Stepper motors usually drive loads in an open-loop manner, but under this condition, the command and actual step are easily out of step, which leads to "sequelae" and stalling is also an unavoidable problem of stepper motors.
At present, the closed-loop/servo controller driven by stepper motor has been sought after by people in the industry. Closed-loop controller has become the best alternative to high-cost servo motors because of its advantages of improving stepper motor performance, increasing speed and checking out out of step.
So how to better apply closed-loop controller in stepping control system? It is suggested to operate by adding control function and changing performance while keeping its original operation mode unchanged.
Firstly, two different ways of installing additional controllers are introduced.
(1) Installing rotary incremental encoder in motor is a typical stepping motor servo function; (2) Installing rotary encoder or linear moving grating ruler at the end of transmission device is a terminal position servo function, i.e. terminal closed loop, which can be used as grating ruler digital display. Its advantage is to eliminate backlash errors in mechanical transmission. Poor;
Secondly, it can effectively solve the defects of stepper motor such as high-speed stall, overload stall and overshoot, and overload stall protection. It can also raise the original maximum speed of ordinary stepper motor from 300 rpm to 1000 rpm. It is not necessary to only lose step and stall, but also overload stall occurs during operation. The controller will automatically reduce the speed. If it fails, it protects the downtime and gives an alarm. After the failure is solved, it can continue to run to the designated location without relocation.
Thirdly, the accuracy of stepper motor is completely determined by encoder or grating ruler, so its positioning accuracy is changed from the original stepper motor driver subdivision calculation to the number of coder lines subdivision calculation, such as: the number of coder lines is 2500 lines, through the controller 4 times frequency, that is, 2,500X4 = 10,000, its subdivision is 10,000 pulse stepper electro-rotation cycle. The stepping angle is 0.036 degrees.
Finally, the closed-loop function of the in-place signal feedback system is added: the controller synchronously feeds back the position information and fault information of the stepper motor to the upper computer in real time. The controller receives the pulse control signal of the designated position from the upper computer, and synchronously sends out the pulse control step drive. During the operation, the controller feedback is running the information control. The signal is sent to the host computer, after confirming the designated position, the information is sent back to the host computer to complete a positioning instruction cycle and continue the next positioning instruction cycle.