The control method of stepper motor is generally divided into two control methods: open-loop control and closed-loop control. The simplest control method for open-loop control of stepping motor is the Ding-loop control system. In this control mode, the stepping motor controls pulse the input does not depend on the position of the rotor, but instead sends out its control pulses according to a fixed rule. The stepper motor only relies on this series of established pulses to work. This control method is more suitable due to the uniqueness of the stepper motor for controlling stepper motors.

What is a closed-loop stepper motor?

Closed-loop control is a basic concept of cybernetics. Refers to a control relationship in which the controlled output returns to the control input terminal in a certain way and exerts control influence on the input terminal. The closed-loop control of the stepper motor uses position feedback and/or speed feedback to determine the phase conversion adapted to the rotor position, which can greatly improve the performance of the stepper motor.

In a stepping motor system with closed-loop control, the working speed range can be expanded when tracking and feedback with a given accuracy, or the tracking and positioning accuracy can be improved at a given speed, or the limit speed index and limit can be obtained Precision index.

Control method of closed-loop stepper motor

The closed-loop control methods of stepper motors are roughly divided into two types:

1. Keep the phase relationship between the excitation flux and the current consistent, so that it can generate electromagnetic torque that can drive the load torque. This method of controlling the motor current is the same as the brushless DC motor control method, called the brushless drive method or Current closed-loop control method.

2. The motor current is kept constant and the method of controlling the phase angle of the exciting magnetic flux and the current is called the power angle closed-loop control method. The power angle is the phase angle formed by the mutual attraction between the rotor poles and the stator excitation phase (or the axis of the stator rotating magnetic field of a synchronous motor). This power angle is smaller at low speed or light load, and larger at high speed or high load. As shown in the following figure in the principle of open-loop control in the previous article, the "bar A" phase attracts the rotor pole, and the angle of the "bar B" phase is π/2 when the phase is excited, and the rotor pole is located at the leading edge of the "bar A" phase ( When the S pole of the rotor is located on the left side of phase A), the magnetic pole "bar B" phase starts to be excited.