PERCEIVED JACK POSITION DRIFT COMPENSATION METHOD AND APPARATUS

A controller commands a jack drive to extend and retract a jack leg relative to a jack base along a stroke having retraction and extension limits. The controller updates a perceived present leg position value in response to position change signals from a position change sensor. The controller occasionally applies compensation factors to the perceived present leg position value in the extension direction. The controller resets the perceived present leg position value whenever the jack leg reaches the retraction limit.