Patent ID: 6876168

Claim:
A method to attenuate the influence of disturbances including both internal disturbance and external disturbance for a servomechanism having a moveable actuator, a servo motor to provide output torque for positioning said actuator relative to a target position, a servo control mechanism including a power amplifier that provides a command voltage signal to said servo motor, said servo control mechanism further including an actuator position sensor that generates a position signal and a position controller that generates a command signal to said power amplifier, a servo motor current sensor that provides a current signal, a velocity sensor or a state observer to provide a velocity signal, an acceleration sensor that provides the acceleration of said actuator, an acceleration controller, and an acceleration feedback control loop, said method comprising: selecting a separation frequency; estimating the acceleration of said actuator from at least one of said current signal, said velocity signal and/or said position signal in the low-frequency range below said separation frequency, providing an estimated acceleration feedback to said acceleration feedback control loop, and providing a current feedback from said current signal in the high-frequency range above said separation frequency, said low frequency range and said high frequency range being separated by said separation frequency; attenuating said disturbances in said acceleration feedback control loop; and generating a command voltage signal from said acceleration controller in response to a difference between said command signal to said acceleration feedback control loop and said acceleration feedback.