The difference between servo motor and stepper motor of principle and performance
Both the stepper motor and the servo motor belong to the control motor. We know that the main function is to convert and transmit signals. What is the difference between the stepper motor and the servo motor that also belong to the control motor?
A stepper motor is a motor that converts a pulse signal into a line displacement or an angular displacement using the principle of an electromagnet. Each time an electric pulse is applied, the motor rotates at an angle to drive the machine to move a short distance.
The role of the servo motor is to drive the control object. The torque and speed of the controlled object are controlled by the signal voltage. When the magnitude and polarity of the signal voltage change, the rotation speed and direction of the motor are also followed.
First, the difference between servo motor and stepper motor principle
1. Working principle of stepper motor
A stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction.
Degree (called "step angle"), its rotation is run step by step at a fixed angle. The angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning;
The speed and acceleration of the motor rotation can be controlled by controlling the pulse frequency to achieve the purpose of speed regulation.
2. The working principle of the servo motor
The rotor inside the servo motor is a permanent magnet, and the U/V/W three-phase electric motor controlled by the driver forms an electromagnetic field, and the rotor rotates under the action of the magnetic field, and the encoder feedback signal of the motor is supplied to the drive.
The driver compares the feedback value with the target value to adjust the angle at which the rotor rotates. The accuracy of the servo motor is determined by the accuracy (number of lines) of the encoder.
Second, the difference between servo motor and stepper motor performance
The more the number of phases and the number of beats of the stepping motor, the higher its accuracy. The servo motor takes the block in its own encoder. The more the scale of the encoder, the higher the accuracy.
2. Low frequency characteristics
Stepper motor is prone to low frequency vibration at low speed. When it works at low speed, it usually adopts damping technology or subdivision technology to overcome the low frequency vibration phenomenon. The servo motor runs very smoothly, that is,so that vibration does not occur at low speeds;
3. Moment frequency characteristics
The output torque of the stepping motor decreases with the increase of the rotational speed, and will drop sharply at high speed. The servo motor is a constant torque output at the rated speed and a constant power output at the rated speed;
4. Overload capability
The stepping motor does not have overload capability, and the servo motor has strong overload capability;
5. Operating performance
The control of the stepping motor is open-loop control, the starting frequency is too high or the load is too large, and it is easy to lose step or block. When the speed is too high, the overshoot phenomenon is easy to occur, and the AC servo drive system is closed loop control ystem, the driver can directly sample the motor encoder feedback signal, internally form the position loop and speed loop, generally there will be no stepping motor over-step or overshoot phenomenon, the control performance is morereliable;
6. Speed response performance
It takes hundreds of milliseconds for the stepper motor to accelerate from standstill to the working speed. The AC servo system has better acceleration performance, generally only a few milliseconds, and can be used in control situations requiring fast start and stop.