and process automation enabled by an RFID system could: a) Improve tool utilization (i.e. the time tools are actually used) and reduce idle tool inventories. b) Improve craft productivity by insuring that appropriate tools were available to crafts. c) Reduce tool and supply loss (shrinkage), by improving accountability. d) Reduce overhead labor and human error in managing tools and supplies

1.2 RFID Background The fundamental parts of an RFID system include: 1) a transponder, usually referred to as a tag, and 2) an interrogator, usually called a “reader”. Tags are attached to the physical object being tracked. Readers may be fixed or mobile and are able to communicate data to and from the tags. The reader may also exchange data with the larger information systems they support. Data is exchanged between tags and readers using radio waves. Each RFID tag contains a unique identifying number. Some kinds of tags can store and transmit other information relevant to the object they are tracking. In more sophisticated applications, tags can incorporate sensors, data storage and even processors that enable them to collect store, and interpret additional information (e.g. temperature, location, etc.) about the object.

In a typical RFID system, the reader prompts the tag for its data, or processes the signal being broadcast by the tag, decodes the transmission and transfers the data to a computer. The computer, in turn, may simply record the reading, or look up the tag ID in a database to direct further action. They system may also direct the reader to write additional information to the tag.

The current generation of RFID allows many tags to be read at the same time. This ability to identify multiple objects in a short time supports high-speed real-time object identification for material handling applications. Because no line of sight is required between the reader and the tag, unattended reading stations can be set up to identify objects regardless of their orientation to the reader (i.e. in random or ‘chaotic’ processes). Fast simultaneous

Field Tests of RFID Technology for Construction Tool Management

-3-

Smart Chips Project processing, automatic unattended reading (and the reduction of potential human error), data security (can’t be copied) and the ability (in some tag systems) to store and process information locally with the object (as opposed to a remote database) are the main performance characteristics that set RFID apart from bar code.

Because Radio Frequency Identification (RFID) technology can identify multiple objects at once without human intervention or line-of-sight access, it is replacing barcode systems in many industry applications. A white paper produced by the Construction Industry Institute (CII) in 2002 proposed that RFID technology would improve the material handling process by eliminating manual data entry and by facilitating automated solutions. Recent research conducted in conjunction with FIATECH Smart Chips Project tested the reliability of RFID technology in tracking uniquely tagged construction materials and equipment, and concluded that RFID technology has the potential to improve both the efficiency and the accuracy of current material tracking processes, and eventually could enable a more complete automation of these processes (Song et al. 2004).

1.3 Objective and Description of Field Tests The key issue to be investigated in the field test is the RFID technology’s reliability and efficiency in tool tracking. Tools on a typical construction project are issued and returned to and from a central manned room and issued tools are stored temporarily in a field gangbox on the jobsite. Therefore, the researchers chose to test RFID technology for the process of 1) checking tools out of the tool room and returning tools back to the tool center and 2) identifying tools sitting in the gangbox. The goals of the field tests were: 1. To determine the reliability of RFID technology in automatically identifying tools passing through a tool room portal for checking in and out. (The Portal Test) 2. To determine the reliability of RFID technology in identifying tools in field storage boxes. (The Gangbox Test) 3. To measure the time saving one can make in the process of checking tools in and out by utilizing RFID technology. (The Tool Identification Time Test)

Field Tests of RFID Technology for Construction Tool Management

-4-

Smart Chips Project

The Portal Test - The researchers assumed that one of the best ways of utilizing RFID technology in the issue/receipt process was to have the craft tool users pass in and out of the tool room through a portal armed with RFID readers. If the RFID portal can identify multiple tools passing, associate them with a worker, and record them in the tool tracking system automatically as they pass in or out of a tool storage room, it would be possible to eliminate paper documentation or manual computer input, and eventually automate the entire tool issue/receipt process. This test was intended to address the following questions: 1. Can the RFID reader reliably identify multiple tags passing the portal at the same time?

2. Would the RFID portal based tool tracking process be faster than existing tool tracking processes (e.g. the barcode based tool tracking process)?

In order to seek answers for these questions, “The Portal Test” was prepared and conducted. For this test, a portal was fabricated and armed with RFID technology for tool identification. Two identical sets of 7 different tools were then selected and one set of tools had RFID tags attached. Two checkpoints were designated in the Zachry Construction’s tool center in San Antonio, Texas and two routes connecting these checkpoints were drawn. The length of the two routes was identical. In the middle of one route, a barcode based tool checking counter was set up. One crew was recruited as tool counter clerk. On the other route, the RFID portal was installed. Another two workers were recruited and asked to move tools from one checkpoint to another through either the barcode based tool counter or the RFID portal. Elapsed time needed for hauling tools between two checkpoints back and forth was measured and compared.

The Gangbox Test - The researchers also speculated that identification of tools in the field gangbox using RFID technology would improve overall tool management by reducing underutilized tools. One concern in applying RFID technology to identify tools in the gangbox was interference of the RF signal by metal or liquid material. The RFID tags

Field Tests of RFID Technology for Construction Tool Management

-5-

Smart Chips Project attached on metal tools may not be detected because of metal interference. Another concern was the location of tags on the tool. If the RFID tag was attached on the deep corner of the tool, the travel of the RF signal could be hindered. One may therefore wonder if the RFID reader would identify all tools sitting in the gangbox reliably regardless of metal interference and tag congestion.

“The Gangbox Test” was designed to determine how reliably the RFID reader detects the RFID tags attached to the tools in the gangbox. Expecting that the travel of the RF signal may be hindered by metal, researchers speculated that the RFID tags may not be reliably detected if various tools (made of metal) are piled up in the gangbox.

To verify the

researchers’ theory, an experiment similar to a hide and seek game was prepared. For this experiment, twelve tools were selected and RFID tags were attached to these tools. Groups of other tools were also brought to the gangbox. Three workers recruited for the test were instructed to pile up these tools with or without RFID tags in the gangbox. While piling up tools, they were specifically instructed to cover up the RFID tags with any tools that would hinder the RF signal from traveling to the reader. Once they finished piling up tools, the research ran the RFID reader installed in the gangbox and counted the number of tags that the reader identified within 2 minutes. The workers then rearranged the tools again for another round. This experiment was conducted 30 times.

The Tool Identification Time Test - Another concern the researchers had in identifying tools in the gangbox using RFID technology was tool identification time. How fast the RFID reader would identify all tools sitting in the gangbox? Would RFID technology speed up manual tool identification processes against the bar-coding system? In order to seek the answer for this question, “The Tool Identification Time Test” was designed. For this test, nine tools were randomly selected as a set and had RFID tags attached. The gang box was be fitted with an active RF tag reader. The reader was attached to electrical power and the computer network. A second set of nine similar tools was placed on a counter. A bar code reader was setup to scan the tools. One crew was recruited and instructed to scan all nine tools in either

Field Tests of RFID Technology for Construction Tool Management

-6-

Smart Chips Project the RF Tag set or the Bar Code set. The elapsed time of each observation was recorded. The observer also recorded the number of tools correctly identified by location within the gang box.

