A new dynamic model of the wheelchair propulsion on straight and curvilinear level-ground paths

Independent-roller ergometers (IREs) are commonly used to simulate the behaviour of a wheelchair propelled in a straight line. They cannot, however, simulate curvilinear propulsion. To this effect, a motorised wheelchair ergometer could be used, provided that a dynamic model of the wheelchair-user system propelled on straight and curvilinear paths (WSC) is available. In this article, we present such a WSC model, its parameter identification procedure and its prediction error. Ten healthy subjects propelled an instrumented wheelchair through a controlled path. Both IRE and WSC models estimated the rear wheels' velocities based on the users' propulsive moments. On curvilinear paths, the outward wheel shows root mean square (RMS) errors of 13% in an IRE vs 8% in a WSC. The inward wheel shows RMS errors of 21% in an IRE vs 11% in a WSC. Differences between both models are highly significant (p < 0.001). A wheelchair ergometer based on this new WSC model will be more accurate than a roller ergometer when simulating wheelchair propulsion in tight environments, where many turns are necessary.