Research On Vector Control Of Permanent Magnet Synchronous Motor Based On Sliding Mode Variable Structure

Permanent magnet synchronous motor(PMSM)has been widely used in People's life,industrial production,aerospace and other fields because of its high power density,large torque inertia,wide speed range and so on.However,PMSM is a multivariable,strongly coupled and time-varying nonlinear system.The traditional PI control method is easy to be affected by external disturbances and parameter changes,which makes the speed and current control performance of the motor not guaranteed.Moreover,in some bad working environment,the position sensor of the motor is vulnerable to interference,which directly affects the accuracy of the rotor position,and then indirectly affects the control performance of the motor.In order to improve the control performance of PMSM,the sliding mode variable structure theory is used to design the controller and observer to meet the requirements of high performance control.This paper first describes the mathematical model of PMSM,analyzes the basic principle of vector control and SVPWM,and builds the simulation model of MATLAB/Simulink.On this basis,the basic principle of sliding mode variable structure is introduced in detail,and several sliding mode approaching laws are analyzed.The sliding mode velocity controller is designed by selecting suitable sliding mode switching surface,and the sliding mode current controller is designed to reduce electromagnetic torque ripple.The stability of the sliding mode controller is proved,and the feasibility and effectiveness of the designed controller are verified by simulation and experiment.Then,in order to solve the problem that the system's robustness is not high and the steady-state precision is relatively low,the influence of incomplete decoupling is caused by ignoring the inaccuracy of system parameters and uncertain disturbances such as load in approach law sliding mode control.By analyzing the characteristics of terminal sliding mode,a novel Nonsingular fast terminal sliding mode(NFTSM)is studied.The sliding mode avoids the singularity of terminal sliding mode and improves the convergence speed.The influence of load disturbance is considered in the design of speed controller,and the influence of incomplete decoupling because of the inaccurate system parameters in the design of current controller,so that the robustness of the system is further enhanced and the steady-state precision of the system is improved.The control performance of the motor under the NFTSM control and the approach law sliding mode control is analyzed by simulation,and the superiority of the former control performance is proved.Finally,a sensorless control system based on a Nonsingular fast terminal sliding mode observer(NFTSMO)is studied.A control law with integral term is designed through the NFTSM surface,which can effectively improve the observation accuracy and reduce the buffeting.The low pass filter and rotor position compensation are eliminated,and the system structure is simplified.The stability of the proposed control algorithm is proved by using Lyapunov function.The simulation and analysis of the position sensorless control system of NFTSMO and the position sensor control system of traditional sliding mode observer show that the former has better control performance.