Design And Implementation Of High Performance Closed-loop Drive System For Stepper Motor Under Nonlinear Load

The stepper motor has been widely used in industry because of its characteristics of simple control mode and high torque at medium and low speed.With the application of intelligent manufacturing technology,stepper motors are used for positioning in many cases such as factory automation and mechatronics equipment.Stepper motor is controlled in open-loop methods generally,which mainly has shortcomings such as easy step-out in load mutation,poor ability to adapt to the load,poor dynamic performance during operation.So it's difficult to apply open-loop methods to high-performance situation.With the development of digital control technology and the improvement of microprocessor capability,the application of new control algorithms in speed control and position control of stepper motors has become possible.Therefore,the research of high-performance stepper motor drive is of great theoretical and practical engineering significance.Two-phase hybrid stepper motor is taken as the research object.Firstly,the load situation of the application is analyzed and the problems of the traditional control mode in this situation are analyzed.Then the closed-loop field-oriented control(FOC)for the problem is proposed to realize a closed-loop drive control system of stepper motor with high dynamic performance,high speed operation capability,strong load capacity,and it improves the traditional open-loop control mode with step-out,poor controllability,high running noise,poor dynamic response,poor algorithm robustness and other issues.The main research contents of this paper are as follows:(1)The load situation of the application scenario and the characteristics of the stepper motor are analyzed in detail.The theoretical model of the load and the two-phase hybrid stepper motor is established.And the model is used to analyze the problems in the traditional control method,and we propose a solution to the problems--the application of FOC to the stepper motor to meet the requirements of high dynamic characteristics,fast response and high position control accuracy in application scenarios.(2)According to the characteristics of two-phase hybrid stepper motor,SVPWM of two phases is designed and FOC is advanced.Based on which the field-weakening control is designed to improve the speed range of stepper motor.The position closed-loop control algorithm based on load torque observer is designed to reach fast response and precise positioning under non-linear loads.Acceleration curve is optimized to reduce jitter when starting and stopping.Based on the application object model and algorithm,the simulation is implemented by MATLAB to verify the effectiveness of the algorithm.(3)The hardware circuit based on DSP of the closed-loop drive control system is designed.The high-performance closed-loop drive system for stepper motor is developed,which realizes FOC,field weakening control and position closed-loop control.A test platform is set up in order to test the dynamic performance,speed,position control accuracy,etc.,of the closed-loop drive control system.Traditional open-loop control method is compared as well.The solution proposed is applied to the nonlinear load situation eventually.Experimental results show that the closed-loop control system of the stepper motor has better performance than the traditional open-loop control method.The acceleration can reach 50 rpm/ms or more(24V),and the maximum speed can be increased by more than 50%,and the system can be applied to the high-performance situation.