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

Recently, two-wheel wheelchair systems had attracted attention since their mobility is better than that of conventional four-wheel wheelchair systems. However, two-wheel wheelchair systems must achieve stabilization control under disturbances caused by modeling error or a road situation since two-wheel wheelchair systems are underactuated systems such as the inverted pendulum. In this study, step passage motion in two-wheel wheelchair systems is considered. A reaction torque observer (RTOB) is employed to estimate the pitch angular interaction torque and the pure external wheel disturbance. Furthermore, repulsive compliance control is employed to determine the optimal pitch angle command to compensate for the center of gravity (CoG) of a human and to assist whole step passage motion. Experimental results are evaluated in terms of comfort for the human by utilizing generalized index ISO2631-1.