Closed loop stepper motor control method
The closed-loop control of stepper motors is roughly divided into two types:
1. The phase relationship between the excitation magnetic flux and the current is kept consistent, so that the electromagnetic torque capable of driving the load torque is generated. The method for controlling the motor current is the same as that of the brushless DC motor, and is called a brushless driving method or Current closed loop control method.
2. The motor current is kept constant, and the way of controlling the phase flux of the excitation flux and current is called the power angle closed-loop control method. The power angle is the phase angle at which the rotor pole and the stator excitation phase (or the stator rotating magnetic field axis of the synchronous machine are also considered to be attracted). This power angle is small at low speeds or at light loads, and is large at high speeds or high loads. Referring to the lower part of the principle part of the open-loop control mentioned above, the “bar A” phase attracts the rotor pole, and the second “bar B” phase has an angle of π/2, and the rotor pole is located at the front edge of the “bar A” phase ( When the S pole of the rotor is located on the left side of the A phase, the magnetic pole "bar B" phase is excited.
why? Because of the influence of the inductance of the coil, the turn-off time of the A-phase current is prolonged, and the rise time of the B-phase current is also prolonged. Therefore, the angle at which the maximum torque is accelerated is increased, and the value becomes larger as the speed becomes faster.
Closed-loop stepper motor working principle diagram
This control method directly or indirectly detects the position or speed of the transfer (or load), and then automatically gives the drive pulse sequence of the stepper motor through feedback and appropriate processing. This drive pulse sequence is based on the load or There are many ways to control the position of the rotor and change it at any time. In the case of high precision, combined with micro-step drive technology and microcomputer control technology, high positional accuracy can be achieved.
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