Field Tests of RFID Technology for Construction Tool Management

-7-

Smart Chips Project 2. Current Tool Management Processes and Proposed Changes 2.1 Current Processes The principal control process for tool management on a construction site is the issue and receipt of tools from and back into a central tool storage area (tool room). The second important process supporting management of tools and valuable supplies is to conduct periodic inventories of tools and supplies issued in the field, as well as those remaining in the tool room.

The objectives of these tool management processes are to: 1) insure that

appropriate types and quantities are available when needed by crafts, 2) manage inventories to insure that tools and supplies are used productively and not idle for unreasonable periods of time, and 3) reduce loss or theft of tools and supplies by assigning worker responsibility to specific items.

Currently, tool management systems rely on manual identification or barcodes to identify tools when they are issued, received, or inventoried at the tool room. Whenever workers need a new tool, they are supposed to go to the tool counter and tell the tool room attendant what they need. The tool room attendant then locates the requested tool, and records the tool ID and employee ID in the Tool Management System (TMS). Once this information is entered into the TMS, the tool is released to the craft.

After issue from the tool room, tools and supplies are usually stored in boxes (cribs), which are distributed at convenient locations around the construction site. Cribs give craft workers easy and timely access to the tools they need without having to go back and forth to a manned tool room each time a tool is needed. Typically, each crib is assigned to a specific crew. In theory, tools kept in a given crib are the responsibility of the leader of the crew using the crib, and the crew leader controls access to the crib. In practice, access to the cribs is not controlled during work hours, because crew leaders want workers to have timely access to the tools they need and cannot stop work to open a crib and issue or receive tools.

Field Tests of RFID Technology for Construction Tool Management

-8-

Smart Chips Project Occasionally, during the course of a project, inventories may be taken to account for the tools stored in the cribs. These inventories may be prompted by recognition of shortages of particular tools, or to free up unused tools to be sent to other area or projects.

Tool Issue/Receipt Process - Currently Zachry Construction is utilizing the barcode based Tool Tracking System (TTS) for managing tool tracking. Whenever workers need a new tool, they are supposed to go to the tool counter and tell the tool room attendant what they need. The tool room attendant then locates the tool requested, brings it back to the counter, and puts the tool ID and employee ID in the TTS. Once this information is issued in the TTS, then the crew can start using that tool. Figure 2-1 represents this process.

If RFID technology is applied to the current TTS, several steps in tool room issue and receipt can be eliminated. Workers who need a tool could locate it in the tool room by themselves without the tool room attendant. When they pass the portal, the tool ID and employee ID should be scanned by the RFID reader and entered in the TTS. As shown in Figure 2-1, no tool room attendant would be needed if RFID technology is applied to the current TTS. In addition, the process of checking tools in and out may be accomplished faster.

Requestor

Requestor

Requestor

Tool Room Attendant

Tool Room Attendant

Tool Room Attendant

Tool Room Attendant

Requestor

ID Need for Tools

Go to Tool Room

Request Tools from Attendant

Locate & Pull Tools

Pull up Employee in TTS

Enter Tool No./Qtys

Process Issue

Take Tools

Current process Requestor

Requestor

Requestor

Requestor

Requestor

ID Need for Tools

Go to Tool Room

Locate & Pull Tools

Enter Tool No./Qtys

Take Tools

Changed process with active tags Fig 2-1) Tool Check-in/out Process Improvement by RFID Technology

Tool Inventory Process - From time to time in the course of a construction project it is necessary to take inventories of construction tools belonging to the contractor or owner, both those tools remaining (unissued) in the tool room and those in field use or storage. These

Field Tests of RFID Technology for Construction Tool Management

-9-

Smart Chips Project inventories may be made in order to account for specific tools needed for completion of particular phases of the work (e.g. recovering concrete placement tools and equipment at the completion of concrete work) or to insure sufficient tools are available to begin work on new phases of a project. Occasionally, inventories may be taken so that workers are accountable for the tools in their care, and to discourage loss or theft of valuable tools. Sometimes tool inventories are necessary for asset accounting purposes.

These inventories are labor intensive, time consuming, and error prone. Typically, workers will take paper inventory lists into the field and check off those tools they find. An accurate inventory of specific tools requires that the worker clearly identify each tool he or she finds. Identification is based on reading an ID number marked or etched onto the tool.

Where barcodes are used and in good condition, the specific ID can be positively and accurately recorded with a handheld reader. This process is also subject to error, since a tool must be located (often in a storage box with many other tools) before it can be recorded, there is a good chance that tools will be missed. In addition, those tools that are found may be easily misidentified or incorrectly recorded, even in barcode systems where the barcode is subject to marking or damage in the course of construction work.

2.2 Technology Enabled Process RFID technology opens the possibility that tools and valuable supplies tagged with RFID devices could be issued and received from storage by craft workers, and the issue/receipt documentation process can be accomplished without the intervention or help from a tool storage attendant. RFID tagged tools issued from central storage and kept in distributed field storage boxes could be automatically inventoried as required.

For automated tool issue and receipt, workers with RF or ‘smart card’ identification would be able to enter a secure, unmanned tool storage area though a portal system designed to read the worker ID and permit access to pre-authorized workers. After the worker selects the necessary tool(s), he would carry the tools through the portal system exit, and the system would automatically record his exit and the ID(s) of the tools he is carrying. The transaction

Field Tests of RFID Technology for Construction Tool Management

-10-

Smart Chips Project is automatically recorded in the tool management system. The same process would be done in reverse as tools are returned to the central storage area.

For automated inventory of tools kept in site storage boxes, an RFID reader in the box would be prompted to read all of the tags inside the box. The list of tool IDs collected by the reader is then wirelessly communicated to the tool management system.

The tool

management system could then be inquired as to the tools that were not being used (i.e. rarely or never removed from the boxes) or tools that were not in the boxes when they should have been (e.g. at the end of a crew’s shift).

These automated systems reduce overhead labor and human error in managing tools and supplies. Craft productivity is increased by insuring that the appropriate tool is available and idle tools are identified and removed from the location. Most significantly, real-time inventory of tools on site can help better manage tool inventory by 1) reducing opportunities for theft, 2) identifying tools that are not used so they can be retrieved and used elsewhere, and 3) insuring that crafts have access to the appropriate tools called for in their work plans.

Field Tests of RFID Technology for Construction Tool Management

-11-

Smart Chips Project 3. RFID Technology 3.1 RFID System Selected for the Tests The prototype RFID system used in the test was supplied by eXI Wireless in Richmond, British Columbia. eXI is the parent company of Houndware Corporation, which supplied the tool management software for the tests. The RFID tool tracking system was selected based on the following considerations: 1. Signal read distances: Although a long distance RFID product was not required for tool tracking, RFID products that allow adjusting the distance range were considered to control the area where RFID tags are detected.

2. Size of tags: Expecting that RFID tags would be attached to small tools as well, the size of RFID tags was considered.

3. Suitability for existing tool tracking system: Zachry Construction was already using HOUNDware’s tool tracking system. RFID products that would best fit the existing tool tracking system were considered.

While the eXI and Houndware systems seemed appropriate for this test, neither the authors nor Zachry Construction Corporation endorse these systems over others that may be functionally similar.

