Research On Key Technologies Of The Servo Control System For Volume Storage Discs

In recent years,with the rapid development of 5G communication,Internet of Things,artificial intelligence and other technologies,various data has been surging into all kinds of stoage exponentially every year,among which 80% will be stored as cold data.How to keep this massive amount of cold data safe,secure for a long time in a energy-saving,and lowcost way has become an increasingly serious issue that every data centers manager has to be confronted.Homogeneous Medium Volume Optical Data Storage(HMV-ODS)equips with the potential to store tens or even hundreds of terabytes of data in a disc with the size of a standard Blu-ray disc,cheaply and securely.HMV-ODS faces not only the challenges such as smaller recording bits,denser track pitches,and higher revolutional speed as its predecessors(i.e.Blu-ray),but also the major challenge of developing novel servo mechanism for uniform and transparent storage media.Therefore,a dedicated servo layer is introduced into HMV-ODS discs,and servo information is scattered in servo layer and data layers.This study firstly analyzes the controlled object and their control specifications of the servo system serving HMV-ODS discs in detail.The controlled object is the dynamic characteristics of the actuator,which is developed for this bulk optical storage device;the control specifications are proposed after comprehensively considering the signal-to-noise ratio(SNR)of the read-out signal and the cost of disk manufacturing.Taking the performance of actuators and the requirements of SNR into account,a control algorithm is designed based on the traditional lead-lag controller,to compensate the inherent characteristics of the actuator.Therefore,the performance baseline of the optical drive control system is obtained(the lead-lag controller);then,an improved additional repetitive controller is designed for this specific system.Comparison has been made with the performance baseline.It turns out the focus tracking error is reduced,and system robustness is also improved greatly.In this study,an FPGA+DSP heterogeneous optical drive servo control system has been developped,which includes signal sampling module(for FE and TE),data transmission and processing module(between FPGA and DSP),controller module,actuator drive module and PC-end GUI.In this platform,the controller algorithm mentioned above is realized and verified,namely the focusing and tracking servo algorithms.The experimental results are consistent with the simulation results carried out in Simulink.The results obtained by this platform show that the proposed improved repetitive controller reduces the focusing error by 41.3%compared with the traditional controller,and has better robustness.The above work has been verified by Huawei,and it provides a solid software and hardware foundation for the future development of high-density,large-capacity bulk optical storage systems.