| Active Magnetic Bearings (AMB) have such a lot of advantages that it is called a technology revolution in the bearings. Applying magnetic suspension technique to the supports of HDD (hard disk drive), it have a lot of advantages in comparison with other bearing types, for example, contact free, absence of mechanical friction and wear etc. In design of HDD suspended by AMB, it is one, of difficulty and emphases that active control for rotor according as the signal of displacement. Main purpose of this paper is aiming at the problem of displacement measuring about HDD rotor suspended AMB, designed a set five degree - of - freedom (5 -DOF) measuring system.The probe's linearity, temperature and dynamic characteristics are analyzed base on principal theory of eddy-current displacement sensor, such as the influence of the coil Q value to the linearity characteristic, influence of the diameter of coil to the linearity characteristic, influence of coil resistance to the temperature characteristic, influence of the measuring coil to the syntony loop. Finally, this paper brings forward to the betterment means for making sensor probe .The circuit of signal procession module are introduced. It expounds the important parts, for example, design of oscillatory, design of demodulation circuit, design of signal filter circuit. The key results of circuit debugging are offered etc. it illuminated that those circuits are consummate for transform displacement signal to hard disc' rotor suspended by AMB.Finally, it discussed the integration of displacement measuring system for hard disk' rotor suspended by AMB and put forward a project of integration about more parameter measuring for sensor.The developing trend of AMB in the future is prospected based on the conclusion of the whole article in the end.
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