3.1.1 RFID Tags For the field test, the active tags provided by eXI were selected (Fig 3-1). The size of the tag is 1.9” by 0.95” by 0.35” (4.8cm by 2.4cm by 0.9cm) and its weight is 0.46 oz (13g).

These tags were set in the test to transmit the RF signal every minute, and its frequency is 433.92 MHz. The active tag can be awakened and transmit the RF signal in response to the RF signal emitted from the activator (or exciter).

Field Tests of RFID Technology for Construction Tool Management

-12-

Smart Chips Project

Fig 3-1) RFID Active tag

Location of the tag on the tool was another issue discussed by researchers.

Suggestions made for the proper tag location included: 1. On the tool cover: It was considered as a convenient location for attaching tags.

However, tags could be harmed if multiple tools are piled up and tags are touched by other tools.

2. Inside the tool cover: Although tags installed inside the tool cover should be protected from getting broken by colliding against other tools, it was pointed out that installation of any electrical device inside the tool cover was prohibited by the OHSA regulation.

3. On the electric wire: It was considered as a good place to compensate abovementioned drawbacks. However, tags selected for our test were not small enough to be attached on the wire.

3.1.2 Readers (Controller, Receiver) and Activator (Exciter) The controller is the heart of the local perimeter system. The controller supports two distinct alarm conditions: Tag In Field (TIF) and Tag Initiated Communications (TIC). A TIF alarm is generated when a periodic RF signal of a tag is detected within the controller’s detecting boundary. A TIC alarm is generated when the RF signal of a tag awakened by the activator (or exciter) is detected within the controller’s detecting boundary. The R3 Controller, product of eXI was selected for the field test.

The receiver is a compact, unobtrusive device usually mounted out of the line-of-sight in areas such as drop ceilings. An eLink Receiver, also product of eXI, was selected for the field test. The eLink Receiver can be tuned to detect a tag’s RF signals within a 20 ft radius (approximately 1,000 ~ 1,500 sq.ft. coverage area).

Field Tests of RFID Technology for Construction Tool Management

-13-

Smart Chips Project The activator (exciter antenna) creates an electromagnetic exciter field that activates tags upon entry. The exciter field radiation patterns and size are dependent on the environment and can be adjusted from a few feet to 20 feet or more in a free space. The SRA Exciter Antenna utilized in the filed test is tuned to 307 KHz. It is fed and regulated from the controller. Hence, the combinations of the R3 Controller and the SRA Exciter Antenna were utilized for the field test.

R3 Controller

eLink Receiver

SRA Exciter Antenna

Fig 3-2) RFID readers and activator

3.1.1 Active vs. Passive Systems There were two fundamental types of RFID tags considered for the test: Active Tags and Passive Tags. Active tags are equipped with the battery and they can transmit the RF signal periodically by themselves as far as 300 ft without depending on any external power sources. The active tag’s operational life depends on the battery life.

Most current

commercial active RFID employ tags with an expected life of approximately 5 years. Passive tags do not require a battery. Instead they gain the power needed for transmitting the RF signal from the RF energy emitted by the reader. More powerful readers are therefore needed for passive tags. Since passive tags do not use the internal battery for operation, they can be

Field Tests of RFID Technology for Construction Tool Management

-14-

Smart Chips Project produced less expensively and their operational life cycle is normally longer than that of active tags. Table 3-1 presents pros and cons of RFID tags.

Table 3-1) Comparison between active and passive tags Active Tags Passive Tags Advantages Disadvantages Advantages Longer read range Greater tag size Lighter tags; can be (1-300 ft.)

(10g - several kg) very small Tags can be readGreater tag cost Less expensive tags write with onboard ($25-50) ($1-3, but some submemory $1 tags becoming available)

Can connect to sensors (i.e. tag tamper, temperature, on/off)

Battery-dependent operational life (6 months-5 years); some tags have replaceable batteries Heavier

Long operational life (3-10 years)

Can be in simple label form or even printed (requiring special ink)

Disadvantages Shorter read ranges (1-10 ft.)

Requires a higher powered reader ($1000-3000); portable readers require frequent recharging Most read-only

Tag is entirely inactive unless within proximity to reader (energy source) Source: www.exi.com

3.2 RFID Portal Configuration The prototype RFID portal used in these tests is composed of four motion sensors, one SRA exciter antenna, one R3 controller, and data processing software as shown in Figure 3-3.

The process of the RFID portal’s detecting the RFID signal and manipulating its corresponding data is: 1) The motion sensors detect the crew’s movement as he/she enters into the RFID portal.

2) Receiving the signal from the motion sensors, the R3 controller generates the RF signal of 307 kHz and emits it through the SRA Exciter Antenna to wake up active tags.

3) Awakened by the RF signal transmitted from the SRA Exciter Antenna, active tags emit the RFID signals of 433.92 MHz.

Field Tests of RFID Technology for Construction Tool Management

-15-

Smart Chips Project 4) The R3 controller detects the RFID signals transmitted from active tags and sends the tag IDs to the data processing system.

5) The data processing system retrieves tool information associated with these tag IDs from the database and presents it on the display.

Data Processing System

SRA Exciter Antenna

R3 Controller Motion Sensors Fig 3-3) RFID Portal System

3.3 Gangbox Configuration The RFID receiver (eLink Receiver) was installed in the gangbox. The RFID receiver is connected to an RFID signal monitoring application via the LAN cable. (see figure 3-4) The process of detecting the RFID tags inside the gangbox is: 1) The active tags attached on the tools transmit the RF signal every minute.

2) The eLink Receiver detects each RF signal from the active tags and sends the tag IDs to the monitoring application.

3) The RFID signal monitoring application searches tools in the database using tag IDs transmitted from the eLink and displays their information on the display.

Field Tests of RFID Technology for Construction Tool Management

-16-

Smart Chips Project

Gangbox

eLink Receiver

RFID signal monitoring application

Fig 3-4) Gangbox (RFID tool tracking system)

Field Tests of RFID Technology for Construction Tool Management

-17-

Smart Chips Project 4. Field Test Implementation The objective of the field tests was to investigate the reliability and efficiency of the RFID-based tool tracking process against the barcode or other processes. Three sets of field tests were collected in order to answer the followings questions: •

Is it technically feasible to automate tool room issue and receipt (i.e. reliably record issues and returns of tools without human intervention); and would RFID technology speed up manual tool identification processes vs a barcoding system - the Portal Test?

•

Is it technically feasible to automate real-time inventories of tools in field storage- the Gangbox test?

4.1 The Portal Test The portal test was designed to determine whether: 1) the RFID technology would reliably identify tools passing in each direction of the portal, and 2) whether the RFID/portal system identified tools faster than using a bar code system.

4.1.1 Experimental Setup The portal was set up to simulate conditions in a field tool center such that workers carrying tools out of the center through the portal would be recognized as having been issued those tools.

1. Two identical groups of 7 different tools (a total of 14 tools) were selected. Each group of tools was composed of 3 small-size tools, 3 medium-size tools, and 1 tool kept in the tool box. One group of tools had the RFID tags attached and designated as Group R. The other group of tools got the barcodes attached and designated as Group B. Seven tools in a both groups were again divided into three sub-groups such as smallsize tool groups (3 tools), medium-size tool group (3 tools), and tool in the tool case group (1 tool) in order to investigate whether the tool size or tool case would affect the tool tracking process (Figure 4-10).

