Research On Reaching Law Sliding Mode Control Technology Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)has been widely used in industry,transportation and other fields because of its small size,high power density and reliable operation.With the increasing demand for speed regulation performance of permanent magnet synchronous motor,the speed control strategy also needs to be improved.Sliding mode control has the advantages of strong robustness and fast response,so it is very suitable for permanent magnet synchronous motor control system,but it also has the disadvantage of chattering.In this paper,the permanent magnet synchronous motor is taken as the research object.Based on the sliding mode control strategy,the sensorless control technology of improved reaching law sliding mode control,high-order sliding mode direct torque controller,sliding mode speed controller based on improved reaching law,sliding mode load torque observer and nonsingular terminal sliding mode observer are studied.Firstly,the main causes of chattering are analyzed through the principle of sliding mode control.In order to weaken chattering,the reaching time of fast power reaching law is studied,and an improved fast power reaching law is proposed based on fast power reaching law.The improved reaching law adds the system state variable to the power term,which can accelerate the convergence speed of the system and effectively suppress the chattering.Secondly,the direct torque control system of permanent magnet synchronous motor is improved by using sliding mode control technology,and the direct torque sliding mode controller based on super twisting sliding mode is designed to replace the hysteresis controller to reduce the torque ripple problem;the sliding mode speed controller based on improved fast power reaching law is designed to replace the PI speed controller to solve the speed overshoot problem and speed up the speed control The improved power term is introduced into the load torque observer,and the sliding mode load torque observer is designed to enhance the anti-interference ability of the system.Finally,in order to save the cost of the speed control system and enhance the reliability of the system,a nonsingular terminal sliding mode observer is designed to observe the back EMF.The normalized phase-locked loop is used to obtain the rotor speed and rotor position,which saves the low-pass filter and improves the observation accuracy.The bandwidth of the normalized phase-locked loop is not affected by the speed and improves the anti-interference performance.Considering the problem of re switching with speed,the sliding mode observer method fails when the motor is powered off.The system uses the short-circuit current vector method to estimate the speed and position of the motor rotor.Combined with the sliding mode observer method,the sensorless control in complex working environment is realized.