A Research On VCM Positioning System For Mechanical Hard Disk

Precision manufacturing is crucial to the future development of the country.Mechanical hard disk has the advantages of low cost,scalability,high disk density,high capacity,fast transfer speed and fast access.The mechanical hard disk VCM(Voice Coil Motor)positioning system is a positioning system that aims to study the positioning accuracy and positioning speed of the swing-arm VCM head within a mechanical hard disk.The VCM positioning of this system consists of a swing-arm VCM and a secondary micromotor.The positioning process is divided into two steps: the first step allows the swing-arm VCM to drive the head to the vicinity of the target point,and the second step enables the secondary micromotor to guide the head to the target point.This paper focuses on the first step of mechanical hard disk VCM positioning process,in order to improve the efficiency of VCM head positioning,this study introduces a new position feedback loop,high-precision magnetic encoder AS5600 in the first step positioning.this study also adopts a control method with two degrees of freedom control and initial value compensation,It can effectively improve the positioning speed and positioning accuracy of VCM positioning of mechanical hard disk.The main work is as follows:1.Firstly,this paper will study in depth the drive mechanism of the mechanical hard disk VCM positioning system,including the structure of the swing arm VCM,the principle of electric power,modeling the VCM using current drive and the resonance model of the mechanical hard disk VCM drive,and finally analyzing the frequency domain identification algorithm for the VCM to derive an accurate mathematical model.2.Secondly,in order to improve the positioning accuracy and reduce the positioning time of the mechanical hard disk VCM positioning system,the magnetic encoder AS5600 is introduced as the closed-loop position feedback of the whole positioning system,and the two-degree-of-freedom control and initial value compensation strategy are selected as the control algorithm of the whole system.3.Finally,in order to verify the positioning performance of the whole mechanical hard disk VCM positioning system,a closed-loop control system with STM32 as the main controller was built.The experimental results show that the use of magnetically encoded AS5600 as closed-loop position feedback works well,and the positioning system with two-degree-of-freedom control and initial value compensation has faster positioning speed and higher positioning accuracy compared with other positioning systems,which is helpful for the research in the field of mechanical hard disk VCM positioning,and its research content can be extended to the research in the field of modern high-speed precision motion control.