Field Tests of RFID Technology for Construction Tool Management

-18-

Smart Chips Project 2. Each tool in Group R was designated as R1 to R7 (R1 to R3 for small-size tools, R4 to R6 for medium-size tools, and R7 for the tool in the tool case). Tools in Group B were assigned by the same numbering system that starts with B, so that R1 and B1 are the same tools.

3. Two gangboxes (Box A and Box B) were placed in the tool center as checkpoints (Figure 4-1). Two routes (Route R and Route B) were then drawn between these two gangboxes to simulate the process of checking tools in and out (Figure 4-2). The RFID portal placed in the middle of Route R (Figure 4-3). A simple tool checking counter was placed in the middle of Route B (Figure 4-4). One worker, who knew how to use the barcode reader, was recruited as tool counter clerk. He was instructed to scan the barcode on each tool as quickly as possible once it arrived at the tool checking counter.

Figure 4-1) Gangboxes (Box A and Box B)

Field Tests of RFID Technology for Construction Tool Management

-19-

Smart Chips Project 12ft

12ft Checkpoint B

27ft

Barcode Checking Counter

RFID Portal

Route B 12ft

Checkpoint A

Route R 12ft

Figure 4-2) Configuration of the RFID portal test

Field Tests of RFID Technology for Construction Tool Management

-20-

Smart Chips Project

a) View from the check in side (Box A to B)

b) View from the check out side (Box B to A)

Figure 4-3) RFID portal

Figure 4-4) Barcode checking counter

Field Tests of RFID Technology for Construction Tool Management

-21-

Smart Chips Project 4.1.2 Methodology Two workers (A and B) were asked to take a designated route (Route R or Route B) and move the tools between the Box A to the Box B back and forth. One worker was asked to take the Route R and go through the RFID portal when he was moving the tool with the RFID tag attached. While one crew was transporting the tools through the Route R, the other worker was asked to transport the tools with the barcode attached through the Route B. He was instructed to stop by the tool checking counter in the middle of the Route B and get the barcode of the tool scanned by the barcode reader. Elapsed times spent for moving tools between the two gangboxes were measured.

In order to investigate whether the number of tools checked in and out would affect the tool tracking process, the workers were asked to move 1) one tool at a time, 2) three tools at a time, and 3) five tools at a time. The workers were instructed to carry up to 3 tools with their bare hands. They, however, used a metallic wheelbarrow to move 5 tools.

A total of 30 measurements were collected for each test (with one tool, three tools, and five tools). The crew’s roles were switched in the middle of each test, as not to bias the result due to one crew’s superiority over the other crew in implementing the given task.

Moving one tool at a time 1. The Crew A and B were asked to pick up the tool R1 and B1 respectively from Box A. Both workers were asked to wait right next to the Box A for the next instruction.

2. Both workers were instructed to start moving the tool to the Box B at the same time.

Crew A was asked to take the Route R. Crew B was asked to take the Route B. Measurement for the elapsed time started.

3. Crew A was asked to go through the RFID portal (Figure 4-5). The crew was instructed to wait in the portal for about two seconds in order to get all tools identified by the reader. The crew then resumed moving the tool to Box B through Route R. The elapsed time was measured when the crew finished moving the tool.

Field Tests of RFID Technology for Construction Tool Management

-22-

Smart Chips Project 4. Crew B was asked to stop by the tool checking counter in the middle of Route B and get the barcode of the tool B1 scanned by the tool counter clerk (Figure 4-6). After the barcode was scanned, Crew B resumed moving the tool through Route B. The elapsed time was measured when the crew finished moving the tool.

5. Both workers were asked to come back to Box A and repeat the previous process to move remaining tools (R2 to R7 and B2 to B7) from Box A to Box B. 6. Once all seven tools were moved from Box A to Box B, the same process was repeated to get these tools transported back to Box A from Box B. The elapsed time for each and every transportation was measured.

7. After the process of moving tools between Box A and B back and forth was repeated for five times, the role of two workers were switched. Now, Crew A was supposed to take the Route B and move the tool with the barcode attached, and the Crew B was supposed to move the tool R1 to R7 to the Box B. 8. The same process was repeated for another five times after the workers’ role were switched. The elapsed time for each and every transportation was measured.

Moving three tools at a time 1. Two groups of 3 different tools (a total of 6 tools) were formed. Both groups are composed of one small size tool (R1 or B1) and two medium size tools (R4, R5 or B4, B5).

2. Both workers were asked to move these tools between Box A and B back and forth with the same rule employed for moving one tool at a time.

3. After both workers made 15 round trips, their role was switched. Both workers were asked to make another 15 round trips. For each and every trip, elapsed time for moving tools from one box to another was measured.

Moving five tools at a time 1. Two groups of 5 different tools (a total of 10 tools) were formed. Both groups consisted of two small size tools (R1, R2 or B1, B2), two medium size tools (R4, R5 or B4, B5), and one tool kept in the tool box (R7 or B7) respectively.

Field Tests of RFID Technology for Construction Tool Management

-23-

Smart Chips Project 2. Both workers were asked to move these tools between Box A and B back and forth with the same rule employed for moving one tool at a time.

3. After both workers made 15 round trips, their roles were switched. Both workers were asked to make another 15 round trips. For each and every trip, elapsed time for moving tools from one box to another was measured.

a) Moving one tool

b) Moving three tools

c) Moving five tools

Figure 4-5) Scanning the RFID tags in the RFID portal

a) Moving one tool

b) Moving three tools

c) Moving five tools

Figure 4-6) Reading the barcodes

Figure 4-7) Completion Signal

Field Tests of RFID Technology for Construction Tool Management

-24-

Smart Chips Project 4.1.3 Results and Interpretations Five different sets of data were collected in the portal test as presented in Table 4-1: 1. Elapsed time to move a small size tool between two gangboxes 2. Elapsed time to move a medium size tool between two gangboxes 3. Elapsed time to move a tool kept in the tool case between two gangboxes.

4. Elapsed time to move three tools at once between two gangboxes 5. Elapsed time to move five tools at once between two gangboxes.

Table 4-1) Elapsed time to move tools between two gangboxes (Seconds) Categories Small-size Tool Medium-size Tool Tool in the Tool Case Three Tools Five Tools

RFID Group 24.10 24.60 24.10 23.50 26.97

Barcode Group 26.22 26.67 34.10 43.60 51.10

Comparison with One Small-Size Tool The difference of population means between the RFID group and the Barcode group was 2.12 seconds. The measurement of each group does not satisfy normality requirements.

The Wilcoxon rank sum test, therefore, was employed to test whether there is any statistically significantly difference between two groups’ measurements. The resulting p-value (0.014) of the test indicates that tools in the RFID group were transported faster than those in the barcode group.

Comparison with One Medium-Size Tool The Wilcoxon rank sum test was employed again. The resulting p-value, 0.003 of this test indicates that the population mean of the RFID group is not equal to that of the barcode group. The box plot further indicates that the elapsed time for moving three tools at once with the RFID based tool tracking process is less then that of the barcode based tool tracking process.

