Assisted control of step passage motion and its comfort evaluation in two-wheel wheelchair systems

Two-wheel wheelchair systems have been attracting attention because their mobility is better than that of conventional four-wheel wheelchair systems. However, two-wheel wheelchair systems must achieve stabilization control in the presence of disturbances caused by modeling error or the road situation, since these systems are underactuated systems similar to the inverted pendulum. In this investigation, step passage motion in two-wheel wheelchair systems is considered. A reaction torque observer was employed to estimate the pitch angular interaction torque and the pure external wheel disturbance. Repulsive compliance control was employed to determine the optimal pitch angle command to compensate for the center of gravity of the user and to assist the whole step passage motion. Experimental results are evaluated in terms of user comfort by utilizing the ISO 2631-1 generalized index.