What is a Closed-loop Stepper Motor?

The so-called closed-loop stepper motor is the additional encoder of the stepper motor to realize the high precision and low jitter function of the servo motor, so it is called the closed-loop stepper motor.

In most cases, the stepper motor is open-loop nature, that is, the motor accepts the control instructions of the PLC through the bus or other means, and does not carry out motion feedback. In this way, the structure of the entire motor system can be simpler and the cost can be lower. Compared with the open-loop control stepper motor, the closed-loop stepper motor is to add an encoder structure to the motor, so that it becomes a servo system. The motor receives the driver pulse at the same time, but also feedback the pulse to the driver and even the PLC, to achieve the control of the question and answer, and the reliability is higher. Of course, because of the increased structure, the cost of the motor is higher, and it is suitable for projects with relatively high control requirements.

Functional characteristics of closed-loop stepper motor

1. Compared with the traditional stepping products, the closed-loop stepper motor will not lose steps, which can ensure the precise positioning of the motor, reduce the vibration of the motor, make the operation more stable, and save power consumption by the variable current control technology.

2. Compared with traditional AC servo products, closed-loop stepper motor does not need complex parameter adjustment, it is more convenient to use, does not jitter when stopping at high speed, stops at zero speed and is stable, position response is extremely fast, especially suitable for short distance fast start and stop occasions, with larger torque and smaller installation size.

3. Because of the closed-loop control technology, it does not lose step like the AC servo system. The position encoder is installed to make the motor have the closed-loop characteristics of the servo motor, and fundamentally solve the problem of losing step of the traditional stepper motor.

4. Greatly improve the high-speed performance of the motor and can increase the motor torque.

5. Effectively reduce the motor heat.  

6. Shorten the corresponding time of motor acceleration and deceleration. The output and input instructions of the position response are almost real-time synchronization, so it is very suitable for short distance fast start and stop and zero speed steady stop occasions. There is no oscillation when the motor brakes. The closed-loop stepper servo drive system has the unique torque-holding characteristics of stepper motors, and can reach the set position stably without oscillating.

7. Closed-loop stepper motor runs more smoothly and has higher accuracy. The most advanced special motor control DSP chip is used to realize the smooth motion control of the stepper motor by vector control and smoothing filter technology.

8. No gain adjustment, very easy to use. The closed-loop stepper servo system has the dual advantages of convenience of stepper motor and reliability of servo system, and can be used easily without complicated parameter debugging.

So can the closed-loop motor completely replace the servo motor?

The answer is no, the stepper motor with encoder just to achieve most of the performance of the servo motor, can only say that the servo motor within 3000 RPM can be replaced by the closed-loop motor, if the speed is too high, it is recommended that you choose the servo motor. After all, the stepper motor can not break through in terms of high speed. However, if you refer to the price-performance ratio, you can choose to add an encoder.

The performance of the stepper motor equipped with the encoder can be improved in the following four ways.

1, improve the control accuracy of the stepper motor;

2. Solve the step loss problem of stepping uncertainty;

3, improve the heating problem of the stepper motor;

4, solve the servo control system in the zero jitter problem.

The so-called closed-loop stepper motor is the additional encoder of the stepper motor to realize the high precision and low jitter function of the servo motor, so it is called the closed-loop stepper motor.

In most cases, the stepper motor is open-loop nature, that is, the motor accepts the control instructions of the PLC through the bus or other means, and does not carry out motion feedback. In this way, the structure of the entire motor system can be simpler and the cost can be lower. Compared with the open-loop control stepper motor, the closed-loop stepper motor is to add an encoder structure to the motor, so that it becomes a servo system. The motor receives the driver pulse at the same time, but also feedback the pulse to the driver and even the PLC, to achieve the control of the question and answer, and the reliability is higher. Of course, because of the increased structure, the cost of the motor is higher, and it is suitable for projects with relatively high control requirements.

Article source: https://article-realm.com/article/Product-Reviews/48297-What-is-a-Closed-loop-Stepper-Motor.html