Comparison with one tool kept in the tool case

Field Tests of RFID Technology for Construction Tool Management

-25-

Smart Chips Project The difference between sample means is distinctively 10.10 seconds. Since the sample sizes are small, we employed the Wilcoxon rank sum test although both measurements satisfy the normality issue. The p-value of the test marked 0.000, which indicates a distinctive difference between two groups. It is reasonable to determine that the elapsed time of the RFID group was significantly less than that of the barcode group.

Comparison with three tools- The normality test indicates that the Wilcoxon rank sum test should be employed. The resulting p-value of the test, which is 0.000, indicates that the null hypothesis should be rejected. It is safe, therefore, to conclude that the population mean of the RFID group is not equal to that of the barcode group. In fact, the box plot shows that the elapsed time of the RFID group is less than that of the barcode group.

Comparison with five tools - The difference between two sample means is 24.13 seconds. The p-value of the Wilcoxon rank sum test, which is 0.000, indicates that the null hypothesis should be rejected. It is reasonable, therefore, to conclude that the population mean of the RFID group is less than that of the barcode group.

4.2 The Gangbox Test The gangbox test was designed to figure out how reliably the tools with the RFID tag attached would be identified in the gangbox especially when the gangbox is filled with metallic tools.

4.2.1 Experimental Setup The Gangbox Test was designed to determine how reliably the RFID reader detects the RFID tags when tools are stored randomly in a congested gangbox. The experiment was set up as follows: 1. A gangbox was placed in the Zachry Construction’s tool center as shown in Figure 4-8 and the eLink Receiver was installed in the gangbox. The eLink Receiver then was

Field Tests of RFID Technology for Construction Tool Management

-26-

Smart Chips Project connected to the RFID signal monitoring application provided by HOUNDware as shown in Figure 4-9.

2. Seven different tools were selected and RFID tags were attached to these tools as shown in Figure 4-10. The RFID tags were set up then to emit the electronic signal every minute. With this setup, the eLink Receiver is supposed to detect all RFID tags within two minutes.

4.2.2 Methodology 1. Three workers were recruited and asked to load tools into the gangbox as shown in Figure 4-11. Among the tools they piled up, only 7 tools had the RFID tag attached.

The workers piled up the tools in the gangbox in a way that the travel of the RF signal might be hindered. They, for example, placed deliberately a bunch of metallic tools on top of the tool with the RFID tag attached in order to hinder the RF signal from being detected by the reader.

2. Once all tools in the gangbox were piled up, number of RFID tags detected by the RFID reader within two minutes was measured.

3. The process of loading tools and recording the RFID signals was repeated 30 times.

Workers loaded the RFID tagged tools into the gangbox along with other tools that had no RFID tags attached. While loading tools, the workers tried to cover up the RFID tags with other tools that would hinder the RF signal. Once the tools were loaded into the box, the number of RFID tags identified by the reader within 2 minutes was collected. This hide-andseek type experiment was repeated for 30 times.

Field Tests of RFID Technology for Construction Tool Management

-27-

Smart Chips Project

a) Lid Opened

b) Lid Closed

Figure 4-8) Gangbox with a RFID reader installed

Figure 4-9) Computer application for RFID tag monitoring

Field Tests of RFID Technology for Construction Tool Management

-28-

Smart Chips Project 1

2

3

a) Small-size tools (3 tools)

4

5

6

b) Medium-size tools (3 tools)

7

c) Tool in the tool case Figure 4-10) 7 Tools selected for the field test

Figure 4-11) Tools piled up in the gangbox

Field Tests of RFID Technology for Construction Tool Management

-29-

Smart Chips Project 4.2.3 Results and Interpretations Out of 30 trials, the RFID reader successfully identified all tags within in 2 minutes for 26 times. For 4 times out of 30 trials, the RFID reader failed to identify all tools. Each time it missed only one tool out of seven tools to be identified. Overall, the RFID reader missed only 4 tools out of 210 tools to be identified. It was noticed that the same tool (R6) kept missing for three times. R2 was also missed once. This test was implemented with the gangbox lid opened.

However, when the reader tried to identify tags one more time with the lid closed, all seven tools were identified successfully within 2 minutes. We speculate that the RF signal was less dispersed and kept bouncing back and forth inside the gangbox when the lid was closed, which in turn gave the RFID reader higher chances to detect the RF signal. The result of the Gangbox Test is presented in the Table 4-2.

Table 4-2: Raw measurement of the Gangbox Test Number of tools with the RFID tag attached and jumbled in the gangbox with other tools Number of jumbles and measurements Number of successful identification of all tools within 2 minutes Total number of tools (out of 210 tools) successfully identified in the gangbox Total number of tools (out of 210 tools) missed in the gangbox

Lid Opened

Lid Closed

7

7

30

30

26

30

206

210

4

0

After examining the tool R6, which was missed for 3 times, we noticed that the tool was made of metal and the RFID tag was attached inside the tool as shown in Figure 4-3-b.

We speculated that the material of R6 and the position of the RFID tag might hinder the RF signal from traveling and getting detected by the reader successfully. In addition, after the workers participating in this test were informed that the transmitting of the RFID signal might be hindered by metal or liquid type material, they piled up such tools as big metal boxes or oil containers on top of tools to be identified by the RFID reader, which might contribute to missing the tool. We also speculated that the tool’s location in the gangbox may also affect the tool identification.

Field Tests of RFID Technology for Construction Tool Management

-30-

Smart Chips Project 4.3 The Tool Identification Time Test The Tool Identification Time Test was designed to measure the elapsed time required to scan subject tools.

4.3.1 Experimental Setup A gang box was loaded with a representative set of tools. Nine of these tools were randomly selected as subject tools and had RFID tags attached. The gang box was be fitted with an active RF tag reader. The reader was attached to electrical power and the computer network. A second set of nine similar tools was placed on a counter. A bar code reader was setup to scan the tools.

4.3.2 Methodology For the RF Tag set, the researcher randomly assigned subject tools to a location within the gang box: top shelf, second shelf or bottom of the box. After placing the subject tools on their assigned shelf additional tools were added to the box to simulate a full gangbox. The researcher then ran the RFID reader to identify tools in the gangbox, and recorded the elapsed time to identify all tools.

For the Barcode set, a similar set of nine tools with the barcode attached was laid down on a surface similar to a check-in counter. A crew recruited for the test then began scanning all subject tools with the barcode reader. The researcher recorded elapsed time to scan tools.

A total of 47 observations were made: Nine for the Barcode set and thirty-eight for the RF Tag set. The data collected included the elapsed time to scan nine tools for the RF Tag and Barcode tool sets. For the RF Tag set, the number of subject tools correctly identified per observation by location within gang box was also collected.

Field Tests of RFID Technology for Construction Tool Management

-31-

Smart Chips Project 4.3.3 Results and Interpretations Scan Time - The average scan-time for correctly identifying a tool with an RF Tag was 1.66 seconds per tool. The average scan-time for correctly identifying a Bar Coded tool was 4.92 seconds per tool.

