Hello everyone, today we will talk about itservo motor The difference between stepper motors. Servo motors and stepper motors are commonly used types of motors, which have different advantages and disadvantages in terms of control methods, performance characteristics, and application scenarios. Below, I will introduce them one by one for everyone.

Construction and driving principle of motor

There are the following differences in construction and driving principles between servo motors and stepper motors:

Servo motor: A servo motor is a type of motor that uses an encoder to feedback the position and speed of the motor, and achieves high precision and high response through closed-loop control. The internal rotor of the servo motor is a permanent magnet, and the external stator is a three-phase winding. The magnitude and phase of the three-phase AC power are controlled by the driver to form a rotating magnetic field, which drives the rotor to rotate. At the same time, the encoder sends the angle and speed information of the rotor to the driver. The driver adjusts the amplitude and frequency of the current based on the difference between the feedback signal and the command signal, so that the rotor reaches the target position and speed.

Stepper motor: A stepper motor is a type of motor that uses pulse signals to control the step angle of the motor and achieves positioning operation through open-loop control. The internal rotor of a stepper motor is also a permanent magnet, and the external stator is a multi-phase winding. The on/off of multi-phase DC power is controlled by a driver to form magnetic poles that attract or repel the magnetic poles of the rotor, causing the rotor to rotate at a fixed angle (step angle). Every time a pulse signal is received, the rotor rotates by a step angle. By controlling the number and frequency of pulses, the position and speed of the rotor can be controlled.

Performance characteristics of motors

There are the following differences in performance characteristics between servo motors and stepper motors:

Control accuracy: The control accuracy of servo motors depends on the resolution of the encoder, which can generally reach 0.001 ° or higher, while the control accuracy of stepper motors depends on the step angle, which is generally 1.8 ° or 0.9 °, and requires subdivision technology to improve accuracy, but still lower than servo motors.

Low frequency characteristics: Stepper motors are prone to low-frequency vibration during low-speed operation, which affects the smoothness and positioning accuracy of operation. Damping or subdivision techniques are needed to suppress vibration, while servo motors have no vibration phenomenon during low-speed operation, operate smoothly, and have the function of suppressing mechanical resonance.

Torque frequency characteristics: The output torque of a stepper motor decreases with the increase of speed, and sharply decreases at high speeds, so its maximum working speed is generally between 300-600r/min. The output torque of a servo motor is constant within the rated speed, and above the rated speed is constant power, so its maximum working speed is generally between 2000-3000r/min, and it has strong overload capacity.

Response speed: Stepper motors have significant inertia during start and stop, and speed changes require a certain amount of time. However, servo motors have a very fast response speed, taking only a few milliseconds from rest to rated speed, making them suitable for situations that require fast start and stop.

Control method: The control method of stepper motors is relatively simple, only requiring control of the number and direction of pulses, without feedback signals, but it is also prone to step loss or stalling. On the other hand, the control method of servo motors is more complex, requiring control of current magnitude and phase, feedback signals, but can also achieve precise position and speed control.

Application scenarios of motors

There are the following differences between servo motors and stepper motors in application scenarios:

Servo motor: Servo motors are suitable for applications that require high precision, high speed, high response, and high torque, such as CNC machine tools, robots, airplanes, missiles, etc.

Stepper motor: Stepper motors are suitable for applications that require low precision, low speed, low cost, and simple control, such as printers, scanners, engraving machines, packaging machines, etc.

In short, servo motors and stepper motors each have their own advantages and disadvantages, there is no absolute good or bad, only suitability and unsuitability. When choosing a motor, it is important to consider various factors such as control requirements, performance indicators, and cost budget to select the appropriate type of motor.

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