Application of frequency-following servocompensator to tracking control

A servocompensator with performance of frequency following is applied to a tracking control system whose reference signal includes sinusoidal components. The applied servocompensator is characterized by using signals synchronized with the reference signal in calculating the control input by means of convolution integral. Since the transmission zeros of the closed-loop system are generated at the same locations as the unstable poles of the reference signal automatically, the pole-zero cancellation necessary for asymptotic regulation is achieved. To demonstrate the efficacy of the servocompensator, an experimental apparatus is developed in which the position of a pick up is controlled to hold the distance between the pick up and a rotating disk. In such systems, the misalignment of the disk causes the reference signal to include sinusoidal components. The control error was remarkably reduced at any rotational speed by the servocompensator.