Servo Synthesis for an Optical Pick-up Head with Tilt Compensation

Authors:	Yen Jia-Yush, National Taiwan University, Taiwan Ouyang Ko-Hsin, National Taiwan University, Taiwan
Topic:	4.2 Mechatronic Systems
Session:	Data Storage Devices and Micro-Actuation
Keywords:	Optical disks, Nonlinear systems, Robust control, Uncertainty

Abstract

The new DVD optical heads are equipped with tilt control mechanism to compensate for the disk tilt. From the servo point of view, the tilt control shares the same push-pull tracking error (PPTE) signal from the optical head and are compensating the same control goal. In addition, the system exhibits highly nonlinear characteristics due to the change in the lens tilt. This study derives the optical head nonlinear dynamic model based on the Newtonian mechanics. The model indicates that the nonlinear effects mainly arise from the variation in the lens tilt. With reasonable approximations, it is possible to separate these nonlinear factors and lump them into a system variation term. The popular  synthesis procedure is then used for the controller design.