MECHANICAL PERFORMANCE CHARACTERIZATION OF MANUAL WHEELCHAIRS USING ROBOTIC WHEELCHAIR OPERATOR WITH INTERMITTENT TORQUE-BASED PROPULSION A Dissertation Presented to The Academic Faculty by Jacob P. Misch In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy (Bioengineering) in the George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology December 2020 COPYRIGHT © 2020 BY JACOB P. MISCH MECHANICAL PERFORMANCE CHARACTERIZATION OF MANUAL WHEELCHAIRS USING ROBOTIC WHEELCHAIR OPERATOR WITH INTERMITTENT TORQUE-BASED PROPULSION Approved by: Dr. Stephen Sprigle, Advisor Dr. Sharon Sonenblum Schools of Mechanical Engineering & School of Mechanical Engineering Industrial Design Georgia Institute of Technology Georgia Institute of Technology Dr. Aldo Ferri Ramakant Rambhatla, MBA School of Mechanical Engineering Vice President of Engineering Georgia Institute of Technology Invacare Corporation Dr. Frank Hammond III School of Mechanical Engineering Georgia Institute of Technology Date Approved: November 12, 2020 ACKNOWLEDGEMENTS “So many of our dreams at first seem impossible, then they seem improbable, and then, when we summon the will, they soon become inevitable.” – Christopher Reeve I’d like to formally thank my advisor, Stephen Sprigle, for his guidance on nearly every aspect of my career. Day after day, he taught me by example that intelligence and wisdom are only worth as much as the motivation that drives them. I also thank the rest of my committee – Sharon Sonenblum, Aldo Ferri, Frank Hammond III, and Ramakant Rambhatla – for their valuable insight and inspiration. This project would not have moved past the ‘ideation’ and ‘frustration’ stages without them. I share great appreciation for my lab mates, past and present, within the Rehabilitation Engineering and Applied Research (REAR) Lab. Never before have I been surrounded by such like-minded, kind-hearted, and capable individuals. I can humbly say that the students working with me have cumulatively taught me more than I ever thought I could learn. Finally, and of paramount sincerity, the friends and family that have tirelessly supported me for years deserve unmentionable gratitude. Each success was respectfully celebrated together with joy, but perhaps more importantly, every hurdle, delay, cancellation, and rejection were met with optimism and encouragement. My inspiration is fostered by knowing each and every one of you. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS iii LIST OF TABLES vii LIST OF FIGURES ix LIST OF SYMBOLS AND ABBREVIATIONS xiii SUMMARY xiv CHAPTER 1. Introduction 1 1.1 Wheelchair Usage and Coding 2 1.1.1 Wheelchair Categorization 3 1.2 Methods of Wheelchair Testing 5 1.2.1 Component-Level Testing 6 1.2.2 System-Level Testing 7 1.2.3 Advanced Model Testing 9 CHAPTER 2. Specific Aims 11 2.1 Development and Assessment of Intermittent, Torque-Based Propulsion Using Robotic Testbed 11 2.2 Investigation of the Effects of Incremental Mass Additions on Ultra- Lightweight (K0005) Manual Wheelchair Propulsion 12 2.3 Improvement of the High-Strength Lightweight (K0004) Manual Wheelchair Baseline Configuration with Component Selection 12 2.4 Comparison of Performance Between Folding and Rigid Ultra-Lightweight (K0005) Manual Wheelchair Frames 13 2.5 Broader Impacts 13 CHAPTER 3. Anatomical Model Propulsion System 16 3.1 System Overview 16 3.1.1 Anthropomorphic Structure 17 3.1.2 Propulsion System 18 3.1.3 Data Acquisition 21 3.1.4 Data Processing and Analysis 22 3.2 Prior Work 29 3.3 Limitations of Velocity Control 35 3.4 Torque-Based Motor Control 39 3.4.1 Overview 40 3.4.2 Hardware Modifications 46 3.4.3 Clutch Validation 48 3.4.4 Theoretical Controller Derivation 51 3.4.5 Software Modifications 63 3.4.6 Torque Output Validation (Stationary) 67 iv 3.4.7 Torque Output Validation (Over-Ground) 70 3.4.8 Maneuver Generation 74 3.5 Data Collection Procedure 80 3.5.1 Over-Ground Maneuvers 81 3.5.2 Analysis of Over-Ground Data 84 3.5.3 Equivalence Testing 85 CHAPTER 4. Incremental Mass Additions to Frame 91 4.1 Overview 91 4.2 Hardware and Configurations 94 4.2.1 Weight Support 95 4.2.2 Frame Selection 96 4.2.3 Component Selection 97 4.3 Experimental Design 97 4.3.1 Maneuver Selection 97 4.4 Methods 98 4.4.1 Data Collection 98 4.4.2 Data Analysis 99 4.5 Results 102 4.5.1 Coast-Down 102 4.5.2 Straight 103 4.5.3 Slalom 107 4.6 Discussion 111 4.7 Conclusion 117 CHAPTER 5. Improving High-Strength Lightweight with Components 120 5.1 Overview 120 5.2 Hardware and Configurations 124 5.2.1 Frame Selection 124 5.2.2 Component Selection 125 5.2.3 Chair Configurations 126 5.3 Experimental Design 127 5.3.1 Maneuver Selection 127 5.3.2 Test Surfaces 131 5.4 Methods 132 5.4.1 Data Collection 132 5.4.2 Data Analysis 133 5.5 Results 136 5.5.1 Coast-Down 136 5.5.2 Straight (Tile) 137 5.5.3 Slalom (Tile) 