I. Main Structure of a Stepper Motor
Stepper motors are limited by their manufacturing process. For example, the step angle is determined by the number of rotor teeth and the number of cycles, but these are finite. Therefore, the step angle of a stepper motor is generally large and fixed. Stepping also results in low resolution, lack of flexibility, vibration at low frequencies, and higher noise levels than other micromotors, making the device prone to fatigue or damage. These drawbacks limit stepper motor applications to less demanding situations. For more demanding applications, closed-loop control is necessary, increasing system complexity. These limitations severely restrict the effective use of stepper motors as excellent open-loop control components. Microstepping technology effectively overcomes these drawbacks to some extent.
Stepper motor microstepping technology, developed in the mid-1990s, is a driving technology that significantly improves the overall performance of stepper motors. In 1998, American scholars first proposed the step angle microstepping control method for stepper motors at the American Conference on Incremental Motion Control Systems and Devices. Over the following two decades, stepper motor microstepping technology saw significant development, gradually maturing by the 1990s. Research on microstepping technology in my country started at roughly the same time as in other countries.
Significant development occurred in the mid-1990s. Its main applications are in industry, aerospace, robotics, and precision measurement, such as photoelectric theodolites for tracking satellites, military instruments, communication and radar equipment. The widespread application of microstepping technology has made the number of phases of the motor no longer limited by the step angle, facilitating product design. Currently, microstepping technology for stepper motors employs chopper constant current drive, pulse width modulation drive, and current vector constant amplitude uniform rotation drive control, greatly improving the operating accuracy of stepper motors and enabling stepper motors to develop towards high speed and precision in medium and low power applications.
II. Differences between reactive stepper motors and permanent magnet stepper motors
Reactive stepper motors and permanent magnet stepper motors are both common types of stepper motors. The main difference between them lies in their working principle and structure.
A reactive stepper motor utilizes the principle of an asynchronous motor, dividing the stator windings into two or more windings and using electronic devices (such as thyristors) to control the magnetic flux generated on the rotor, thereby achieving stepping motion. The advantages of reactive stepper motors are long service life and good controllability; the disadvantages are a smaller step angle and poorer torque stability.
Reactive stepper motors use an external alternating power supply to generate a magnetic field, which causes the rotor to rotate. This type of stepper motor requires fewer components, resulting in a simple structure and lower cost. However, because reactive stepper motors rely on alternating power supplies to generate the magnetic field, instability and noise issues may occur during low-speed operation.
Permanent magnet stepper motors use a fixed permanent magnet field to drive the rotor, thus requiring no external power supply. This type of stepper motor typically offers higher precision and better control performance, making it more common in certain specialized applications. However, permanent magnet stepper motors are generally more expensive because they require more components to control the magnetic field.
Permanent magnet stepper motors utilize the magnetic force between a permanent magnet and the stator windings to achieve stepping motion. Under pulse control, each pulse causes the permanent magnet to move at a specific step angle. The advantages of permanent magnet stepper motors are a larger step angle and better torque stability, but their disadvantage is that they are difficult to control.
Overall, both types of stepper motors have their own advantages and disadvantages, and the appropriate type should be selected based on the specific application scenario.
