Improvement of performance of a tracking servo system for an optical disk drive

A tracking servo system for high-speed and precise tracking control is proposed. An optical disk camera-recorder to record and retrieve high-definition television signals is being developed. The camera-recorder must have both a high data transfer rate and a large capacity. These requirements will be fulfilled by narrowing the track pitch on the disk and by increasing the disk rotation speed. Generally, optical disks have a radial run-out of up to approximately 100 pm peak-to-peak. The tracking servo system must have precise control for the narrow track pitch and high-speed control for the high disk rotation speed. To meet these requirements, we propose a tracking servo system consisting of a feedback controller and of a feedforward controller which employs a pre-compensator applying the zero phase error tracking method. The simulation results show reduction of the residual tracking error and also an increase in the disk rotation speed.