Research On Control Method Of Magnetic Bearing Based On Sliding Mode Variable Structure

With the acceleration of industrial pace,traditional bearings can not keep up with the needs of modern industry,and can not meet the performance requirements of high precision,high speed and low wear.So people take magnetic bearing as a new type of bearings to adapt to the contemporary era and make in-depth research.Therefore,magnetic bearing has become the focus of research in the world.Active magnetic bearing has the advantages of non-contact,low energy consumption,long life and high precision.Based on these advantages,this paper focuses on its controllability.This paper also designs a controller based on sliding mode variable structure control for the controllability of active magnetic bearing system.Then,the theoretical feasibility of this design is verified and analyzed by comparing the results of simulation experiments with relevant performance indicators.Firstly,a high-precision model of active magnetic bearing system is established.Based on the composition and working principle of single-degree-of-freedom magnetic bearing system,its rationality is simplified and its magnetic force is analyzed.The mathematical model of single-degree-of-freedom magnetic bearing system is obtained,which is described by state space equation and transfer function.Based on the study of single-degree-of-freedom magnetic bearing,the multi-degree-of-freedom magnetic bearing system is further studied,and a reasonable Four-Degree-of-Freedom radial high-precision mathematical model is established according to the above steps and methods.Secondly,on the basis of the established high-precision model,a fuzzy sliding mode controller is designed for the single-degree-of-freedom magnetic bearing system.Firstly,a sliding mode controller based on exponential reaching law is designed.The advantages and disadvantages of the sliding mode control are obtained from the theoretical and simulation results,and further improvement schemes are proposed for the chattering phenomenon.On the basis of the designed sliding mode controller and the fuzzy control,the parameters of the sliding mode controller are automatically adjusted by the fuzzy control,so that the system can get better control effect.The model is built and simulated by MATLAB/SIMULINK software.Finally,in view of the non-linearity,uncertainty and multi-input and multi-output characteristics of the radial Four-Degree-of-Freedom maglev system,a fast Terminal sliding mode controller is proposed.Considering the chattering of sliding mode control and the slow convergence speed of the non-linear sliding mode,a global fast Terminal sliding mode controller with fast convergence speed and chattering elimination is proposed.The design is verified by the final simulation.The controller is feasible and has better control effect than traditional control.Figure [36] table [3] reference [59]...