The Study On The Method Of Self-Sensing Of Magnetic Bearing Using The Principle Of Differential Transformer

Using the principle of differential transformer,a method of self-sensing rotor position of magnetic bearing is studied in this paper. By this way , no special displacement sensors are used. The bias magnetic field of the bias coil driven by bias current and small signal test current,results in the induced signal of the control coil. The terminal voltage of the control coil is detected by the test circuit. Then the signal containing the information of rotor displacement is obtained ,from which we can get the DC voltage signal proportional to the rotor displacement through half-wave rectification circuit and low pass circuit.This DC signal is put into a PID controller to get the control signal of the rotor displacement. Finally,the control signal is put into the power amplifier to get the control current.Then the closed loop control is realized.The three level bidirectional power amplifier in a switch-mode is designed for the control of radial force. The experiment platform of single freedom , bias current and small signal test current ,and displacement test current are designed and fabricated. The result of experiment makes clear that the method of differential transformer can detect the signal of displacement.