Performance assessment of a pushrim-activated power-assisted wheelchair control system

Wheelchairs are an important form of mobility for people with disabilities. For many years, there have only been three wheelchair varieties: electric-powered wheelchairs, scooters and manual wheelchairs. Recently, wheelchairs have been developed that use a combination of human power and electric power. The human power is delivered by the arms through the pushrims while the electric power is delivered by a battery through two electric motors. The shared control system for a pushrim-activated power-assisted wheelchair (PAPAW) must account for the human behavior and the interaction with the device. The PAPAW uses a form of gain scheduling based upon events recorded from the pushrim torque. The control system significantly altered (p<0.05) selected variables from pushrim torque curves for manual wheelchair propulsion and PAPAW operation as desired. The peak torque was reduced by over 50%, and the time on the rim was nearly doubled with the PAPAW. The PAPAW provided intuitive control and was capable of significantly reducing the strain on the upper extremities commonly associated with secondary disabling conditions among manual wheelchair users.