A stepping motor (also called a stepping motor) is a stepping motor that rotates in an intermittent manner, stepping at a fixed angle for each step, rather than continuously rotating its shaft.
For example, the movement of the second hand on the clock (for example, moving forward one second per second) can be achieved by using a stepper motor to move in 6° increments per second.
So, how does a stepper motor realize the characteristic of rotating its axis at a fixed angle in each step?
The secret lies in the use of electrical pulses. A pulse is an electrical signal generated by turning the power on and off, and each such switch counts as a pulse. The stepper motor uses these pulses to achieve precise mechanical control of the rotation angle and rotation speed.
Types of stepper motors 
The rotor structure of a stepper motor can be roughly divided into the following three categories.
Permanent magnet (PM) motor
The rotor contains a permanent magnet. The disadvantage of this structure is that it cannot provide flexibility in the rotation angle (step angle).
Variable Reluctance (VR) Motor
The rotor contains an iron core with a structure similar to gear teeth. This provides greater flexibility in setting the step angle.
Hybrid (HB) motor
The rotor contains permanent magnets and an iron core with a structure similar to gear teeth. Combining the advantages of PM and VR motors, this type of motor is widely used in various applications. All stepping motors developed and manufactured by ASPINA are HB motors.
The working principle of HB stepper motor
The design of the rotor is to place a cylindrical permanent magnet between two iron cores. The two iron cores are concentric with the motor shaft and offset from each other by half a pitch. Each time a pulse is input, the rotor will rotate by a fixed step angle. Since the two-phase HB stepper motor with a step angle of 1.8° rotates 1.8° per pulse, it takes 360°/1.8°=200 pulses to rotate a full circle.
Type of stepper motor 
The current in a unipolar motor always flows through the coil windings in the same direction. Although this keeps the associated control circuit simple, it produces less torque than a bipolar motor.
The current in a bipolar motor can flow through the coil windings in either direction. Although this requires a more complex control circuit compared to a unipolar motor, it produces a greater torque.
Features of stepper motors
Stepper motors are different from other motor types in the following aspects.
Since the rotation angle is determined by the number of pulses (digital input), the position control (rotation angle) is very simple
Can rotate at low speed
Can use open loop (non-feedback) position control
Excellent ability to maintain the locked position when stopped
Need drive circuit
Due to unexpected changes in load and other factors, synchronization may be lost
High level of vibration and noise