Research On Sensorless Control System Of Stepping Motor Based On Variable Structure Theory

Stepper motors are widely used as the actuator in the field of the industry, residents’life, and high-tech. With the rapid development of science and industrial technology, the stepper motors are required of a higher precision and stability. Due to the problems in the traditional open-loop control of stepper motors limited the application of the stepper motors. The traditional way to ensure the accuracy is to install the encoder. But the encoder makes the system become high costs, less reliability and difficulty in maintenance. According to the problems above, analyzed the advantages and disadvantages of the traditional closed-loop control, this paper proposes an application of sliding mode variable structure control for stepper motor control and the system can avoid the disadvantages by encoder. In this paper, the main research work is done as follows.First, the mathematical model of two-phase hybrid stepper motor and the experiment are made to simulate in open loop control system in Matlab/Simulink. After the experiment, the defects of this system are proposed. According to the problems on control methods, this paper makes a comparison with traditional method with mechanical encode and the method with sensorless base on measurable physical and then chooses a relatively good method with sensorless as the focus of this research. After deeply research and analysis, it is found the method based on Sliding Mode variable Structure Theory is very suitable for the stepper motor which is vulnerable in static and dynamic performance caused by external vibration disturbances and parameter perturbations. In this paper, a sliding mode observer which replaces the traditional mechanical sensors is designed to estimate the position of the rotor.Later, this paper takes the advantage of sliding mode variable structure theory, and then designed a sliding mode controller of the stepper motor together with the sliding mode observer to implement closed-loop sensorless control. The simulation experiment of the closed-loop control system is made in Matlab/Simulink. Experimental results demonstrate the step motor control system can effectively prevent lose step caused by the sudden load changing, improving the dynamic performance of the system and ability to resist disturbance, lower sensitive to motor parameters.Then, this paper establishes the design of hardware and software for controlling the two-phase hybrid stepping motor base on lm3s601. Experimental results show the control system is feasibility and reliability and effectively improve the performance of the stepper motor.Finally, the full paper is summarized, and point out the shortage of this paper and needs to be further improved.