Research On Direct Torque Control And Torque Servo Application For Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor direct torque control(PMSM-DTC)is widely used in aeronautics and astronautics fields and in the industrial automation field due to its simple control structures,dynamic performance,and robustness and so on.In this dissertation,the improvement of direct torque control and its application in dynamic load simulator is as a research object.The main contributions of this dissertation are as follows:1.Due to the torque and flux ripples,the application in high precision torque servo is not widespread for its fast response and dynamic performance.To improve the torque and flux linkage control precision,direct torque control with optimal duty cycle modulation method is proposed for PMSM.The performances of torque and flux linkage control with DTC are analyzed in detail.It is pointed out that the voltage vector selection table and the discrete hysteresis comparator are the main factors causing the torque and flux ripples.The duration time of active voltage vector,also named optimal duty is calculated based on the error of torque and flux.The simulation and experimental results show that the propose method can reduce the influence of the voltage vector selection table and discrete hysteresis comparator.Also,it means that the torque and flux ripples are reduced.2.In addition to the torque and flux ripple,the switching frequency of the voltage inverter is not constant in traditional DTC.The inconstant switching frequency will cause the current and torque distortion,results in poor performance of starting and low speed,not makes full use of the inverter and so on.To solve the problem,model predictive direct torque control(MPDTC)with constant switching frequency is presented for PMSM.The voltage vector selection table in traditional DTC is replaced by the performance evaluation function in MPDTC.Combining with the duty cycle and vector modulation,the PWM with constant switching frequency is generated by the selected active voltage vector and two zero voltage vectors.The torque and flux ripples are reduced.The simulation and experimental results show the effectiveness of the proposed method.Compared with traditional DTC and MPDTC,the proposed method has more excellent dynamic performance and steady state accuracy.The proposed method provides strong support for applying torque control to more high precision applications for PMSM.3.The surplus torque existing in electric dynamic load simulator(EDLS)will affect the accuracy of load torque seriously,which caused by the object motion,friction interference,and the nonlinearity of motor and mechanical mechanism and so on.According to the characteristics of EDLS,a multi closed-loop control strategy is proposed,which puts the speed closed-loop as assisted loop,and put the torque closed-loop as outer loop and the position closed-loop as compensation.The mathematical model of the EDLS using PMSM is developed and the control structures of signal closed-loop and multi closed-loop are presented respectively.A detailed analysis of the EDLS are carried out by the aspects of disturbance rejection,robustness,nonlinear compensation and compared with single-loop torque control at the same time.It shows that the proposed method can isolate the nonlinear of PMSM,the mechanism interference and the interference of the position existing in EDLS.Finally,the experiments are carried out to demonstrate the effectiveness with self-designed experimental platform of EDLS.The experimental results show that the proposed method can eliminate the surplus torque effectively and improve the loading accuracy.This provides powerful guarantee for the steering gear performance testing and has strong significance in engineering applications for EDLS.4.The sine or trapezoidal wave load is commonly applied for the steering gear testing fot test which has the characteristics of periodic.A fractional iterative learning controller is proposed for EDLS which the position and torque closed-loops are applied for feedback control and the iterative learning control is applied for feedforward compensation.The traditional PID and iterative learning control are replaced by fractional order PI~?D~?for position and torque closed-loops and fractional order iterative learning control is used for feedforward compensation.The simple mathematical model of the electric dynamic loading system is established in the frequency domain.The better dynamic response and robustness of the controller are enhanced owing to the information memory characteristics of fractional order calculus.The convergence conditions of the fractional order iterative learning control are presented through theoretical analysis.Finally,testing of the surplus torque and experiment are verified.Compared with integer order PID and iterative learning control method,the controllers are effective in achieving a better torque tracking and restraining the surplus torque for the electric dynamic loading system with fractional order PI~?D~?and iterative learning control.So it can ensure better loading precision and provide more reliable ground experiment equipment for the aircraft performance testing aircraft.This research also can ensure the success rate in aircraft research and has great military significance...