Self-sensing Magnetic Bearings Have Zero Bias Current Control Method Research

In order to accurately measure the change of the air gap between stator and rotor,traditional magnetic bearings need to use multiple displacement sensors,which leads to increased equipment cost and volume,and the detection point and output point are not in the same position,which brings negative effects on the reliability and stability of the whole system.In order to solve this problem,self-sensing magnetic bearing comes into being.In this thesis,the mathematical model of self-sensing magnetic bearing with single degree of freedom is established.The inductance characteristics of magnetic bearing coil are analyzed and studied,and the mathematical relationship between the inductance of coil and the change of rotor displacement is obtained.On this basis,the displacement self-detection method is analyzed in detail,including differential transformer self-detection method and high frequency small signal injection detection method.Aiming at the single-degree-of-freedom magnetic bearing system,the displacement self-detection circuit is designed by using the high frequency small signal injection detection method,and the signal generator circuit,amplifying circuit,precision half-wave rectifier circuit and low-pass filter circuit are simulated by Multisium software.The voltage signal proportional to the rotor displacement is obtained successfully.Secondly,the voltage-controlled system and the fluid-controlled system are analyzed,and the voltage-voltage power amplifier and the voltage-current power amplifier are compared and analyzed.The power amplifier suitable for the selfsensing magnetic bearing system is designed,and the power amplifier circuit is simulated and analyzed.The results show that the power amplifier can successfully convert the control voltage into the control current.You get the electromagnetic force you need.In this thesis,when designing PID controller and fuzzy PID controller suitable for self-sensing magnetic bearing system,the zero bias current control mode is introduced,the corresponding zero voltage comparator and switch gate circuit are designed,and the simulation and optimization of different controllers are carried out with MATLAB software.The results show that the zero bias current mode can not only reduce the loss of magnetic bearing,but also reduce the loss of magnetic bearing.It can also ensure the stable operation of the magnetic bearing system.Finally,the self-sensing magnetic bearing system with single degree of freedom is debugged.