The Design Of Three-Phase Hybrid Stepper Motor Drive Based On The Fuzzy-PI Control Method

As a special motor, stepper motor’s control signal is the pulse wave. As it can achieve higher precision of movement under the open-loop control, stepper motor is widely used in the occasions which are low power or there are certain requirements about precision of movement. As people wanting to have higher precision of movement, stepper motor could not reach that requirement when it is controlled under the open-loop. At the same time, the inherent shortcomings of the stepper motor, including oscillation under the low-frequency, desynchronization under the high frequency are still serious. If we can optimize the motion characteristics of the stepper motor, as well as improving the accuracy of its motion, while improving its inherent shortcomings, it will make the stepper motor be used in wide range of applications.In this paper, we will make research of the three-phase hybrid stepper motor. In response to the above request, we consider the use of closed-loop control to improve the accuracy of its motion. Because the conventional PI control demonstrating poor adaptability when it is used to control stepper motor which is containing varying nonlinear parameters, this paper introduces the fuzzy PI control method to make the control system be able to control the stepper motor better as well as achieving higher motion accuracy by online adjustment of PI control proportional coefficient Kp and integral coefficient Ki through the fuzzy theory. The main work of this paper is as follows:1. By elaborating the mechanical structure, movement characteristics, basic work of the three-phase hybrid stepper motor, this paper analyzes its reasons that why there are a oscillation under low-frequency, and desynchronization under the high frequency. Establish approximate mathematical model combined with the structure characteristics of the three-phase hybrid stepper motor, providing certain reference significance for subsequent analysis.2. Establish the feedback control system of stepper motor which is based on the phase current. For the mathematical model of the three-phase hybrid stepping motor has complex nonlinear, time-varying parameters, the conventional PI control method being difficult to achieve high precision, fuzzy theory is proposed to online adjusting its main control parameters Kp, Ki, so that the control system is able to make the electromagnetic torque of the stepper motor have a better track on the change of the load. So as to achieve higher motion accuracy, at the same time running more smoothly. Subsequently, introducing the design of the control system and making simulation, to verify the control effect.3. Combined with the above theoretical analysis, this paper designs the drive of the three-phase hybrid stepping motor. Introduce its hardware design, as well as the framework of the software and the main program.