Research On Direct Instantaneous Torque Control Strategy Of Permanent Magnet Assisted-switched Reluctance Motor Based On Fuzzy PI

The Permanent Magnet assisted-Switched Reluctance Motor(PMa-SRM)adds permanent magnets to the stator poles of the switched reluctance motor to increase the power density and has the advantages of simple structure,low cost,high fault tolerance and fast dynamic response.However,the inherent biconvex pole structure and nonlinear electromagnetic characteristics make the torque pulsation and vibration noise high,which limit the further application.In this paper,a Direct Instantaneous Torque Control(DITC)method based on fuzzy PI and a nine-interval PWMDITC control method are studied with the goal of reducing torque pulsation as follows:Firstly,the internal structure and working principle of PMa-SRM are analyzed;the basic equations of the motor are described,and linear,quasi-linear and nonlinear mathematical models are established;the nonlinear torque and magnetic chain of the motor are obtained with the help of finite element analysis software,and more accurate winding currents are inverse performed by current interpolation,and a high-precision nonlinear model is built in Simulink,which provides a basis for the simulation and verification of the subsequent control method.Secondly,the conventional DITC system is introduced,and a direct instantaneous torque control system based on fuzzy PI is proposed for the problem of slow speed tracking of PI controller on the speed loop.The fuzzy control method is analyzed,a fuzzy PI controller is designed,the affiliation function and fuzzy control rules are established,and the PI parameters are adaptively adjusted according to the speed error and the error change rate,so that the reference speed can be tracked quickly.Simulation experiments show that the speed tracking of the DITC based on fuzzy PI is stronger,and it reaches the steady state in 0.02 s under the conditions of500r/min speed and 5N·m load.Again,to reduce torque pulsation,a nine-interval PWM-DITC control system based on fuzzy PI is given.A rotor mechanical angle is divided into six intervals,and a hysteresis loop control strategy is planned on each interval;according to the inductance characteristics,it is subdivided into nine intervals again,and a PWM-DITC control strategy is designed to adapt to the characteristics of each interval.Simulation experiments show that the nine-interval PWM-DITC control strategy based on fuzzy PI has a more obvious suppression of torque pulsation,which can be maintained at 10% under the speed of 500r/min and load of 5N-m,while the torque pulsation under the six-interval DITC control is 32%,which is 22% higher than the former,verifying the effectiveness of the nine-interval PWM-DITC control strategy based on fuzzy PI.DITC control strategy based on fuzzy PI is validated.Finally,the PMa-SRM experimental platform was built and the prototype was tested.Hardware circuits such as power conversion circuit,driver circuit,overcurrent protection circuit,current and position detection,and subroutines such as initialization,interrupt and speed were designed and fabricated.The experiments verified the effectiveness of conventional DITC and fuzzy PI-based DITC on speed tracking,and the effectiveness of six-zone DITC and nine-zone DITC on reducing torque pulsation.