1. Definition of bipolar stepper motors
A bipolar stepper motor is a motor that converts electrical pulse signals into precise angular or linear displacements. ‌It contains two main coils, each with two wires, a total of four wires, which are used to control the rotation of the motor. When an appropriate current pulse is applied to the coil of a bipolar stepper motor, it rotates according to a preset step angle. By precisely controlling the sequence and frequency of the current pulses applied to each coil, the direction and speed of the motor's rotation can be precisely controlled. ‌

2. Main features of bipolar stepper motors
1‌. High-precision positioning‌: Due to the use of stepping technology, bipolar stepper motors can accurately position to the required position, and each step position is very accurate, meeting the needs of high-precision control‌. ‌2. Strong reversibility‌: By changing the direction of the external current, the bipolar stepper motor can achieve forward and reverse rotation, adapting to various complex motion control needs‌. ‌ ‌3. Large static torque‌: Even in a stationary state, bipolar stepper motors can provide high torque output, can withstand various loads, and provide good starting power when they start to rotate.
4. Flexible control method‌: Because it contains two coils and four wires inside, bipolar stepper motors are more flexible in control method than unipolar stepper motors and can adapt to a wider range of control strategies and application scenarios.
5. Sensitive dynamic response‌: Bipolar stepper motors have a faster dynamic response speed and can quickly adjust the control amount to cope with system changes.

3. High-precision positioning method of bipolar stepper motors
1. Full step control‌: This is the simplest control method, driving the motor a full step angle each time. By controlling the on-off sequence of the current, ensure that the motor switches between each orthogonal position. The implementation steps of full step control include initializing the port of the stepper motor, setting the current sequence, and cyclically outputting the control signal to make the motor rotate step by step.
2. Half step control‌: By changing the phase of the current, the motor rotates half a step angle each time. This method can improve positioning accuracy because each rotation is smaller, reducing the cumulative error.
‌3. Microstepping control: By finely controlling the phase and duration of the current, the motor can make smaller rotations within each step angle, further improving positioning accuracy. Microstepping control requires more complex circuits and higher control accuracy.
‌4. Dynamic control algorithm: It includes acceleration and deceleration control and position feedback control. Acceleration and deceleration control improves positioning accuracy by smoothly changing the speed of the motor and reducing the impact during starting and stopping. Position feedback control monitors the actual position of the motor in real time through feedback devices such as encoders, and adjusts the control signal according to the deviation to achieve closed-loop control.
‌5. Subdivision drive: Set the subdivision parameters in the driver to subdivide a step angle into smaller microsteps. This can improve the accuracy of position control and reduce positioning errors.
‌6. Closed-loop feedback system: Use feedback devices such as encoders to feed back the actual position information of the motor to the control system. The control system adjusts the pulse signal according to the deviation between the feedback information and the target position to achieve closed-loop position control.
‌7. Speed ​​control‌: In the process of position control, combined with speed control, the frequency of the pulse signal is adjusted to change the speed of the motor, so that a smooth stop is achieved when the target position is reached‌.

4. Common applications of bipolar stepper motors
‌1. CNC machine tools‌: Bipolar stepper motors are widely used in CNC machine tools because they can directly convert digital pulse signals into angular displacement without A/D conversion, which makes them excellent in positioning control. CNC machine tools require high-precision position control, and stepper motors just meet this need‌.
‌2. Printers‌: In printers, bipolar stepper motors are used to move the print head position and feed the printing paper. By precisely controlling the movement of the stepper motor, the quality and accuracy of the printed output can be ensured‌.
‌3. Digital cameras‌: Stepper motors control the lens in digital cameras to adjust the focal length and brightness of the subject. This application requires stepper motors with high-precision position control and stable performance‌.
‌4. Air conditioners‌: In air conditioning systems, bipolar stepper motors are used to move the shutters of indoor units, thereby changing the direction of airflow. By precisely controlling the movement of the shutters, more efficient airflow regulation can be achieved.
‌5. Slot machines: Stepper motors turn the scroll in the slot machine and stop it precisely at the specified position. This application requires the stepper motor to have high-precision position control and stable stopping capabilities.
‌6. Astronomical telescopes: Stepper motors are used in accessories of astronomical telescopes to automatically search and track stars located by a controller or computer. This application requires stepper motors to have high-precision position control and stable motion performance.
‌7. Laser engravers, 3D printers, and laser printers: Bipolar stepper motors are often used in these small industrial machines because they are cost-effective, easy to drive, and suitable for open-loop systems. The open-loop control characteristics of stepper motors enable these devices to achieve high-precision positioning and motion control.

Source:https://blog.udn.com/stepperrelation/182285465