Automatic calibration and servo control scheme for offsetting mechanical

Abstract

In a mechanical device in which a member is moved by an electrical actuator through an electronic and mechanical linkage, apparatus for compensating for changes in system gain to allow precision movement with non-precision components. There a sensor for accurately determining positions of the member, control logic connected to provide a control signal to the actuator, and an adjustable gain control for adjusting the gain of the control signal. Compensation logic is connected to receive positional signals from the sensor, for applying a control signal to the actuator to move the member to a target position closest to a desired final position, for adjusting the gain of the control signal with the adjustable gain control until the member is located at the target position within acceptable tolerance limits, and for then employing that gain to move the member to the desired final position. The method associated with the apparatus can be done in real-time or by pre-calibrating in advance. When pre-calibrating, there is a look-up table containing a plurality of pre-established gains associated with respective ones of a plurality of target positions and the compensation logic selects a gain from the look-up table employs the gain to move the member directly to the desired final position.