Research On Active Magnetic Bearing Based On H_∞ Theory

As a new support technology,magnetic bearing realizes non-contact support between stator and rotor based on magnetic force,which eliminates the energy loss of traditional ball bearing due to mechanical friction without lubrication.It has a broad application prospect in high speed,high temperature conditions.In the paper,active magnetic bearing that produce controllable electromagnetic force is selected for research.Firstly,the magnetic circuit model of AMB system is established,and the formula of magnetic flux density in the air gap is solved under the condition of ignoring the nonlinear factors such as magnetic flux leakage and hysteresis.Then,the linearized calculation formula of electromagnetic force is derived according to the field energy theory,and the differential control method is used to apply it to the AMB control system.Based on the assumption of rigid rotor,the rotor dynamic model of magnetic bearing is established.Then,as for the problem of low-frequency disturbance and high-frequency model uncertainty of the AMB system,H_∞control method is selected to enhance the robustness of the system.After describing the composition of H_∞standard control and the selection principle of mixed sensitivity control weighting factor,the mixed sensitivity H_∞controller of AMB system is established.On this basis,the simulation model of AMB H_∞control system is built in Matlab,and experimental analysis is compared with the traditional PID control model.Finally,in order to verify the actual performance of AMB H_∞control system,an experimental platform of AMB system is designed,which mainly includes power circuit,drive and isolation circuit,signal sampling circuit,main control circuit based on DSP and other modules,eddy current displacement sensor is used to detect the displacement information of AMB rotor.Then,the levitation experiment of AMB system is carried out.The results show that the H_∞controller designed in this system has fine control performance.At the same time,it is found that H_∞control has strong robustness in dealing with the uncertainty of the system,but it needs to consume a lot of digital computing resources.Therefore,continuous optimization of the program is of great significance to improve the performance of the system,which provides a reference for further research and application.