Research On Multi - Modal Control Strategy Of Stepping Motor Position Servo System

Open-loop control of stepper motor has obvious advantages, it’s not only low-cost, not requiring feedback devices such as expensive sensor or photoelectric encoder, but also simple and easy to operate, making the accuracy requirements can be meet within a certain range. However, due to the increasing accuracy requirements of current various industries, the open-loop control of stepper motor has been limited in a wide range of application, the low-frequency oscillation problem and high-frequency step-losing problem are urgent to solve. Currently, for the most widely-used two-phase hybrid stepper motor, how to establish a precise mathematical model and realize precise and stable position-control with intelligent algorithm has become the development direction of the industry.The paper has deeply studied the structure, principle and operation characteristic of two-phase hybrid stepping motor, achieved current control scheme of two-phase hybrid stepping motor by dq coordinate conversion and SVPWM technology, and on the basis of this scheme achieved servo system overall scheme by controlling speed loop and position loop of stepping motor. The paper has completed the hardware design of servo system with DSP28335 as control chip and built completely closed-loop position servo system. For uncertainties such as nonlinearity of two-phase hybrid stepping motor during running, the paper has adopted GA-RBF neural network algorithm to identify the motor system, obtaining mathematical model of two-phase hybrid stepper motor system, laying the foundation for the study of control strategy.Based on fuzzy control and fuzzy PID control, the paper has proposed multi-modal position-control strategy, which can make the controller select the appropriate control strategy according to different system modal to achieve rapid, stable and precise position-control. The paper has designed fuzzy controller and fuzzy PID controller of position-loop respectively and achieved multi-modal position controller based on fuzzy control and fuzzy PID control with multi-modal control strategy. According to the simulation results of the above controllers, multi-modal controller combines the advantages of fuzzy control and fuzzy PID control, making the system response faster, low-speed oscillation smaller, more accurate, anti-interference stronger, and tracking better.