The plot in figure 4-12 gives a strong visual impression that the average scan-time for the RF Tag system is much lower than for the Bar Code system. Since the ranges never overlap on even a single observation, it also suggests that this difference will be significant even though the sample size for the Bar Code system is small (only nine observations). The descriptive statistics offer no evidence contradicting the plot. The t-test strongly confirms that the average time to scan nine tools for the RF Tag system (14.6 seconds) is significantly less than the average time to scan nine tools for the Bar Code system (44.2 seconds). On a per tool basis, the RF Tag system required an average of 1.66 seconds to correctly identify each tool. The Bar Code system required 4.92 seconds. This means it takes three times as long for the Bar Code system to scan a tool as it does the RF Tag system.

Field Tests of RFID Technology for Construction Tool Management

-32-

Smart Chips Project Read Times for Bar Code vs RF Tag 70 60

Time (sec)

50 40

Bar Code RF Tag

30 20 10 0 1

3

5

7

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 Observation Number

Figure 4-12) Read times for Bar Code vs RF Tag Table 4-3) Descriptive Statistics RF Tag Mean Standard Error Median Mode Standard Deviation Sample Variance Kurtosis Skewness Range Minimum Maximum Sum Count

Bar Code 14.60316 0.454762 15.07 15.25 2.803341 7.858722 0.17774 -0.80049 11.72 7.35 19.07 554.92 38

Mean Standard Error Median Mode Standard Deviation Sample Variance Kurtosis Skewness Range Minimum Maximum Sum Count

Field Tests of RFID Technology for Construction Tool Management

44.24778 2.572463 41.9 none 7.717389 59.55809 2.046549 1.371558 24.52 36.51 61.03 398.23 9

-33-

Smart Chips Project Table 4-4) t-Test: Two-Sample Assuming Unequal Variances RF Tag Mean 14.60316 Variance 7.858722 Observations 38 Hypothesized Mean Difference 0 Df 9 t Stat -11.3479 P(T<=t) one-tail 6.19E-07 t Critical one-tail 1.833114 P(T<=t) two-tail 1.24E-06 t Critical two-tail 2.262159

Bar Code 44.24778 59.55809 9

RF Tag Tool Identification - The evidence suggests that the Bar Code system is marginally more accurate. However there are mitigating circumstances that may call this result into question.

One factor is that under the existing experimental setup, the only way to determine if a tool is properly identified in a scan sequence is through the reporting feature of the toolmanagement software itself. Another factor is that the RF Tags in the experiment have internal settings that determine their reporting period. The reporting period is the time interval between successive reports to the tag reader.

Since we wanted the system to work as fast as possible, we set the RF Tags to the lowest value available, 16 seconds. This meant that every 16 seconds each tag would send a signal identifying itself to the reader. Under normal field operations a user would not want this value set so low.

The software vendors theorized that under these conditions, the few times the system failed to properly identify a tool were due to longer data base update time requirements rather than RF Tag identification problems. Since under normal operating conditions this would not occur, they believe the accuracy of the RF Tag system would be at or near 100 per cent.

System Implications and Issues - The evidence in this study suggests that there is some time advantage to using RF Tags rather than Barcodes for tool management. However

Field Tests of RFID Technology for Construction Tool Management

-34-

Smart Chips Project the possibility of a fully automated tool room issue and return system enabled by RFID is by far the most significant advantage of RFID over barcode. RFID also has the potential of producing more accurate records than barcode systems, which require manual intervention and potentially less secure (e.g. barcode tags are easily copied).

The advantage of bar codes is that the labels are cheap and can be attached to tools without concern for safety issues. Additionally, bar code labels do not interfere with operation of the tool. One disadvantage is that they are easily damaged or removed.

RF Tags are more expensive although they can be used over and over if not damaged.

On some tools it may be difficult to attach RF Tags due to tool shape, use or size. The active tags used in this experiment are about as big as a domino, much larger than a bar code label.

RF Tag durability and attachment effectiveness are concerns. In the end, however, RF Tag technology holds the promise of increased productivity of tool-room personnel, reduced capital investment in tools and generally better information regarding tools in support of managerial decisions.

Field Tests of RFID Technology for Construction Tool Management

-35-

Smart Chips Project 5. Conclusions FIATECH Smart Chips members, knowledgeable in tool management issues, expect that RFID technology might have the potential to dramatically improve tool management processes using automated systems that provide accurate and timely information about the status of tools on a construction site. These improved processes would also likely lead to significant savings in tool management. However, one may concern about the reliability of RFID technology in terms of identifying tools especially on construction sites.

The purpose of the field tests presented in this report was to determine whether RFID technology would likely increase efficiency and reliability in tool tracking for construction projects, specifically: 1. To determine the reliability of RFID technology in automatically identifying tools passing through a tool room portal for checking in and out.

2. To determine the reliability of RFID technology in identifying tools stored in a field gangbox.

3. To measure the time saving one can make in the process of checking tools in and out by utilizing RFID technology.

The tests provided empirical evidence to support the technical merit of RFID technology in tool management. The prototype RFID system, fabricated for the test, worked reliably in all of the tests, considering that it was implemented with minimal time and adjustment, and it had not been tested previously. It appears that technical issues encountered during the tests (e.g. occasionally missed tags) could be resolved with relatively little additional system development.

However, some technical issues will need to be investigated before this application of RFID technology can be deployed commercially. These include: 1) Tag Attachment: How can tags be attached/incorporated to the wide variety of tools used on a typical construction project? Attachment would need to be: a) secure (i.e. the tag could not be removed) and b) unobtrusive/safe.

Field Tests of RFID Technology for Construction Tool Management

-36-

Smart Chips Project 2) Durability: How long can tags last? Tags must withstand the rough treatment typical of construction tool usage.

3) Supporting Systems: Additional application would be needed to effectively utilize RFID technology for tool management. For example, the “Gangbox” inventory application would require wireless communication between storage boxes and data collection point(s) across a construction site.

4) Standards: Tool Management RFID systems would need compatible RF communication protocols for application across organizations on a single project (e.g. multiple sub-contractors using RF systems for tool management).

The first two issues above (Tag Attachment and Durability) could best be resolved by tool manufacturers incorporating RFID technology into tools at the factory.

Some

manufacturers are beginning to incorporate RFID technology in limited applications (e.g. passive tags that can record tool usage over time). While these applications have value, they do not yet address the potential for automation of tool issue/receipt and inventory offered by active RFID systems. Necessary supporting systems for wireless gangbox inventory are becoming more common as more and more projects implement wireless LAN to support technical and management communications and data sharing on site. The third issue, Standards, will require a widespread industry consensus on specific standards. While such consensus standards are evolving for passive RFID systems in other industries, these standards do not address active RFID systems, and it appears that standards for active systems may be much slower in developing.

It should be noted that while the tests reported here were encouraging with respect to the technical potential of RFID in tool management, the researchers did not attempt to quantify economic cost or benefit of a commercial application. The economic feasibility of such an application would depend on a number of factors such as: 1) specific beneficial impact to a particular organization 2) cost of the technology, and 3) cost of implementation (e.g. training, system integration, etc.).

