Research On The Direct Torque Control System For Permanent Magnet Synchronous Motors Based On Extended Kalman Filter

With development of the manufacturing & automobile industry, as an important part of digital control machine tool and robot etc., PMAC servo system has been the important domain of domestic and foreign research/application. Based on the comprehensively further research on PMSM's mathematic model and control theory, further theory and substantially experimental research are discussed on PMSM' s parameters estimation, sensor-less control and direct torque control.In this thesis, a method of PMSM direct torque control (DTC) is presented, and the steadiness condition with MTPF operation is deduced (above base speed, under current limitation) .A PMSM direct torque control based on EKF is presented in this thesis. Performance of DTC system depends greatly on the accuracy of the estimated stator flux and rotor speed, which in turn depends on the proper models and accuracy of the monitored currents and voltages. EKF is based on d-q axis motor model consists of stator current, stator flux linkage, angular speed &position of rotor and other motor parameters (state vector: stator current, stator flux linkage, rotor angular speed & position; input: stator voltage; output: stator current). EKF is designed for stator flux and rotor speed estimation in close-loop control. It can decrease the errors of monitored currents and voltages, improve the estimated accuracy of stator flux and rotor angular speed & position to perform sensor-less control. EKF improves the accuracy of stator flux, and it is robust to parameters change and load disturbance. Since the initial value is not necessary for EKF, the problem, rotor initial position required by DTC, is solved. It is an essential sensor-less control method and its validity is verified by simulation. Finally, an improved method is proposed according to the deviation of the simulation results.Based on the research above, the design of AC regulator based on TMS320F240 DSP is introduced. The feasibility and practicability of the method was discussed according to real time experiment results, and qualities, such as multi-interface, wide speed range, and good dynamic and static performance, has been testified.