Segment filtering iterative learning control for motor servo systems

It is studied the zero-phase filter design problem in iterative learning control (ILC) for motor servo systems. A kind of segment filtering ILC is proposed based on Hilbert spectrum. Firstly, error signal can be obtained after reference trajectory tracking without ILC. With the Hilbert transform, the instantaneous frequencies of tracking error signal can be represented as functions of time. On the basis of the ILC convergence condition and the time-frequency characteristics of the tracking error signal, the zero-phase filter is segmentally designed in order to ensure the monotone convergence of iterative learning process and improve the reference trajectory tracking accuracy. Finally, the trajectory tracking control simulation results verify the effectiveness of the proposed algorithm.