Research On Vector Control System Of Asynchronous Motor Based On Sliding Mode Control

With the popularization of asynchronous motor applications,the higher control performance has also been proposed.Vector control has been gradually applied and improved as one of the high performance control methods for asynchronous motors.In this thesis,the asynchronous motor vector control system is taken as the study object.Through the study of its velocity controller and observer,a new practical exploration for improving the robustness,accuracy and response speed of vector control systems is provided.For the asynchronous motor vector control system,the dynamic performance of the traditional PI speed controller is limited.So a fast double-power sliding mode speed controller is designed.The chattering of this speed controller is relatively small due to the variable approach speed of the fast double power approaching law.In order to further suppress chattering,sliding mode control and fuzzy control are combined.The output of fuzzy controller is used to replace the symbol function in the sliding mode control,which not only can make the discontinuous switching signal continuous to soften sliding mode control,but also can reduce the size of the approaching speed by designing the fuzzy rule,and the chattering is weakened.In order to solve the problem that the traditional mechanical measurement method increases the cost and destroys the structural characteristics of the motor when acquiring the rotational speed and the magnetic chain in the asynchronous motor vector control system,a observer based higher order non-singular terminal programis is first proposed in this thesis.Under this method,the discontinuous symbol function is added to the first derivative of the output,so the chattering can be effectively suppressed after integration.To further reduce the chattering,the quasi-sliding mode control is introduced,replacing the symbol function with a saturated function,which allows the system to be continuous in the neighborhood of the sliding surface to reduce chattering.Finally,in order to avoid the use of the arctangent method which error is directly introduced into the division,software phase-locked loop technology is used to extract the rotor flux angle in this thesis.According to the scheme in this thesis,the models are built based on Matlab/Simulink.The simulation results show that the speed controller designed in this thesis is robust,the response speed is faster,and the chattering effect is more obvious.The error of the observer is smaller,the chattering is weaker,and the convergence speed is faster.