Adaptive Flying Height Control Based On Hybrid Actuator In High-density Optical Disk Drives

Optical data storage has played a crucial role in the information society. With theexplosion of information, new storage technology with higher data transfer rate andhigher storage density is needed. Near-field recording (NFR) breaking through thelight diffraction limit represents a promising technique for optical data storage. NFRcan reach a high storage density with more than150GB/inch2. However the opticalhead-disk spacing will drop down to less than100nm which limits the application ofthe existing far-field recording technology in DVD system. Therefore, the effectivedesign of optical head driving system with a promising servo control method deservesfurther research.This thesis presents the control issue of optical head-disk spacing for the nextgeneration of optical storage system. The main research purpose is to design anadaptive flying height control method based on hybrid actuator in order to attenuatedisturbances. The main contents of this research include the following parts:1、The introduction of the control issue of optical head-disk spacing for the nextgeneration of optical storage system is first presented. Then a hybrid actuator systemwhich combines both advantages of the flying tri-pad slider used in hard disk drivesand the voice coil actuator used in optical disk drives is proposed, and the head-diskinterface dynamical model of this hybrid actuator system with the tri-pad slider isdeveloped.2、The Youla parameterized adaptive controller is proposed to regulate theflying height at its desired value against unknown multiple narrow-band disturbances.The performances of Youla parameterized adaptive controller and lead-lag controllerare compared in the MATLAB/Simulink. Simulation results which show that theYoula parameterized adaptive controller has a better capability to deal with unknownmultiple narrow-band disturbances, and can meet the performance requirements ofthe next generation optical storage systems. 3、Based on the designed hybrid actuator system, an optical storage testplatform is developed for the algorithm verification. The simulation andexperimental results show that the Youla parameterized adaptive controller providesgood accuracy and robustness, and can be applied in the control of head-disk spacingfor the next generation of optical storage systems.