Research On Torque Ripple Suppression Strategy Of Permanent Magnet Synchronous Motor

In the context of the national promotion of industrial upgrading,the development of high-end manufacturing has become an urgent need of the times.The control performance of the servo system which is the core component of processing equipment,is a key factor that affects the level of processing.Permanent magnet synchronous motor is often used as an executive device in the servo system,but due to the non-ideal structure of motor and the non-linear factors of inverter,the output torque of the motor contains a lot of harmonics.Torque ripple limits the application of synchronous motors to the field of high-precision manufacturing.For the purpose of improving the smoothness of the output torque of the motor,this thesis studies the torque ripple suppression strategy of the permanent magnet synchronous motor.First of all,this thesis analyzes some factors that cause torque ripple.It is clear that cogging torque,magnetic flux harmonics,dead time effect,and current sampling error are the four causes of torque ripple.Secondly,only for the dead time effect,the equation of harmonic current caused by dead time effect is introduced,and a novel method for detecting the harmonic amplitude is proposed.By controlling harmonic amplitude to zero using closed-loop feedback,this thesis realizes an adaptive dead time compensation method.Secondly,considering that the interaction of current harmonics and magnetic flux results in torque harmonics,torque ripple can be suppressed by suppressing current harmonics,therefore a control scheme is proposed by combining a resonant controller and a PI controller.The general quasi-resonant controller method brings a huge risk of instability to the control system due to the existence of system delay.Thus this thesis proposes a new kind of resonant controller with three degrees of freedom,the solution ensures the stability of system even if motor runs at high speed.Then,because the torque ripple will lead to the speed ripple eventually,which means that it can be known all the information about torque ripple,and so the iterative learning control method is used in the speed controller to suppress the speed ripple,which can indirectly suppress torque ripple at various frequencies.Finally,this thesis builds a simulation model based Matlab/Simulink to verify the algorithm mentioned above.A physical experiment platform is also designed for implementing the vector control system of the permanent magnet synchronous motor.The simulation and experimental results indicate that the control strategies proposed in the article can suppresse the torque ripple effectually,also improve the performance of the control system successfully.