Research On Speed Control System Of Induction Motor Based On Fuzzy And Sliding Mode Control

Due to the inherent low cost of the machine manufacturing,high reliability,large capacity and convenient maintenance,squirrel cage induction motor(IM)drives have gained broad application in industrial plants and household appliances.However,induction motor is a complex control object of electromagnetic coupling to realize energy interaction,in which many problems including parameter optimization in wide range speed regulation,load mutation,perturbation of model parameters and inherent nonlinear factors of induction motor needs to be solved to satisfy the control demands of high performance.Therefore,research on fuzzy and sliding mode control(SMC)strategy of squirrel cage induction motor,speed sensorless technology and rotor flux observer to improve the reliability and speed control performance in complex working environment has been researched and demonstrated by experiments.Firstly,the back-to-back structure of IM speed control system is built.The correctness and effectiveness of the rotor flux oriented vector control system based on back-to-back structure is verified by MATLAB/Simulink simulation and experiments.Secondly,on account of the high precision and fast dynamic response of induction motor in large speed range,fuzzy control is used to adjust the parameters of PI controller.This method makes the setting value of the PI controller parameters close to the optimal value in the whole range.Meanwhile,the offline look-up table is adopted to realize fuzzy controller,which decreases the computational burden.Thirdly,to deal with the internal parameter variations and external disturbances in IM system,an extended sliding mode disturbance observer is proposed to estimate the perturbations.The stability and chattering suppression,which determines the principle of parameter selection,is analyzed.Then,the sliding mode speed controller is established with the feedforward compensation of disturbances,which improves the disturbance rejection effect of IM system.Meanwhile,a hybrid SMC and PI controller with fuzzy logic rule is proposed to reduce the chattering problem in SMC and has faster dynamic response and less overshoot compared with PI control.Finally,based on traditional sliding mode observer(SMO),a fuzzy SMO is proposed to estimate speed and rotor flux of IM.The speed adaptive law and the stability of the flux observer are derived.The selection principle of sliding mode gain is designed by fuzzy control and speed error,which avoids the delay problem caused by low-pass filter.Then,the contradiction of stability and chattering suppression in SMO based on saturate function which employs the linear control instead of the switch control in the boundary layer is analysed.Thus,the observer output can effectively be softened by fuzzy controller adjusting sliding mode gain.The estimated speed can be more accurate and faster.