US Patent 7467596 Trim tab control

A trim tab control system determines current tab position based upon a feedback signal that represents incremental motion of the actuator drive motor. Prior to power down, the current tab position is stored in non-volatile memory, and is retrieved on power up. The control system characterizes the actuator during a learning function by driving the actuator between the upper and lower limit positions and counting the number of increments. The display of tab position is based upon the current tab position count and the number of increments in a full range of motion. Automatic up and down commands cause the actuator to be driven up or down until a stop command is received or a limit position is reached.