Closed loop stepper motor is a product between the stepper motor and AC servo motor, similar to an SUV between a car and an off-road vehicle, which not only meets the comfort but also has a certain off-road ability.
Closed loop stepper motors are divided into Nema 17, Nema 23, Mema 34 according to their flanged size. And they are also divided into step type closed loop stepper motor system and servo type closed loop stepper motor system.
Step type closed-loop stepper motor system refers to adding a low-precision encoder to the original stepper motor, and simply adding the encoder reading circuit as the position correction based on the original driver, and only comparing the command position and feedback position when stopping. Motor speed, output torque, and traditional stepper motor have no difference. Servo type closed-loop stepper motor system: refers to the use of servo motor control technology, stepper motor position and speed, and output torque are real-time adjustment, according to the real, strict servo control principle, position deviation, current, speed PID adjustment. The speed and output torque of the motor is better than the traditional stepping motor.
So what are the advantages of closed loop stepper motors?
The traditional stepper motor uses the simplest constant current control, so the control cycle of the current loop is too long, so the speed is generally below 1000rpm; while the closed loop stepper motor uses the principle of servo driver, the current of the stepper motor is controlled by vector mode, and the maximum speed can reach 3000rpm. In the speed range of 0 ~ 1500rpm, the output torque is larger than that of an ordinary step. The output torque of the motor is large. Based on the above reasons, if the stepper motor has higher speed requirements, the closed-loop stepper motor is the only choice.
The accuracy of the traditional stepper motor is determined by the number of phases and driver subdivision. For example, the accuracy of the 5-phase motor is greater than the 3-phase, and 3-phase is greater than the 2-phase; the precision of the high subdivision driver is higher than that of the low subdivision driver. However, due to the cascade control of current, the improvement of accuracy is not only limited but also has only resolution and no precision in the high subdivision. The precision of the closed loop stepper motor does not depend on the phase number of the motor but on the encoder accuracy of the motor. At present, due to the technical limitation, domestic manufacturers can only provide 1000 line encoder as standard, while ATO motor can directly configure 2500 line motor as standard, which can directly reach the standard precision of servo motor. Based on the above reasons, if the stepper motor has higher accuracy requirements, the closed-loop stepper motor is the top choice.