Research On Speed Identification Of Speed Sensorless And Algorithm Refinement Under The Working Condition Of Variable Load Torque

The application of the speed sensorless technology can reduce the cost, and improve the reliability and the environmental compatibility in the AC motor speed regulating system. Model reference adaptive method is one of the speed sensorless methods for the speed identification. It possesses some properties such as high stability, less computational complexity and the easier hardware implementation. Based on these, we make some investigations which can be summarized as follows.Firstly, the current development and research status of speed identification algorithms for speed sensorless technology are introduced. The main objective in this thesis is determined according to the problems arising in practical applications.Secondly, the direct torque control system of an asynchronous motor is introduced and modeled. The traditional speed regulator and torque regulator are improved, and the nice performance is obtained and verified by a simulation experiment.Thirdly, the study is focused on whether the identified speed can track the actual motor speed changing at the initial stage of system running. A method of initializing training for the speed identification modules is proposed. Also, a simulation experiment is given to demonstrate the effectiveness of our results.Finally, the speed estimation error is regulated via the relationship between the load torque and the identification error. Step 1, acquire the speed identification error corresponding to load torque under large numbers of simulation experiments on the Matlab/Simulink platform, process this data and find out the mathematical relationship between them with the help of the least square method. Step 2, set up error correction modules based on the achieved mathematical relationship, improve the original speed identification modules, and confirm the availability of the error correction modules. Step 3, simplify the operation process by using the two-point calibration method instead of the least square method according to users’ requirement. Step 4, confirm that the relationship between the load torque and the identification error is independent of the motor model. The application scope of the improved speed identification module is thus enlarged greatly.This paper improves the performance of the speed regulator system for speed sensorless based on the model reference adaptive control, which possesses some practical significance in engineering.