The nema 17 closed loop stepper motor is an open-loop control element that converts electrical pulse signals into angular or linear displacement. In the case of non-overload, the motor speed, stop position only depends on the frequency and pulse number of pulse signal, and is not affected by load changes, that is, to add a pulse signal to the motor, the motor will turn a step Angle. The closed-loop control of stepper motor is to increase the system complexity and need to find feedback devices, which is equivalent to preventing lost step. Closed-loop stepper motor compensation is generally based on the actual number of pulse received by the driver of upper computer and the error of the corresponding rotation Angle of the actual stepper motor. Generally, the compensation pulse is completed by the closed-loop stepper motor driver.
The closed-loop control of the NEMA 16 stepper motor can be performed using a variety of methods, including step counting (or step checking), sensorless back emf detection, and full servo control with sensor feedback.
Step check is the simplest position control, which uses a low resolution photoelectric encoder to count the number of moving steps. A simple circuit is used to compare the number of instructed steps with the number of measured steps to verify whether the stepper motor has moved to the specified position.
Back electromotive force is a sensorless detection method, which uses the back electromotive force (EMF) signal of a stepping motor to measure and control the speed. When the speed is too low that the back emf voltage is below the detectable level, the closed loop control is switched to open loop control, and then the final positioning motion is completed.
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