Open loop and close loop of stepper motor
Stepping motor control mode is generally divided into open-loop control and closed-loop control, and the most simple control mode of open-loop control stepper motor is Ding ring control system,under this control mode,the stepper motor pulse input control does not depend on the position of the rotor, but according to a fixed law to issue control pulses, stepper motor only rely on this series of established pulse to work,this control mode because of the unique characteristics of stepper motor is more suitable to control stepper motor,this control methods that is suitable for China's national conditions is characterized by simple control, easy to implement, low price.This control mode, especially in open-loop control, the load position do not feedback to control.
Therefore,the stepper motor must respond to the change of each excitation.If the excitation changes too fast,then motor can not move to new position, the actual load position and the ideal position will produce a deviation. When the load is basically constant,the control pulse sequence generation is relatively simple, but under the load changing larger occasions,the control pulse sequence is difficult to take care of the whole,there may be stepper lost and other phenomena.With the application of microcomputer at current,relying on microcomputer,it is possible to realize the generation of control pulse sequences of some more complicated stepping motors.
However,this control method also has the following shortcomings: the motor output torque and speed not only has a great relationship with load,also depends on the drive power and control realization way at large extent,the accuracy is not high,and sometimes there will be step lost,oscillation and other phenomena, but because it is easier to achieve, low prices, so majority current control mode are open-loop control.Closed-loop control,as the stepper motor open-loop control system is not high precision,step lost and other shortcomings,so the high precision requirements occasion can use stepper motor closed-loop control system.
The reactive stepper motor specializes in the closed-loop control principle, which directly or indirectly detects the position or velocity of the rotor (or load),and then after feedback and proper processing,automatically gives hybrid servo motor driving pulse sequence,the driving pulse sequence is based on the load or the position of the rotor to change at any time .Closed loop control mode,combined with micro-step drive technology and microcomputer control technology, can be achieved very high position accuracy requirements to satisfy high precision occasion.