Control developments for wheelchairs in slope environments

We have developed an observer and controllers for wheelchairs in slope environments in this paper. We select two problems that frequently happen in power-assisted wheelchair caused by gravity. The first problem lies in overturning of wheelchairs and the second problem occurs when the difficulty happens in propulsion of wheelchairs on a hill. The former is related to the observation problem, and the latter is related to the control problem. We would like to propose solutions to the both problems. The observer, which we would like to propose here can estimate three main physical values; (1) the speed of the wheelchair, (2) the leaning angle of the wheelchair body from the ground, and (3) external disturbances. The observer can sensor-fuse the informations from three sensors, which it uses the Kalman filter theory. In order to prevent the problem of the wheelchair´s overturning, assistive power by the motor attached to the wheelchair should be decreased according to the state of the wheelchair concerning the leaning angle and its angular velocity. By this, it can realized by using the proposed observer and varying assistance-ratio controller.