First. Introduction
In the modern industrial control field, stepper motors are favored for their unique stepping characteristics and precise position control. Among them, bipolar stepping motor, as an important type of stepping motor, is widely used in many fields such as automated production lines, precision measuring instruments and so on by virtue of its high efficiency and reliable performance. In this paper, the structure and control modes of bipolar stepping motors will be introduced in detail, aiming to provide readers with an in-depth understanding and knowledge.
Second, the structure of bipolar stepper motor
Bipolar stepping motor, also known as two-phase four-wire stepping motor, its basic structure includes the stator, rotor and winding three major parts.
Stator
The stator is the stationary part of a bipolar stepper motor, usually composed of several stator teeth. In a bipolar stepper motor, the stator teeth are wound with two-phase bipolar windings, i.e., A-phase and B-phase windings. Each of these two phase windings consists of a different coil, each with two wires, for a total of four wires, which are used to control the operation of the motor.
Specifically, the A-phase winding is wound from stator tooth 1, and is wound sequentially to stator teeth 3, 5 and 7, where stator teeth 1 and 5 are wound in the same direction, while stator teeth 3 and 7 are wound in the same direction. These two groups (stator teeth 1 and 5, and stator teeth 3 and 7) are wound in opposite directions.The B-phase windings are wound on the same principle, with stator teeth 4 and 8 as a group and stator teeth 2 and 6 as a group.
Rotor
The rotor is the rotating part of a bipolar stepper motor and is usually affixed with axially magnetized permanent magnets. The magnetic lines of force of the permanent magnets form a closure within the body of the motor, allowing the rotor to have a locking torque even when not energized. In addition, the rotor usually possesses a number of teeth (e.g., 50 teeth) that correspond to the stator teeth for precise stepping angles (e.g., 1.8° stepping angle).
Windings
The winding of a bipolar stepper motor is the key part of the motor that realizes the motion of the motor. Since bipolar stepper motors have two separate coils, each of which can be energized in both directions, one end of each winding can be either an N or S pole. This design makes the bipolar stepper motor more flexible in the control mode, which can realize more accurate position control and higher dynamic performance.
Third, the control mode of bipolar stepper motor
The control modes of bipolar stepper motor mainly include single-phase stepping, whole-step stepping and half-step stepping.
Single-phase stepping
Single-phase stepping is the most basic control mode of bipolar stepping motor. In this mode, the A-phase and B-phase windings are energized sequentially in a certain order, causing the stator magnetic field to change accordingly, thus driving the rotor to rotate. Specifically, when the A-phase winding is energized, the rotor will rotate in one direction; when the B-phase winding is energized, the rotor will rotate in the other direction. By alternately controlling the energized state of the A-phase and B-phase windings, continuous rotation of the rotor can be achieved.
The single-phase stepping mode is simple and easy to understand, but because of its large stepping angle (usually 1.8°), it may not be adequate in applications where higher precision control is required.
Whole-step stepping
Whole-step stepping is one of the more commonly used control modes for bipolar stepper motors. In this mode, the A-phase and B-phase windings are energized or de-energized at the same time to achieve a full-step rotation of the rotor. Specifically, when the A-phase winding is energized and the B-phase winding is de-energized, the rotor will rotate in one direction by a certain angle; when the B-phase winding is energized and the A-phase winding is de-energized, the rotor will rotate in the other direction by the same angle. By alternately controlling the energized state of the A-phase and B-phase windings, continuous whole-step rotation of the rotor can be realized.
The whole-step stepping mode has the advantages of small stepping angle and high positioning accuracy, so it is widely used in applications requiring high-precision control. For example, in office equipment such as printers and scanners, bipolar stepper motors usually use the whole-step mode to control the precise movement of the print head or scan head.
Half-step
Half-step is a more refined mode of control for bipolar stepper motors. In this mode, half-step rotation of the rotor can be achieved by simultaneously controlling a portion of the coils in the A-phase and B-phase windings to be energized or de-energized. Specifically, when a part of the coil in the A-phase winding is energized and a part of the coil in the B-phase winding is de-energized, the rotor will rotate by half a step in one direction; when a part of the coil in the B-phase winding is energized and a part of the coil in the A-phase winding is de-energized, the rotor will rotate by half a step in the other direction. By alternately controlling the energized state of the coils in the A-phase and B-phase windings, continuous half-step rotation of the rotor can be realized.
The half-step mode has the advantages of a smaller step angle and higher positioning accuracy, and is therefore widely used in applications requiring higher precision control. For example, in the field of precision measuring instruments, medical equipment, etc., bipolar stepping motors usually use half-step mode to realize more accurate position control and motion control.
Fourth, summary
Bipolar stepper motors play an important role in the field of industrial automation control with their unique structure and control mode. Through in-depth understanding of the structure and control mode of bipolar stepper motors, we can better master its application methods and techniques, and provide strong support for the development and application of industrial automation control technology.