140 5.5.4 Straight (Carpet) 143 5.5.5 Slalom (Carpet) 146 5.6 Discussion 149 5.7 Conclusion 154 CHAPTER 6. Comparing Rigid and Folding Frames 156 v 6.1 Overview 156 6.2 Hardware and Configurations 158 6.2.1 Frame Selection 158 6.2.2 Component Selection 161 6.2.3 Chair Configurations 161 6.3 Experimental Design 162 6.3.1 Maneuver Selection 163 6.4 Methods 163 6.4.1 Data Collection 163 6.4.2 Data Analysis 164 6.5 Results 166 6.5.1 Coast-Down 166 6.5.2 Straight 167 6.5.3 Slalom 171 6.6 Discussion 175 6.7 Conclusion 181 CHAPTER 7. Conclusions 183 7.1 Generalizable Knowledge 183 7.1.1 Frame Mass 183 7.1.2 Component-Based Improvements 185 7.1.3 Frame Type 187 7.1.4 Performance of the AMPS 189 7.2 Limitations 192 7.3 Future Directions 193 APPENDIX A. Custom MicroBasic Torque Controller Script 201 APPENDIX B. Methods to Parse Over-Ground Propulsion Data 206 APPENDIX C. Assessment of Maneuverability Via Momentum 217 REFERENCES 220 vi LIST OF TABLES Table 1 HCPCS-assigned medical reimbursement codes for manual 4 wheelchairs. Table 2 Body segment parameters used to inform the design of the AMPS. 18 Table 3 Deceleration values with and without clutch equipped. 50 Table 4 Electromechanical parameters of the AMPS motors. 53 Table 5 Push-rim propulsion characteristics from reviewed literature 77 Table 6 Reported insignificant differences used to inform equivalence and 89 non-inferiority tests. Table 7 Mass and weight distribution of incremental mass configurations. 96 Table 8 Descriptive statistics of coast-down results for each incremental 102 mass configuration. Table 9 Descriptive statistics for cost, distance, and kinetic energy of 104 incremental mass configurations in the Straight maneuver. Table 10 Descriptive statistics for cost, distance, yaw, and kinetic energy of 108 incremental mass configurations in the Slalom maneuver. Table 11 Amount of allowed services and charges from 2017 CMS data 120 Table 12 Overview of configurations used to assess performance of the high- 127 strength lightweight wheelchair. Table 13 Descriptive statistics of coast-down deceleration values for the 137 lightweight frame configurations, over linoleum tile. Table 14 Descriptive statistics for cost, distance, and kinetic energy of K0004 138 configurations in the Straight (Tile) maneuver. Table 15 Descriptive statistics for cost, distance, and kinetic energy of K0004 141 configurations in the Slalom (Tile) maneuver. Table 16 Descriptive statistics for cost, distance, and kinetic energy of K0004 144 configurations in the Straight (Carpet) maneuver. Table 17 Descriptive statistics for cost, distance, and kinetic energy of K0004 147 configurations in the Slalom (Carpet) maneuver. Table 18 Rigid-frame K0005 wheelchair selection. 159 Table 19 Folding-frame K0005 wheelchair selection. 159 Table 20 Mass and weight distribution of folding and rigid K0005 frames. 162 Table 21 Descriptive statistics of coast-down deceleration values for the 167 folding and rigid K0005 frame configurations, over linoleum tile. vii Table 22 Descriptive statistics of each outcome variable (Straight Tile 168 maneuver) for the folding and rigid K0005 frame configurations. Table 23 Descriptive statistics of each outcome variable (Slalom Tile 172 maneuver) for the folding and rigid K0005 frame configurations. viii LIST OF FIGURES Figure 1 Overview of the AMPS subsystems. 16 Figure 2 Motor 'hand' with shaft-mounted pinion gear and ring gear push- 19 rim. Figure 3 Control diagram for original velocity-control of AMPS motors. 21 Figure 4 Detailed view of the signal pre- and post-Butterworth filter. 23 Figure 5 Top-down schematic of MWC used to derive system kinematics 24 from drive wheel rotation, from [78]. Figure 6 Representative data output of the ‘Straight’ maneuver in velocity- 28 control mode. Figure 7 Simplified MWC diagrams with non-conservative forces and 31 torques acting on the frame in each maneuver. Figure 8 ‘Canonical maneuvers’ to replicate common aspects of wheelchair 32 motion. (Top) Straight maneuver. (Mid) Fixed-wheel turn maneuver. (Bottom) Alternating zero-radius turn maneuver. Figure 9 (Left) Instrumented coast-down cart. (Right) Scrub torque rig. 33 Figure 10 The ‘Push’ and ‘Recovery’ phases of the wheelchair propulsion 36 cycle. Figure 11 Representative velocity and torque of a straight over-ground AMPS 37 trial in velocity-control mode. Figure 12 Representative velocity and torque of a straight over-ground trial as 38 proposed for the AMPS. Figure 13 Brushed DC motor performance chart from manufacturer. 41 Figure 14 Torque-speed relationship of DC motors. From [87]. 42 Figure 15 (Left) Motor torque calibration rig. (Right) Image of pulley 44 attachment point and load cell position. Figure 16 Calibration curve of the left motor comparing the torque constant of 45 the manufacturer to actual torque outputs.