Field Tests of RFID Technology for Construction Tool Management

-37-

Smart Chips Project

APPENDICES

Field Tests of RFID Technology for Construction Tool Management

-38-

Smart Chips Project Appendix A - Statistical Comparison of RFID vs Barcode Based Tool Tracking Process In order to determine whether the measurement of one group is statistically significantly different from that of the other group, a two-sample t-test could be employed. Knowing that the two-sample t-test is based on several assumptions: 1) independent samples, 2) sample’s normality, and 3) equal variance, we first checked the normality of our measurements using the ShapiroWilk normality test. The null hypothesis for the Shapiro-Wilk test is that the measurements are drawn from normal population. If the p-value from the Shapiro-Wilk test is less than 0.05 then the hypothesis of the test can be rejected.

The two-sample t-test would be applied when the measurements of both RFID based tool tracking process and barcode based tool tracking process satisfies the normal population.

Otherwise, the nonparametric test, such as Wilcoxson rank sum test, should be employed.

Since none of our measurements satisfy the assumptions for the two-sample t-test, the Wilcoxson rank sum test (also known as Mann-Whitney U test) was employed for our test with 95% of confidence level. Hypothesis we have established is that the population mean of the elapsed time for moving tools with the RFID based tool tracking process is different than the population mean of the elapsed time for moving tools with the barcode based tool tracking process.

Field Tests of RFID Technology for Construction Tool Management

-39-

Smart Chips Project Table A-1) Descriptive results of statistical analysis Categories

Smallsize Tool

Mediumsize Tool

Tool in the Tool Case

Three Tools

Number of Observations Number of Detected Number of Lost Arithmetic Mean Median Standard Deviation Minimum Maximum Shapiro-Wilk Normality Test (p-value) Test employed Number of Observations Number of Detected Number of Lost Arithmetic Mean Median Standard Deviation Minimum Maximum Shapiro-Wilk Normality Test (p-value) Test employed Number of Observations Number of Detected Number of Lost Arithmetic Mean Median Standard Deviation Minimum Maximum Shapiro-Wilk Normality Test (p-value) Test employed Number of Observations Number of Detected Number of Lost Arithmetic Mean Median Standard Deviation Minimum Maximum Shapiro-Wilk Nomality Test (p-value) Test employed

RFID

Barcode

32 32 32 32 0 0 24.10 seconds 26.22 seconds 24.00 seconds 26.00 seconds 3.76 seconds 3.75 seconds 19.00 seconds 22.00 seconds 40.00 seconds 35.00 seconds 0.000 0.005 Wilcoxon rank sum test 30 30 30 30 0 0 24.60 seconds 26.67 seconds 24.00 seconds 26.00 seconds 2.24 seconds 3.26 seconds 20.00 seconds 23.00 seconds 30.00 seconds 41.00 seconds 0.432 0.000 Wilcoxon rank sum test 10 10 10 10 0 0 24.10 seconds 34.10 seconds 24.00 seconds 35.00 seconds 2.18 seconds 3.48 seconds 21.00 seconds 29.00 seconds 28.00 seconds 39.00 seconds 0.413 0.379 Wilcoxon rank sum test (due to sample size) 30 30 90 90 0 0 23.50 seconds 43.60 seconds 23.50 seconds 41.00 seconds 2.62 seconds 9.97 seconds 18.00 seconds 34.00 seconds 30.00 seconds 87.00 seconds 0.518 0.000 Wilcoxon rank sum test

Field Tests of RFID Technology for Construction Tool Management

-40-

Smart Chips Project Table A-1) Descriptive results of statistical analysis (Continued)

Five Tools

Number of Observations Number of Detected Number of Lost Arithmetic Mean Median Standard Deviation Minimum Maximum Shapiro-Wilk Nomality Test (p-value) Test employed

30 30 145 150 5 0 26.97 seconds 51.10 seconds 27.00 seconds 42.50 seconds 2.71 seconds 25.19 seconds 21.00 seconds 34.00 seconds 34.00 seconds 154.00 seconds 0.327 0.000 Wilcoxon rank sum test

Comparison with One Small-Size Tool The arithmetic mean of the RFID group and the barcode group is 24.10 seconds and 26.22 seconds respectively. The difference between these means is 2.12 seconds. The standard deviation of the RFID group and the barcode group is 3.76 and 3.75 seconds respectively. The p-value of the Shapiro-Wilk Normality test indicates that the Wilcoxon rank sum test should be employed. Table A-2 presents the result of the Wilcoxon rank sum test. The resulting pvalue of 0.014 of this test indicates that the null hypothesis can be rejected, which means the population mean of the RFID group is not equal to the population mean of the barcode group.

The box plot in Figure A-1 further indicates that the elapsed time for moving tools with RFID based tool tracking process is less than that of the barcode based tool tracking process.

Table A-2) Wilcoxon rank sum test TIME Mann-Whitney U Wilcoxon W Z Asymp. Sig. (2-tailed)

330.500 858.500 -2.451 0.014

Field Tests of RFID Technology for Construction Tool Management

-41-

Smart Chips Project 50

40

6

30

T IM E

20

10

RFID

Bar-code

Figure A-1) Box Plot

Comparison with One Medium-Size Tool The arithmetic mean of the RFID group and the barcode group is 24.60 and 26.67 seconds respectively. The difference between these means is 2.07 seconds. The standard deviation of the RFID group and the barcode group is 2.24 and 3.26 seconds respectively.

Since the measurement of the barcode group does not satisfy normality requirement s, the Wilcoxon rank sum test was employed to test whether there is any statistically significantly difference between two groups’ measurements. The resulting p-value, 0.003 as shown in Table A-3, of this test indicates that the null hypothesis should be rejected. It is reasonable, therefore, to determine that the population mean of the RFID group is not equal to that of the barcode group. The box plot in Figure A-2 further indicates that the elapsed time for moving three tools at once with the RFID based tool tracking process is less then that of the barcode based tool tracking process.

Table A-3) Wilcoxon rank sum test TIME Mann-Whitney U Wilcoxon W Z Asymp. Sig. (2-tailed)

251.000 716.000 -2.971 0.003

Field Tests of RFID Technology for Construction Tool Management

-42-

Smart Chips Project 50

53

40

30

TIME

20

10 N =

30

RFID

30

Barcode

Figure A-2) Box Plot

Field Tests of RFID Technology for Construction Tool Management

-43-

Smart Chips Project Comparison with one tool kept in the tool case The mean of the RFID group and the barcode group is 24.10 and 34.10 seconds respectively. The difference between sample means is distinctively 10.10 seconds. The standard deviation of the RFID group and the barcode group is 2.18 and 3.48 seconds respectively.

Since the sample sizes are small, we employed the Wilcoxon rank sum test although both measurements satisfy the normality issue.

The p-value of the test marked 0.000, shown in Table A-4, indicates a distinctive difference between two groups. It is reasonable to determine that the population mean of the RFID group is not equal to that of the barcode group. The box plot in Figure A-3 verifies that the elapsed time of the RFID group was significantly less than that of the barcode group.

Table A-4) Wilcoxson rank sum test TIME Mann-Whitney U

0.000

Wilcoxon W

55.000

Z

-3.800

P-value (2-tailed)

0.000

Exact P-value [2*(1-tailed Sig.)]

