Research On Micro-position Sensors For The Magnetic Suspension Hard Disk

When the hard disk uses the magnetic suspending technology, the contact between the bearings and rotor will be eliminated, which not only can improve the rotor speed of the CD a lot, but also has many advances that other bearings can not have, such as high precision, low vibration, low temperature, low wasting power and no noise etc.The control system is the key element of the magnetic suspending system. The ears of the control system are sensors, they affect the quality of the control. The multi-sensors are used in the control system of the magnetic suspending bearings. The size and installation of the traditional sensors much limit the miniaturization of the hard disk. In order to minimize the size of the hard disk, the micro position sensor of the magnetic suspending hard disks is described in the paper according to the following sides.The internal and overseas development about the magnetic suspending hard disks and the micro position sensor are introduced in this dissertation. The paper also introduces the working principle of the magnetic suspending hard disks and the fundamental concept and methods about MEMS. On the bases of the research about the magnetic suspending hard disk, the paper brings forward a magnetic suspending hard disk based on coupling magnetism activation.On the bases of the coupling magnetism activation, in order to find the appropriate sensors that can fit the system, the paper provides several none-touch position sensors that use different physical principals, such as electronic magnetic, optical, and static electronic principles, and analyzes the advantages and disadvantages respectively, then confirms the position sensors that can fit the system which are the inductive position sensor, the eddy current position sensor and the optical reflection position sensor and introduces the working principles of the three position sensors as well.The design of the micro eddy current sensor is concretely introduced from themicro coils to the control circuit. The sensors have been put outsides of the rotor in the previous magnetic suspending hard disk system, which results in a too big system. Here the sensors are put inside of the rotor, which minimizes the volume of the system a lot. Through the analysis of the different controls, such as P, PD, PI, PID, a result is concluded that the PID control is more effective to the system. Finally the paper brings forward a control method to the sensor and the hard disk.The developing trend of the magnetic suspending hard disks is prospected based on the whole article in the end.