Abstract: A device for providing self compensation of an operating position servo, as when external forces influence movement of a movable object, for example, when turning a wheel chair seat, has a position encoder for outputting position signal sets and for turning of the movable object, servo circuitry with elements for simultaneously signal handling at least two sets of controlling position signals, each set having at least two positioning signals.

Abstract: A chassis, particularly for carrying a wheelchair with pivotal seat (S), fitted with ground-engaging wheels with at least one driven from a drive device through a drive transmission and with at least one steerably suspended and connected to a steering motor receiving steering signals for steering the chassis bearing while driving from a steering panel comprising steering control devices (STY) is described, whereby all steerably wheels (2R) are drive device driven and steerably suspended each being pivotal about a vertical steering axis (2S, STF) geometrically maintained within or at a vertical plane comprising the wheel axis (2RAKS).