Research On Closed-loop Control System Of Stepper Motors

Stepper motor is the last perform link of control system. But open-loop controlsystem has such problems as oscillation and step out, which have limited theapplication of stepper motor. So the position closed-loop control is introduced toimprove the stepper motor control performance. This thesis is concerned with theresearch on closed-loop control system of the most commonly used three-phasehybrid stepper motor.Current situation of the development and the problems existing in open-loopcontrol system of stepper motor is briefly described. Focus on the analysis of currentsituation of closed-loop control system of stepper motor. Different structure and theproblems existing in closed-loop control system of stepper motor have beenexpounded, leads to the aims and main contents of the research.The structure and operation principle of three-phase hybrid stepping motor isstudied. The mathematical model of the motor is established. Draw a conclusion thatthree-phase hybrid stepper motor can be analyzed as the ac permanent magnetsynchronous motor. Different stepper motor drive technologies are studied to analyzethe advantages and disadvantages of them. Information on position of a stepper motorrotor can be obtained with position sensor or without it. Their advantages anddisadvantages have been analyzedThe id=0control algorithm is commonly used in vector control. Thedisadvantages are presented when it is used in stepper motor control. Instead of, themaximum torque per ampere (MTPA) mode is selected as the control algorithm toimprove the efficiency of stepper motor. The space vector pulse width modulation(SVPWM) technique is studied, put forward the optimization strategy of SVPWMwhich can effectively reduce the times of switch in control, reduce the switching loss.Then motor acceleration and deceleration curve has been analyzed which is importantin closed-loop speed control.Finally, the thesis puts forward the overall structure of the stepper motorclosed-loop control system. The three-phase hybrid stepper motor simulationsubsystem of each state equation is established on Matlab/Simulink simulationplatform. Combined with vector control, subdivision driving control, current and speed closed-loop control, stepper motor closed-loop control simulation system isestablished. Open-loop control simulation system is established as comparison.Simulation results show that, with closed-loop control, the position control accuracyand the reliability of stepper motor performance is significantly improved. Themaximum torque per ampere (MTPA) mode can effectively improve the operationefficiency of the motor.