ELECTRIC POWERED WHEELCHAIR DRIVING OUTDOORS: THE IDENTIFICATION OF DRIVING OBSTACLES & STRATEGIES AND THE DEVELOPMENT OF AN ADVANCED CONTROLLER by Benjamin Arthur Salatin BS in Mechanical Engineering Technology, Old Dominion University, 2006 Submitted to the Graduate Faculty of the School of Health and Rehabilitation Science in partial fulfillment of the requirements for the degree of Master of Science in Rehabilitation Science and Technology University of Pittsburgh 2011 ssssssssssss UNIVERSITY OF PITTSBURGH SCHOOL OF HEALTH AND REHABILITATION SCIENCE This thesis was presented by Benjamin Arthur Salatin It was defended on September 30, 2010 and approved by Dan Ding, PhD, Assistant Professor, Department of Rehabilitation Science and Technology Jonathan Pearlman, PhD, Assistant Professor, Department of Rehabilitation Science and Technology Thesis Director: Rory A. Cooper, PhD, Distinguished Professor and FISA/PVA Chair, Department of Rehabilitation Science and Technology ii ELECTRIC POWERED WHEELCHAIR DRIVING OUTDOORS: THE IDENTIFICATION OF DRIVING OBSTACLES & STRATEGIES AND THE DEVELOPMENT OF AN ADVANCED CONTROLLER Benjamin Arthur Salatin, M.S. University of Pittsburgh, 2011 Copyright © by Benjamin Arthur Salatin 2011 iii ELECTRIC POWERED WHEELCHAIR DRIVING OUTDOORS: THE IDENTIFICATION OF DRIVING OBSTACLES & STRATEGIES AND THE DEVELOPMENT OF AN ADVANCED CONTROLLER Benjamin Arthur Salatin, M.S. University of Pittsburgh, 2011 THESIS ABSTRACT When an electric powered wheelchair (EPW) user leaves the confines of their home and ventures into the outdoors, they are confronted with a wide variety of terrain and driving conditions. Very little research has been done in trying to understand the difficulties EPW users face when driving outdoors. The first section describes a focus group study of 31 EPW users with the objective of assessing EPW users’ comfort level when driving in various outdoor conditions. Questionnaire and focus group transcripts showed that the EPW user’s top concerns were slipping, getting stuck, and tipping. The driving conditions most avoided were in the general themes of soft surfaces, angled surfaces, and adverse conditions. The second section presents in detail the electronic and mechanical design of an advanced controller for an EPW. A single board computer provides the computational power and storage space needed to execute normal operations, complex safety algorithms, and extensive data logging. Sensors provide feedback on velocity and inertia. A rugged aluminum enclosure protects the electronics. The advanced controller is used to research better ways to provide safety and customization for the EPW user. The outcome of this project was to demonstrate what can be done with an EPW to enhance the mobility and safety of its occupant. iv TABLE OF CONTENTS PREFACE .................................................................................................................................. XII 1.0 INTRODUCTION ........................................................................................................ 1 1.1 THE ELECTRIC POWERED WHEELCHAIR .............................................. 2 1.2 DRIVING OUTDOORS ...................................................................................... 8 1.3 ORGANIZATION OF THE THESIS ................................................................ 9 2.0 PART 1 – THE IDENTIFICATION OF DRIVING OBSTACLES & STRATEGIES ............................................................................................................................. 10 2.1 INTRODUCTION ............................................................................................. 10 2.2 METHODS ......................................................................................................... 11 2.2.1 Participants .................................................................................................. 11 2.2.2 Data Collection ............................................................................................ 12 2.2.3 Data Analysis ............................................................................................... 14 2.2.4 Data Credibility/Trustworthiness.............................................................. 16 2.3 RESULTS ........................................................................................................... 17 2.3.1 Questionnaire .............................................................................................. 17 2.3.2 Targeted Coding (Focus Group Transcript) ............................................ 23 2.3.3 In-Vivo Coding (Focus Group Transcript) .............................................. 26 2.3.3.1 Hard Surfaces ...................................................................................... 27 v 2.3.3.2 Soft Surfaces ........................................................................................ 29 2.3.3.3 Angled Surfaces ................................................................................... 30 2.3.3.4 Adverse Conditions ............................................................................. 31 2.3.3.5 Training & Accidents .......................................................................... 33 2.4 DISCUSSION ..................................................................................................... 35 2.4.1 Limitations ................................................................................................... 39 2.4.2 Application................................................................................................... 40 2.4.3 Future Work ................................................................................................ 44 2.5 CONCLUSION .................................................................................................. 45 3.0 PART 2 - DEVELOPMENT OF AN ADVANCED CONTROLLER .................. 46 3.1 INTRODUCTION ............................................................................................. 46 3.2 METHODS ......................................................................................................... 49 3.2.1 Mechanical Design ...................................................................................... 50 3.2.2 Electrical Design .......................................................................................... 53 3.2.3 Power Consumption Tests .......................................................................... 62 3.3 RESULTS ........................................................................................................... 62 3.3.1 Power Consumption Tests .......................................................................... 62 3.3.2 Refinement ................................................................................................... 63 3.4 DISCUSSION ..................................................................................................... 66 3.4.1 Application................................................................................................... 67 3.5 CONCLUSION .................................................................................................. 71 4.0 FINAL CONCLUSION ............................................................................................. 72 APPENDIX A .............................................................................................................................. 74 vi APPENDIX B .............................................................................................................................. 83 APPENDIX C ............................................................................................................................ 206 BIBLIOGRAPHY ..................................................................................................................... 213 vii LIST OF TABLES Table 1: List of Driving Conditions Evaluated in the Questionnaire ........................................... 13 Table 2: EPW User Demographics ............................................................................................... 18 Table 3: Wheelchair Use & Style ................................................................................................. 18 Table 4: Wheelchair Driving Training .......................................................................................... 19 Table 5: Targeted Codes Used ..................................................................................................... 23 Table 6: Krippendorff’s Alpha Test for Coded Categories ......................................................... 25 Table 7: Hard Surfaces.................................................................................................................. 28 Table 8: Soft Sufaces .................................................................................................................... 29 Table 9: Angled Surfaces .............................................................................................................. 30 Table 10: Adverse Conditions ...................................................................................................... 32 Table 11: Training......................................................................................................................... 33 Table 12: Reported Accidents ....................................................................................................... 34 Table 13: Questionnaire Categories Over 50% ...........................................................................