Study On The Direct Torque Control System Of Special Equipment Low Speed Electric Spindle

As an emerging technology in the field of NC machine tool in recent years，electric spindle gets more and more attention and makes motor spindle motor andmachine tool spindle become a new spindle system. In particular, with the developmentof micro-processor, power electronics and the in-depth study on the motor controltechnology, the control technology of electric spindle is highly promoted. Especially,with the direct torque control of asynchronous motors being put forward, the directtorque control system of electric spindle has become a new hotspot.Based on the dynamic balancing machine as the research platform，A newlow-speed electric spindle direct torque control system of dynamic balance machinebased on the DSP control chip of TMS320F2812is designed on the basis of in-depthstudy on the principle of direct torque control system based on Space Vector PulseWidth Modulation (SVPWM) and the characteristics of the electric spindle direct torquecontrol system. Through simulation and experimental test, the performance of controlsystem has been tested and evaluated. The research contents are as follows:(1) On the base of the asynchronous motor, the direct torque control strategy ofasynchronous motors is introduced. The mathematical models under differentcoordinate systems are analyzed by using the theory of coordinate transformation. Thenthe components between torque and magnetic field of stator are directly controlled byusing the stator-field-oriented technology. At the same time, SVPWM modulationalgorithms and implementation methods have been analyzed. Then a dual closed-loopdirect torque control system of the low-speed electric spindle is designed.(2) The simulation model of the low-speed electric spindle direct torque controlsystem on this basis of Space Vector Pulse Width Modulation has been established byMatlab/Simulink. The coordinate transformation module, speed comparison module,torque and flux linkage calculation module, torque controller module, flux controllermodule and optimal vector control module etc are did special construction. Then someperformance of the control model had been simulated and analyzed. The simulationresults prove that the above model’s dynamic process accords with practical speedregulating process.(3) According to the principle of electric spindle direct torque control, the flowcharts of the hardware and software on the low-speed electric spindle direct torque control system are designed by using the DSP chip TMS320F2812. The hardwaresystem include the circuit design and parameter selection of main circuit (rectifiercircuit, filter circuit and inverter circuit), the control circuit (IGBT drive circuit, current,voltage sampling circuit and the fault circuit), speed and position detection circuit andauxiliary circuit. The software design includes the main program, interrupt subroutine,coordinate transformation program, current the sampling program, speed measuringprogram, PI adjustment program and the SVPWM algorithm program, etc.In addition, comparing with the simulation data, the experimental results andproblems in experiment are analyzed and discussed. All of these lay the foundation forthe further research and development of high performance of the dynamic balancemachine electric spindle control system.