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The difference between stepper motor and servo motor

The stepping motor

The stepping motor is an open-loop control element stepping motor that converts electrical pulse signals into angular displacement or linear displacement. In the case of non-overload, the motor speed and stop position only depend on the frequency of the pulse signal and the number of pulses, And not affected by the load change, when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, called "step angle", and its rotation is fixed The point of view runs step by step. The angular displacement can be controlled by controlling the number of pulses, so as to achieve the purpose of accurate positioning. At the same time, the speed and acceleration of the motor rotation can be controlled by controlling the pulse frequency to achieve the purpose of high speed.

 

The servo stepper motor

The servo stepper motor is also called the executive motor. In an automatic control system, it is used as an executive element to convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. The rotor inside the servo motor is a permanent magnet. The U/V/W three-phase electricity controlled by the driver forms an electromagnetic field. The rotor rotates under the action of this magnetic field. At the same time, the encoder of the motor feeds back the signal to the driver, and the driver compares the target with the feedback value. Compare the values ​​and adjust the angle of rotation of the rotor. The accuracy of the servo motor is determined by the accuracy of the encoder (number of lines). That is to say, the servo motor itself has the function of sending out pulses. Each time it rotates one angle, it will send out a corresponding number of pulses, so that the pulses of the servo drive and the servo motor encoder are formed In response, it is closed-loop control, and the stepper motor is open-loop control.

 

The difference between the stepper motor and servo motor is

1. Different control methods: one is open-loop control, the other is closed-loop control.

2. The low-frequency characteristics are different; the stepping motor is prone to low-frequency vibration at low speed. When it works at low speed, subdivision technology or damping technology is generally used to overcome low-frequency vibration. The servo motor runs very smoothly, even at low speed. The vibration will occur. The AC servo system has a resonance suppression function, which can cover the insufficient rigidity of the machine, and the system has a frequency analysis function (FFT) inside, which can detect the resonance point of the machine to facilitate the system adjustment.

3. The control accuracy is different. When the stepping motor has more beats and phases, its accuracy is higher. The servo motor is based on the built-in encoder. The more scale of the encoder, the higher the accuracy.

4. The torque frequency characteristics are different; the output torque of the stepping motor will decrease with the increase of the speed, and the AC servo motor has a constant torque output.
5. The overload capacity is different; stepper motors generally do not have overload capacity, while AC motors have stronger overload capacity.

6. The speed response performance is different; it takes hundreds of milliseconds for a stepper motor to accelerate from a standstill to working speed, while the AC servo system has better acceleration performance, generally only a few milliseconds, and can be used in control situations that require fast start and stop.

7. The operating performance is different; 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 steps or block the phenomenon. When the speed is too high, it is easy to overshoot. The AC servo drive system is closed-loop Control, the driver can directly sample the feedback signal of the motor encoder, and the position loop and the speed loop are formed inside. Generally, the stepping motor will not lose steps or overshoot, and the control performance is more reliable. More info pls click here: Servo Motor Manufacturer & Supplier

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