The working principle of stepper motor
Stepper motor is a kind of control motor that converts electrical pulse signal into mechanical angular displacement. The so-called electric pulse, similar to pulse, is felt when the pulse beats similar to the high level of the pulse, and low level when it doesn't. This is the electric pulse signal. The unit of angular displacement is radian.
Stepper motor can be divided into reactive, permanent magnet type, hybrid type. Each has its own advantages, choose according to the actual needs, reactive type has small step angle and high precision; permanent magnet type has large torque. The hybrid type has high precision and high torque, but high cost. The following is an example of the structure and working principle of stepper motor with reactive type. A stepper motor consists of two main parts:
Stator and Rotor. The stator and rotor are not unfamiliar after learning about DC motors. However, stepper motors, for example, have six and four magnetic poles on the stator and rotor, respectively. In the above figure, A and A form one phase; B and B are one phase; C and C are one phase. So this stepper motor is a three-phase stepper motor.
Stepper motor receives an electrical pulse signal, it will correspondingly rotate a fixed angle, this fixed angle, is one of the important parameters of stepper motor, step angle. In detail, when the stepper motor receives an electrical pulse signal, phase A is energized and the magnetic flux in the direction of A forms a closed loop through the rotor. If the rotor and the direction of the magnetic field axis is originally at a certain angle, the rotor is magnetized under the action of the magnetic field, which attracts the rotor and causes the teeth of the rotor and stator to align and stop rotating. That is, phase A is energized to align rotor 1 and 3 teeth with AA'; the next pulse signal comes, phase B is energized to align rotor 2 and 4 teeth with BB; the third pulse signal comes, phase C is energized to align rotor 3 and 1 teeth with CC'. This drive method is the three-phase three-beat drive method.
Therefore, the stepper motor is dependent on the number of pulses to rotate, and the number of pulses is given to the corresponding number of revolutions. Therefore, the stepper motor can achieve the purpose of accurate positioning; at the same time, it can control the speed and acceleration of motor rotation by controlling the pulse frequency, that is, controlling how long to give a pulse, so as to achieve the purpose of speed regulation. Every time an electrical pulse is input, the motor rotates an angle one step forward. The angular displacement of its output is proportional to the number of pulses input, and the speed is proportional to the pulse frequency. Change the order of winding energization to control the motor forward and reverse rotation. That is, if the sequence of energizing A, B and C phases is positive, then the motor will be reversed if the sequence of energizing C, B and A phases is followed. So you can control the number of pulses, frequency and the order of energizing each phase of the motor winding to control the rotation of the stepper motor.