Research On High Performance Sliding Mode Control PMSM Vector Speed Control System

In view of the high power density,simple structure as well as energy efficiency,permanent magnet synchronous motor(PMSM)is becoming an upmarket mainstream product of motor gradually.Naturally,it has higher requirements for speed regulation performance.Overall,the traditional method of speed regulation is PID control.However,the method can be easily influenced by the changes from the external environment and internal parameters.Meanwhile the method is quite limited for the application in complex systems and high-performance requird systems.Sliding mode variable structure control,because of its strong robustness,great stability and fast speed response,is taking over from PID control step by step to be a mainstream control strategy used in motor speed control system.However,the disadvantage is that the discontinuity of the switch will cause chattering in the system and affect the control effect of the system.This is also its major drawback in the real utilization.The motor speed performance requirements are very high,especially in some high precision control fields,so the research of high-performance sliding mode control PMSM vector speed control system is an important practical topic.In order to lighten the overshot chattering of PMSM speed regulating system,raise the response speed,strengthen the observation accuracy and enhance the ability of anti-interference,the traditional sliding mode control is improved and innovated.The main work contents are as follows:1.After reviewing a lot of literature and analyzing and summarizing,based on traditional sliding mode control,a variable exponential approach law is proposed.Then the approach time is analysed and is made comparisons with the traditional law.To validate the strengths of the variable exponential reaching law,its control performance in the classical control system is simulated and compared with that of the traditional exponential reaching law,whereupon a sliding mode velocity controller is built according to variable exponential reaching law.After that,its stability is analyzed by using Lyapunov function,a simulink simulation model was built.2.Using mechanical sensors will raise cost and impair the stability of systems.As a result,no position sensor control for PMSM is studied.When the author used the traditional sliding mode observer to exam the back electromotive force,a train of problems were found including chattering,and low observation accuracy of rotational speed and rotor position.To solve the problems,the author replaced the traditional constant velocity approach law with the exponential approach law.Then a piecewise compound power function fun was designed due to the discontinuity of the switch of the sign function,and the curve characteristics were analyzed with the smoothed sign function(sign),saturation function(sat),hyperbolic tangent function(tanh),and S-type function(sigmoid).Finally,it is concluded that the curve features of the function fun match with the features of the sliding mode control more.3.The cut-off frequency of the low-pass filter is automatically processed to suit the volatile operating conditions of the motor.For secondary filtering,a Kalman filter is devised,forming a Kalman filtered back electromotive force observer.It filters out the high frequency harmonic signal and interference noise signal further carried in the back electromotive force,so as to obtain a smoother and more accurate back electromotive force value curve.The normalized phase-locked loop is used to replace the arctangent function to avoid the amplification of highfrequency chattering caused by sliding mode,and enhance the anti-interference ability.4.Using MATLAB/Simulink online simulation platform,the above improved strategy is applied to the complete system,and a simulation model is made,whereupon the analysis of the comparative test is carried out.The results show that,no matter what state the motor is in,compared with PI controller and exponential reaching law speed controller,PMSM vector control speed regulation system shows good dynamic and static performance under the control of variable exponential reaching law speed controller,whether in improving response speed,suppressing overbuffering,or improving anti-interference and robustness.The sensorless control system of PMSM with the improved sliding mode observer has better control effect than the same system with the traditional sliding mode observer.Chattering is significantly suppressed and the observation accuracy is greatly improved,both in the observation of back electromotive force and the observation of rotational speed and rotor position information.Overall,the expected effect has been reached,proving the effectiveness of the improved method.Whether in the observation of the back electromotive force,or in the observation of rotational speed and rotor position information,buffeting has been significantly suppressed,and the observation accuracy has been greatly improved.Overall,the expected effect has been achieved,verifying the effectiveness of the improved method.