0.000

50

40

30

TIME

20

10 N =

10

RFID

10

Bar-code

Figure A-3) Box Plot

Field Tests of RFID Technology for Construction Tool Management

-44-

Smart Chips Project Comparison with three tools The arithmetic mean of the RFID group and the barcode group is 23.50 and 43.60 seconds respectively. The difference between these means is 20.10 seconds. The standard deviation of the RFID group and the barcode group is 2.62 and 9.97 seconds respectively.

The normality test indicates that the Wilcoxon rank sum test should be employed. The resulting p-value of the test, which is 0.000 as shown in Table A-5, indicates that the null hypothesis should be rejected. It is safe, therefore, to conclude that the population mean of the RFID group is not equal to that of the barcode group. In fact, the box plot in Figure A-4 shows that the elapsed time of the RFID group is less than that of the barcode group.

Table A-5) Wilcoxson rank sum test Time Mann-Whitney U

0.000

Wilcoxon W

465.000

Z

-6.664

Asymp. Sig. (2-tailed)

0.000

10 0 44

80

60

40

T I M E3 EA

40

20

0 N =

30

RFID

30

Bar-code

Figure A-4) Box Plot

Comparison with five tools

Field Tests of RFID Technology for Construction Tool Management

-45-

Smart Chips Project The arithmetic mean of the RFID group and the barcode group is 26.97 and 51.10 seconds respectively. The difference between these means is 24.13 seconds. The standard deviation of the RFID group and the barcode mean is 2.71 and 25.19 seconds respectively.

The Shapiro-Wilk Normality test indicates that the Wilcoxon rank sum test should be employed for the test. The p-value of the test, which is 0.000 as shown in Table A-6, indicates that the null hypothesis should be rejected. It is reasonable, therefore, to conclude that the population mean of the RFID group is not equal to that of the barcode group. The box plot in Figure A-5 shows that the elapsed time of the RFID group is less than that of the barcode group.

Table A-6) Wilcoxson rank sum test Time Mann-Whitney U

0.500

Wilcoxon W

465.500

Z

-6.657

Asymp. Sig. (2-tailed)

0.000

18 0 16 0

32

14 0 120 31

10 0 80

46 3 46 7

T I M E5 EA

60 40

15

20 0 N =

30

RFID 1

30

Bar-code 2

Figure A-5) Box Plot

Field Tests of RFID Technology for Construction Tool Management

-46-

Smart Chips Project Comparison of measurements within RFID groups In order to investigate whether the number of tools passing through the RFID portal at once would affect the efficiency of the RFID based tool tracking process, we implemented an Analysis of Variance (ANOVA) test. In order for the ANOVA test to yield a robust result, however, each group should be normally distributed.

The result of the normality test presented in Table A-7 indicates that the measurement of the RFID group with one small size tool is not normally distributed. After we examine the outlier of the measurement, we became to believe that the outlier might be caused by confusions that the experiment participant faced when passing through the portal. We finally determined to exclude this outlier from the measurement. The measurement then became acceptable for the normality issue.

Table A-7) Basic Statistics of RFID group Categories 1. Small-size Tool

2. Medium-size Tool

3. Tool in the Tool Case

4. Three Tools

5. Five Tools

Total

Number of Observations Arithmetic Mean Standard Deviation Shapiro-Wilk Nomality Test (p-value) Number of Observations Arithmetic Mean Standard Deviation Shapiro-Wilk Nomality Test (p-value) Number of Observations Arithmetic Mean Standard Deviation Shapiro-Wilk Nomality Test (p-value) Number of Observations Arithmetic Mean Standard Deviation Shapiro-Wilk Nomality Test (p-value) Number of Observations Arithmetic Mean Standard Deviation Shapiro-Wilk Nomality Test (p-value) Number of Observations Arithmetic Mean Standard Deviation

With Outlier

Without Outlier

32 24.10 seconds 3.76 seconds 0.000 30 24.60 seconds 2.24 seconds 0.432 10 24.10 seconds 2.18 seconds 0.413 30 23.50 seconds 2.62 seconds 0.413 30 26.97 seconds 2.71 seconds 0.327 132 24.7273 3.09171

31 23.58 seconds 2.43 seconds 0.550 30 24.60 seconds 2.24 seconds 0.432 10 24.10 seconds 2.18 seconds 0.413 30 23.50 seconds 2.62 seconds 0.413 30 26.97 seconds 2.71 seconds 0.327 131 24.6107 2.79718

Field Tests of RFID Technology for Construction Tool Management

-47-

Smart Chips Project 50

Outlier 40

6

117

30

TIME

20

10 N =

32

30

10

30

30

1

2

3

4

5

Figure A-6) Box Plot with the outlier 40

116

30

T IM E

20

10 N

=

31

30

10

30

30

1

2

3

4

5

Figure A-7) Box Plot without the outlier

Field Tests of RFID Technology for Construction Tool Management

-48-

Smart Chips Project The null hypothesis we established for the ANOVA test is that the population means of the five measurement groups; 1) a small size tool group, 2) a medium size tool group, 3) a tool in the tool case group, and 4) three tools group, and 5) five tools group were not different.

However, the result of the ANOVA test, presented in Table A-8, indicates that the measurement of the five tools group is different from the rest of the groups. In fact, the box plot in Figure A-7 shows that it took longer time to move 5 tools at once than any other cases.

Table A-8) LSD ANOVA Test between the RFID data groups I

J

1. Small-size Tool

2. Mediumsize Tool 3. Tool in the Tool Case

4. Three Tools

5. Five Tools

Mean Difference (I-J)

Std. Error

P-value

95% Confidence Interval Lower

Upper

One Tool Mid-Size

-1.0194

0.6364

0.1117

-2.2789

0.2401

One Tool inside a Tool Case Three Tools

-0.5194 0.0806

0.9037 0.6364

0.5665 0.8994

-2.3078 -1.1789

1.2691 1.3401

Five Tools One Tool Handful Size One Tool inside a Tool Case Three Tools Five Tools One Tool Handful Size One Tool Mid-Size Three Tools Five Tools One Tool Handful Size One Tool Mid-Size One Tool inside a Tool Case Five Tools One Tool Handful Size One Tool Mid-Size One Tool inside a Tool Case Three Tools

-3.3860 1.0194 0.5000 1.1000 -2.3667 0.5194 -0.5000 0.6000 -2.8667 -0.0806 -1.1000 -0.6000 -3.4667 3.3860 2.3667 2.8667 3.4667

0.6364 0.6364 0.9074 0.6416 0.6416 0.9037 0.9074 0.9074 0.9074 0.6364 0.6416 0.9074 0.6416 0.6364 0.6416 0.9074 0.6416

0.0000 0.1117 0.5826 0.0889 0.0003 0.5665 0.5826 0.5097 0.0020 0.8994 0.0889 0.5097 0.0000 0.0000 0.0003 0.0020 0.0000

-4.6455 -0.2401 -1.2957 -0.1698 -3.6365 -1.2691 -2.2957 -1.1957 -4.6624 -1.3401 -2.3698 -2.3957 -4.7365 2.1265 1.0969 1.0709 2.1969

-2.1265 2.2789 2.2957 2.3698 -1.0969 2.3078 1.2957 2.3957 -1.0709 1.1789 0.1698 1.1957 -2.1969 4.6455 3.6365 4.6624 4.7365

Field Tests of RFID Technology for Construction Tool Management

-49-