Research On PMSM New Reaching Law Sliding Mode Control Algorithm Based On Load Torque Observer

Since the 1990 s,with the improvement of and development of permanent magnet materials and control technology,the application of PMSM has been continuously widened,it also puts higher and higher requirements on the control performance of PMSM,the application of advanced control algorithms has great significance to the performance improvement of permanent magnet synchronous motor control system.Sliding mode variable structure control has strong robustness to external disturbances and system parameter changes,it has become one of the most important control strategies in the field of permanent magnet synchronous motor control.In order to reduce the chattering on the premise of ensuring the robustness of the sliding mode control.This paper firstly constructs a velocity loop sliding mode controller for PMSM based on a new reaching law,it uses a combination of the reaching law and the quasi-sliding mode to suppress chattering and introduces the arctangent function of the state variable to design the reaching law and the variable boundary layer saturation function,the motion of the system state is controlled in the approach stage and the sliding mode stage respectively.Then,the compensation of disturbance is increased to further suppress chattering and improve the robustness of the system.It observes firstly the load torque with an extended sliding mode observer,and then observes the disturbance caused by the load torque and viscous coefficient with a nonlinear extended state observer,it can be found that the disturbance observed by the nonlinear extended state observer has no chattering and the observation performance is better by comparing the observation effect of the load-torque with the extended sliding mode observer.Finally,this paper studies the position sensorless control on the basis of the new sliding mode control with disturbance compensation.In view of the influence of buffeting on the disturbance observation of the speed estimation of the traditional sliding mode observer,it tries to avoid that the effect is indirectly transmitted to the sliding mode control by the observation disturbance,by replacing the symbol function with the smooth and continuous sigmoid function and increasing the self-adaptive observation of the back EMF,it weakens the buffeting,improves the estimation accuracy,reduces the influence on the disturbance observation and sliding mode control,and ensures the speed regulation performance of the control system.The simulation model of permanent magnet synchronous motor control system is established in MATLAB/Simulink environment,and the design of each step was verified separately.Simulation results show that: the new reaching law,the variable boundary layer saturation function and the disturbance compensation make the sliding mode control greatly weaken the chattering while the robustness is guaranteed.The nonlinear extended state observer enables fast and accurate observation of disturbances and does not have chattering itself.Sliding mode observation based on sigmoid function and quadratic back EMF self-adaptive observation can effectively suppress chattering while ensuring observation performance,it is hardly passed to the disturbance observation and sliding mode control.The whole control system has fast response and strong anti-interference,which improves the speed regulation performance of permanent magnet synchronous motor very well.