Electric wheelchair control for avoidance of collision and downhill turning

This paper presents a controller design of an electric wheelchair for avoiding collision and downhill turning. The presented method for collision avoidance is based on the information from inexpensive distance sensors so that it may be widely used at low implementation cost. The presented method considers the nonholonomic constraints of a typical differential wheel drive system by employing the model reference control, in which command input signals from an operator is modified to avoid the collision by using the reference model. Next, three approaches to compensating for the gravitational effect when crossing a slope; inclination sensor feedback, disturbance observer based feedback and body´s angular velocity feedback. Experimental results with seven operators in a narrow crank course show the effectiveness of the proposed collision avoidance control by which variance of command input signals are reduced for all the operators. In addition, experimental results of crossing a slope exhibits that the disturbance observer based design is effective to avoid the downhill turning without an inclination sensor.