Over 200,000 people in the United States use electric-powered wheelchairs (EPWs) as their primary means of mobility. Electric-powered wheelchairs provide functional mobility for people with both lower and upper extremity impairments. While electric powered wheelchairs have made great advances over the past 20 years, the control algorithms remain virtually unchanged since the early 1980s. The simple proportional-integral (PI) controller used on electric-powered wheelchairs for velocity control is antiquated, and does not perform well with disturbances, sensor uncertainties and load variations. In addition, wheelchair users may encounter different environments and road conditions when driving outdoors. The PIs have successfully implemented the shared control system for a pushrim activated power assisted wheelchair. In addition, kinematic and dynamic models of an EPW were developed to simulate the wheelchair motion and were validated by experimental results. With these preliminary studies, the PIs propose to design a robust controller for electric powered wheelchairs that includes velocity control and traction control. The velocity control algorithm based on an improved wheelchair model aims to improve the safety and efficacy of EPWs in the face of external disturbances, parameter variations and uncertainties. The traction control algorithm coping with wheel slips and cases where the wheelchair becomes stuck will increase mobility and ensure safe navigation under less favorable surface conditions (i.e., wet grass, iced sidewalk, snow). Finally, they propose to test the algorithms in a pilot setting, including dynamic stability test, obstacle climbing ability test, operation under caster orientation disturbances, indoor threshold test, operation on ramps, on cross slopes, on grass, on rough surfaces and slippery surfaces. This pilot study will provide the means to conduct a large-scale trial designed to implement robust controllers in electric powered wheelchairs and test the effect on safety, mobility, and community participation.
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