I. What is a stepper motor?
A stepper motor is an electromechanical device that directly converts electrical pulses into mechanical motion. By controlling the sequence, frequency, and number of electrical pulses applied to the motor coils, the direction, speed, and rotation angle of the stepper motor can be controlled. Precise position and speed control can be achieved using a simple and low-cost open-loop control system composed of a stepper motor and its matching driver, without relying on a closed-loop feedback control system with position sensing.
II. Characteristics of Mingzhi Stepper Motors
Precise position control determines the axis rotation angle based on the number of input pulses. Position errors are extremely small (less than 1/10 degree) and do not accumulate.
Precise speed control of stepper motors depends on the frequency of the input electrical pulses, enabling precise control and easy adjustment. Therefore, they are widely used in various motion control fields.
Forward/reverse rotation, emergency stop, and locking functions enable effective control of motor torque and position, including static torque, across the entire speed range. Even in the motor locked state (where current flows through the motor windings but there is no external pulse command input for rotation), a certain torque output is still maintained.
Precise positioning control stepper motors under low speed conditions can operate smoothly at very low speeds without the need for gearbox adjustment, while outputting large torque, avoiding power loss and angular position deviation, and reducing costs and saving space.
The brushless design of stepper motors ensures a long service life. The lifespan of a stepper motor typically depends on its bearings.
III. Basic Structure and Working Principle
Basic structure:
Working principle:
The stepper motor driver, based on external control pulses and direction signals, uses its internal logic circuitry to control the stepper motor windings to be energized in a specific timing sequence in the forward or reverse direction, causing the motor to rotate in the forward/reverse direction or lock.
Taking a 1.8 -degree two-phase stepper motor as an example: When both phase windings are energized, the motor output shaft will remain stationary and locked in position. The maximum torque required to keep the motor locked under rated current is the holding torque. If the current in one phase winding changes direction, the motor will rotate one step ( 1.8 degrees) in a predetermined direction.
Similarly, if the current in another winding changes direction, the motor will rotate one step ( 1.8 degrees) in the opposite direction. When the current through the coil windings is sequentially reversed to excite the motor, the motor will continuously rotate in a predetermined direction with very high precision. A 1.8 -degree two-phase stepper motor requires 200 steps to complete one revolution.
Two-phase stepper motors have two winding configurations: bipolar and unipolar. A bipolar motor has only one winding coil per phase. As the motor rotates continuously, the current must sequentially change direction within the same coil for excitation. The drive circuit design requires eight electronic switches for sequential switching.
A unipolar motor has two winding coils with opposite polarities on each phase. When the motor rotates continuously, it only requires alternating energization of the two winding coils on the same phase. The drive circuit design requires only four electronic switches. In bipolar drive mode, because the winding coils of each phase are 100% energized, the output torque of the motor in bipolar drive mode is increased by approximately 40% compared to unipolar drive mode.
(To be continued...)
Mingzhi is a professional company specializing in high-precision and cost-effective motion control products. Our products include stepper and servo motors, drivers, and linear modules. Our standardized and customized products serve users and equipment manufacturers across various industries. With in-depth motor development and professional control technology, Mingzhi provides you with the best motion control solutions.
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