A Castor Wheel Controller for Differential Drive Wheelchairs

This paper describes a motion controller for differential drive vehicles with a compensation for castor wheel turn forces. The controller has been developed for electric wheelchairs with two front castor wheels, which require large steering forces to move into the direction given by the joystick in situations where a sharp turn of the castor wheels is needed. It computes the required forces to turn the castor wheels and modifies the drive request adequately. This also helps physical or cognitive impaired users who otherwise have to compensate castor turn forces manually using the joystick, which requires fast reaction time (e.g. when the castor wheels turn quickly into the driving direction) to avoid collisions.