Abstract: A controller for a wheelchair motor or the like including two power transistors each having a base and a collector-emitter path, the collector-emitter paths being connected in parallel. At least one oscillator and a flip-flop are provided to supply pulses alternately to the transistor bases so that the transistors are never turned on simultaneously. In another system, two or more transistors are connected in parallel and are gated on in digital succession responsive to the outputs of a ring counter.

Abstract: A third caster wheel is mounted between the main wheels of a power wheelchair to engage the terrain over which the wheelchair travels. Turning of the wheelchair from a straight line course as a result of uneven terrain is immediately corrected by initially sensing the turning with the third caster wheel. A signal responsive to turning of the caster wheel stem is fed to the left and right wheelchair drive motors to increase the speed of one and decrease the speed of the other so as to return the wheelchair to its straight line course. The caster wheel sensing and feedback system is disabled when an intentional turning of the wheelchair is carried out with the conventional joy stick.