Study On Rotor Displacement Measuring System For Power Magnetic Bearing

Nowadays, the NC machine tool is developing for high speed, high precision and large load direction; the supporting bearing and driving motor are the key technologies to achieve the goal. By following and developing the magnetic levitation technology the power magnetic levitation bearing (power magnetic bearing for short) integrates the torque function into levitation function. The power magnetic bearing which has the advantages of free touch, free friction, high speed, high precision and compact will play an important role in the supporting and driving field of high-speed machine tool spindle.However at present the power magnetic bearing is still in the stage of being studied and trialed and it is hard to be productionized. It is a very important problem for rotor displacement measuring system to precisely measure the displacement of rotor and provide the reliable signal to control the levitation of rotor accurately.The rotor displacement measuring system for power magnetic bearing is studied, the installing and measuring methods and the conditioning circuit for output signal of sensor are designed, the error which is caused by the variance between the sensor measuring coordinate and controlling coordinate is analyzed and the corresponding measure is provided. The linear characteristic of eddy current sensor is analyzed and the linearity correction by the software programming of DSP for sensor is presented.The temperature rises of stator and rotor are worked out and the temperature field distribution in rotor is analyzed. The temperature property of eddy current sensor which is the important device in measuring system is analyzed and the temperature compensating measure by software in temperature field of power magnetic bearing is provided.On the basis of above design and analysis the DSP and eddy current sensor based measuring system for rotor displacement is established.The EMC theory is introduced and the displacement measuring system is designed with EMC technology.Additionally, facing the developing tendency of displacement measuring system the integrated displacement measuring system is presented. The signal conditioning circuit of sensor is integrated with the controlling circuit to establish the base for integrated and intellectualized system and multi-parameter measurement.Lastly, the whole contents are summarized.