Study On Sliding Mode Control For Permanent Magnet Synchronous Motor Based On A New Combined Reaching Law

Permanent Magnet Synchronous Motor(PMSM)has the advantages of simple structure,small size and high power density,so it is widely used in industrial fields,and has achieved remarkable result.The advantages of the Sliding Mode Control(SMC)is simple design and good robustness.Therefore,SMC has become a research hotspot of PMSM control system,which is a kind of nonlinear system with strong coupling and multi-variable.Sliding mode control is a kind of switch control,and it will superimpose a chattering because of the inertia.Chattering reduces the performance of the system and may make the system unstable.Therefore,it is the great significance to study the buffeting reduction of sliding mode control.In order to weaken the chattering of sliding mode control,a new combined reaching law is proposed,which combines the power reaching law with the variable reaching law.At the same time,a new smooth function is used to replace the traditional switching function.Since the control law of the speed loop of the system is in integral form,in order to prevent the speed regulator from entering saturation state,a feedback anti-integral saturation control is added in this thesis.By comparing simulation with traditional PI control,general exponential reaching law and fast reaching law which is in literature,the results show that the new combined reaching law can maintain the shortest adjusting time of the system and weaken the chattering of the system output.And the parameters of the new combined reaching law have a wide range of application.In order to obtain the speed information of the motor,a new sliding mode observer(SMO)is designed in this thesis.The new SMO is based on the idea which is weakening chattering for the reaching law.The power reaching law function is introduced to replace the control law of the traditional sliding mode observer,and the switching function is replaced by the new smooth function.Compared with the traditional sliding mode observer,the high frequency chattering of the new sliding mode observer is weakened obviously,and the speed tracking error of the system is reduced.