Sliding Mode Variable Structure Control Technology Research For Induction Motor Of The Electric Vehicle

Electric drive control system is the core part of electric vehicle, its performance affectsthe operation of electric vehicles. According to the performance requirements of electricvehicle electric drive control system, this paper studied the speed sensorless vector controlsystem of induction motor for electric vehicles.In the induction motor speed sensorless vector control system, an accurate estimate ofthe speed and flux required motor parameters match. When the speed and flux estimatesimprecise, it will affect the performance of the control system. In order to improveaccuracy and robustness of the control system to parameter fluctuations, this paper studies akind of rotor speed and rotor time constant identification technology using sliding modeobserver. Firstly, through the analysis of the state equation of induction motor in two-phasestationary coordinate system, this paper derived with the stator current and rotor flux statequation with the same coupling. Then the sliding mode control function takes the place ofthe same coupled of rotor flux and stator current equation, the stator current and rotor fluxequation decouple in the two phase stationary reference frame. Finally, according to thesliding mode control stability conditions derived sliding function gain. Using low pass filterand an equivalent function, estimated rotor flux, rotor speed and rotor time constant.In order to decrease the high frequency chattering and accelerate the velocity ofapproach, this paper studies a kind of adaptive sliding mode control gain of the slidingmode current controller. The controller can automatically adjust the gain of sliding modecontrol function based on the disturbance signal, so avoid a lot of calculation ofthe disturbance signal limits. When the sliding mode variable is far from the slidingsurface, it can automatically increase the gain of sliding mode control function, acceleratethe velocity of approach, improvement of its dynamic performance.when the slidingmode variable is near the sliding surface, it can automatically reduce the gain of slidingmode control function, attenuate the high frequency chattering on the sliding surface. TheLyapunov stability theorem analyse the stability of the controller.When the load is lower than the rated load, operation efficiency of the vector controlsystem is low. In order to improve the operation efficiency, this paper studies a sliding mode efficiency optimization method. It establishes the iron loss model of the inductionmotor in the two phase stationary frame, derives the optimal flux using function extremum.The rotor speed and flux as optimization objective, it designs a super helix sliding modecontroller. Using Lyapunov stability theorem to derive the gain of the controller, the controlstability is analyzed. When Sliding mode convergence to the sliding mode surface, theactual speed of the rotor tracks to the set speed, rotor flux tracks to the optimal flux.Based on the TMS320LF2812fully digitalexperimental platform, the statorcurrent sliding mode observer and adaptive gain sliding mode controller are studiedby experiment, the experimental results verify the effectivenessof the algorithm.