Research On Torque Ripple Suppression Strategy In PMSM Servo System

The servo system controls the torque and excitation components of the PMSM(Permanent Magnet Synchronous Motor)through vector control to realize the fast response of the electromagnetic torque of the PMSM,and then meet the fast and accurate follow requirement of the position command.Due to the issues of current measurement deviation,motor manufacturing defects,and electronic switch dead zone in the system,the electromagnetic torque of the PMSM will generate periodically pulsation.Based on the PMSM servo control system,various factors that cause the torque ripple in the system is considered,and a torque ripple suppression strategy is proposed in this thesis.The main research in this thesis focuses on the model of motor torque ripple,torque ripple suppression strategies,and research on on-line implementation methods of torque ripple compensation.Firstly,the mathematical expression of torque ripple under the classic vector control framework is analyzed in this thesis.From the perspective of power,the ripple effect is quantified by the DC bias of the current feedback sensor,signal conditioning gain mismatch of the current feedback sensor,and the harmonics of the magnetic field.At the same time,according to the space-time domain conversion theory,the torque ripple in time domain is converted into the expression of the spatial position to simplify the model.Secondly,the method of torque ripple suppression is determined by means of torque current feedforward compensation based on position feedback indexing.By acquiring the periodic pulsation information,a torque current compensation model can be established.Meantime the different characteristics of feedback channel,and forward channel affecting compensation is analyzed,then direct compensation for torque current or compensation after adjustment is decided.Finally,an online method for torque ripple suppression is proposed.Considering that the servo system could suppress the electromagnetic torque ripple in closed loop response and the torque current component contains the torque ripple information.In this thesis,the space domain fast Fourier transform is used to obtain the torque current harmonic information,and a torque current compensation model and compensation mechanism are constructed online.The effectiveness and feasibility of the method are verified through simulation and experiments.