Fuzzy Sliding Mode SVM-DTC System Of Asynchronous Motor With Load Torque Observation

To improve the problems of large flux and torque ripple in the traditional DTC system,this paper applies the sliding mode control to the control system to design the controller,which effectively reduces the torque and flux ripple,but also caused chattering phenomenon in the system.In order to reduce the torque and current ripple while cut down the chattering,the fuzzy sliding mode controller is designed in combination with fuzzy control theory.In addition,the sliding mode load torque is proposed for the unknown and variable load in the actual control system.The scheme was experimentally verified by simulation software.The main contents of this paper are as follows:Firstly,it mainly introduces the research purpose and significance of this article.What's more,the research dynamics of induction motor at home and abroad are also mentioned.Secondly,the principle of direct torque control for induction motor is introduced.The simulation model is built.And the simulation research is carried out by Matlab.Thirdly,the principle of sliding mode control is expounded.The speed,torque and flux controllers are considered to replace PI controller and hysteresis comparators.The simulation model is built and the simulation experiment is carried out by Matlab.Simulation results show that this control strategy can weaken the torque and current ripple of the system with effect.Fourthly,aiming at the chattering phenomenon caused by sliding mode control,combined with adaptive method and fuzzy control theory,the adaptive sliding mode speed controller and fuzzy sliding mode flux and torque controllers have been proposed.Then the simulation model is built and the experiment is carried out to prove the result that the control scheme can effectively improve the chattering phenomenon while reducing the torque and current ripple of the traditional DTC system.At last,in the view of the stator resistance and the influence of pure integrator which existing in the traditional u-i type stator flux observation model leading to inaccurate flux estimation as the motor is subjected in low-speed operation,a new method about double low-pass filters is proposed.For the actual control system,the load is unknown and variable.The sliding mode load torque observer is considered to improve control performance of the system by reducing the uncertainty.According to the relationship between the motor loss model,stator flux,electromagnetic torque and speed in steady state,a hybrid coordination control method based on given stator flux and the optimal stator flux is designed to minimize the losses of the system in steady state.Through the Matlab/Simulink simulation experiment,the new flux observation model can accurately estimate the stator flux when the motor is running at low speed.In addition,the stator flux base on the optimal efficiency during steady-state operation reduces the loss of the system.Furthermore,the torque observer can accurately track load changes and improve the anti-interference ability of the control system.In summary,the direct torque control of induction motor based on sliding mode and fuzzy control theory could reduce the torque and current ripple and improve the chattering phenomenon.While it not only realizes the speed control of the induction motor,but also has good practical application value.