Direct SISO loop design of tracking servo system for optical disk drives

The dual-stage actuators are used in the positioning servo system of optical disk drives. The direct single-variable design (DSD) technique is studied for designing the tracking servo system in which there is a sensor to measure the relative displacement between the two stages. The conclusion clearly given is that a servo system using a dual-stage actuator with multi-variable characteristics can be directly designed as two single-variable systems. The tracking servo system can be designed as two independent servo loops. The multivariable problem can be treated as a single-variable problem. The features and forms of the dual-stage-actuator servo systems are also studied. The control accuracy and robust stability of the system by DSD are investigated. The interaction between the loops is studied by use of an equivalent perturbed model. The simulation of tracking control of the system is presented.