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How to add encoder to stepper motor

View:4711/01/2021  

How to add encoder to stepper motor

Does the stepper motor have an encoder

The stepper motor has no encoder. If you want to add an encoder to the stepper motor, you can extend the stepper motor with two shafts and add an encoder on the rear shaft.

The stepper motor is the executive part, and the encoder belongs to the feedback system. The encoder is used in conjunction with the stepper motor, and its operation is controlled by PLC. According to the principle, the PLC sends pulse instructions to the stepper driver, and the driver provides the corresponding current to the stepper motor to make it run. When the encoder detects that the stepper motor runs to the position it needs to reach, it will feedback a signal to the PLC, and the PLC installs The feedback signal stops sending pulse signals to the stepper driver. When the stepper motor has no electric current to provide current, it will of course stop running immediately. (Servo motor is such a device), in fact, the encoder will continuously feedback the current position to the PLC, and the PLC will compare the feedback value with the target value to adjust the rotation angle of the rotor.

Of course, will it stop stably? After stopping, is it the position you want? This depends on whether the motor has a braking device? Of course, at low speeds, the general feed accuracy can be satisfied.

Another is to calculate the number of pulses required for the stepper motor feed in advance, and then use PLC to program, run so many pulses, the stepper motor stops, the encoder feedbacks the motor position at this time, forming a semi-closed loop control. In addition to high-speed positioning, the PLC program can set the motor to decelerate and feed when the position is approaching, which can meet the positioning accuracy.

How to add encoder to stepper motor

The stepper motor encoding is a bit tasteless, it is a waste of resources; because the stepper motor cannot respond in real time, there must be an acceleration and deceleration process;

Example: Use an Oriental stepping motor with a harmonic reducer, a reduction ratio of 100:1, step angle: 0.0072°, want to add an encoder to prevent losing steps, etc., the following is the method:

Answer: In principle, it is also possible to install a motor at one end of the lead screw and an encoder at the other end. However, this will be affected by the accuracy of the reducer, and misjudgment of lost steps may occur. It is best to add an encoder with a double-output shaft motor, and the encoder is added to the back of the motor, and the servo motor does this, unless you are using it for special purposes or conditional restrictions (there is no double-output shaft). Generally, 2500 lines can be processed, and too high number of lines is a waste.

In addition, the resolution of the encoder is approximately the same as the resolution of your stepper motor. If the subdivision on the drive is very high, and you only want to detect whether it is lost, the resolution of the encoder only needs to be the same or slightly higher than the resolution before subdivision.

The meaning of stepping motor plus encoder

Although the stepper motor is a device that can be accurately controlled, it is open-loop, and an encoder needs to be installed to achieve closed-loop feedback control; and the stepper motor's out-of-step and rotation or moving speed can be measured for dynamic speed control. For this statement, the editor feels that the first point of open-loop control requires an encoder to achieve closed-loop feedback is understandable, because the editor himself is in use, occasionally because the wire connection of the stepper motor is not good, resulting in stepping. The motor is not working properly. For the second point, the speed control of the stepper motor is not very necessary, because the speed can be adjusted by controlling the pulse frequency of the stepper motor, and it is really unnecessary to use external feedback.


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