A Comparison of Different Assistance Strategies in Power Assisted Wheelchairs using an Optimal Control Formulation

Vinicius I. Cuerva, Marko Ackermann, and Fabrizio Leonardi

Keywords

Push-rim activated power wheelchair, optimal control, Wheelchair propulsion

Abstract

Power assisted wheelchairs are a promising solution to overcome problems associated with manual wheelchair propulsion, such as the incidence of upper limbs injuries and muscle fatigue. However, there are still open questions regarding the most appropriate assistance strategy. The main goal of this paper is to compare three different types of assistance in power assisted wheelchairs: constant force, proportional force and a novel type of assistance inspired on the impedance control theory. The comparison was per formed using a simple model and an optimal control for mulation that searched for optimal user actuation and controller parameters so as to minimize the user effort. The fairness of the comparison was ensured by imposing an up per bound on the energy consumption by the motors. The results show that the proportional and impedance control based strategies are the most appropriate steady state conditions. In typical daily activities such as obstacle avoidance, the impedance control has advantage as it permits a faster system’s response.

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