Virtually active elevator hitch

A virtually active hitch system for damping oscillations of an elevator car during vertical motion of the elevator car along an elevator travel path and for leveling the elevator car to adjust for load changes when the elevator motor is braked, the elevator car being connected by a rope to a sheave mounted to an elevator motor, the rope being connected to the car through a hitch assembly in a manner permitting limited relative vertical motion there between, the system comprising:

• means for providing a motion command signal which corresponds with an elevator travel profile dictated by a desired destination of the elevator along the elevator travel path;
• spring means effectively connected between the rope and the elevator car and operative in a semi-active hitch mode to provide a vertical spring force there between;
• controllable damping means and adjustment means effectively connected between the elevator car and the rope and being responsive to a damping command signal in the semi-active hitch mode for selectively impeding relative vertical displacement between the elevator car and the rope and being responsive to an adjustment command signal in an active hitch mode for selectively adjusting the relative vertical displacement between the elevator car and the rope;
• means for providing signals indicative of the measured vertical motion of the elevator car;
• and
• control means responsive to the motion command signal and to the measured car motion signal for determining operation in the semi-active hitch mode and providing a damping command signal to selectively control the damping means and for determining operation in the active hitch mode and providing an adjustment command signal to selectively control the adjustment means.