Novel Step Climbing Control for Power Assisted Wheelchair Based on Driving Mode Switching

This paper describes a novel step climbing control scheme for electric power assisted wheelchairs. "Electric power assisted wheelchair" which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people. This research aims at realizing the safe and reliable step climbing motion control of power assisted wheelchairs because power assisted wheelchairs are in danger of overturning backward when raising the front wheels due to the excessive driving torque and of stopping in front of steps when the rear wheels try to climb over steps due to the insufficient driving torque. This paper proposes a novel step climbing control scheme for power assisted wheelchairs based on driving mode switching. The first driving mode, "front wheel raising mode", applies torque control system with the variable assistance ratio to prevent the dangerous overturning. The second driving mode, "rear wheel climbing mode", applies position control system based on the polynomial trajectory to surely climb over steps and stop at the suitable position. The mode switching control based on these two driving modes can generate the safe and reliable step climbing motions. Some experiments show the effectiveness of the proposed control system