Research On Direct Torque Control For Low Speed And High Torque Permanent Magnetic Synchronous Motor

Along with the development of the manufacturing,as an important part of the numerical control machine and the robot and the elevators etc.,PMSM servo system has been the important domain of the domestic and foreign research and application.Based on the comprehensively deep research on the PMSM's mathematic model and control theory,deep theory and substantially experimental research are made in this thesis on the design of low-speed and high-torque PMSM, Vector Control(VC),Direct Torque Control(DTC),low-speed operation,inverter diagnosis and fault-tolerant operation,sensorless control,high torque load simulator,and a high performance full digital PMSM servo system are developed.Mathematical model of PMSM is presented,it suggests that the rotor field-orientation vector control of i_d=0 can be chosen.The correction,compensation and improvement methods are investigated in this thesis for the conventional DTC PMSM drive systems according to the problems associated with this method.Specific issues examined are:compensation for the variation of the stator resistance,the offset error of the DC bus voltage,the voltage error generated by the forward voltage drop the dead time of the switches,improvement of the steady state performance are major concern in this thesis.Based on the trait of PMSM,and studies the cause of torque and speed ripple of DTC system, when PMSM runs at low speed.Based on the model of PMSM,establishes the simulation model of DTC,and studies the effect of zero-voltage vector to the torque and magnetic flux linkage. Based on the deadtime model,the thesis studies the effect of the deadtime effect to the torque and magnetic flux linkage.The conclusion of theory verifies that the deadtime effect can reduce the torque and impacts on the performance of the system.The thesis proposes voltage compensation formula of deadtime effect.Low speed control performance has much more influence on the precision of systems. To improve the speed response in low speed region is very useful to control systems.So Extend Kalman Filter(EKF) is applied to low speed control of control systems in order to identify the information of position of magnet poles and low speed instead of incremental encoder. Grounded on the work above,a high performance of speed measurement system based on the TMS320LF2407A is developed,and its monitor control system designed based delphi7.0.To take into account the fundamentality of the fault signal detected,and the predominance of wavelet in time-frequency field to analyse and deal with the transient and unbalanced signals and distill signal fault characteristic,takes db1 and db5 wavelet function to diagnose the fault of phase winding and phase-ground in PMSM and to distill current signal fault characteristic and to eliminate noise.simulation has proved that the wavelet analyse can realize the fault characteristic of instantaneous signal to distill and analyse.And the sametime,simulation has been taken and studied about the open-circuit and short- circuit faults in drive system.A rotor flux linkage vector based speed sensorless method is proposed for the PMSM DTC system in this thesis.This theory is equally applicable to fuzzy DTC and SVM DTC.A filter is used to smooth the noise in the estimated rotor speed signal in order to obtain a high performance sensorless DTC drive system.No extra sensor is needed in this method,and it is easy to implement even in a low computing speed microprocessor based drive system.The proposed method is validated by the simulation results of the fuzzy PMSM DTC system.Based on the whole framework of DTC system of PMSM,the thesis proposes the hardware and software methods of DTC system with TMS320F2812 as controller,and discusses that DSP design methods of direct torque controller.The foundation of advancing and analyzing the PMSM load characteristic simulate dynamic model,it puts forward the control principle block diagram of armature current and exciting current and the fuzzy inference control rules of linear torque load,fan pump type load and thruster load and supplying applications to dead zone Bang-Bang-PI complex control algorithm in permanent torque load armature current and exciting current control.It simulates the whole system with MATLAB.The design achieves expected results.Lastly with the system testing and experiment result analysis,it not only indicates load simulation control system high-performance,but also it makes different kinds of complex control algorithm implements run well in the control system.The design achieves the expected purpose.