Patent ID: 7015670

Claim:
The method of controlling an electromechanical servomechanism for moving an output member relative to a variable load, said servomechanism including: a motor having a plurality of coils adapted to be supplied with currents and having a permanent magnet rotor with an output shaft; a mechanical transmission arranged between said output shaft and said load, said transmission having a mechanical friction related to said load; a servoamplifier arranged to supply currents to said motor coils in response to an input signal; a command signal for commanding the position of said load; a load position feedback signal compared to said command signal and arranged to produce an error signal; and means for generating an offset signal that is summed with said error signal to modify the input signal supplied to said servoamplifier, said offset signal generating means comprising the steps of: generating said offset signal as a function of said command and feedback signals and the currents supplied to said motor coils after the position of said output member has remained substantially constant for a predetermined time; and adjusting said offset signal so that the sum of the motor currents is reduced until the load position changes such that said servoamplifier input signal will be modified so as to minimize the steady-state power dissipation in said motor.