Abstract
This paper discusses the method of a focus servo system design for a video disk player.
For a conventional focus servo system, a phase delay-lead compensation has mainly been used because we owned much know-how about it. Gain variations of each optical head have been eliminated by gain adjustment. This adjustment, however, introduces the problems, such as uneven control performance and higher cost.
We considered applying the robust model matching method, which enables us to omit the gain adjustment. This method brought in some difficulties like reconciling robust stability with low sensitivity and reducing the degree of controllers. We overcome them by using a reduced model and properly designing the model matching system and the robust filter. We also confirmed the validity of this method by experiments.
