Analysis of the difference between stepper motor and servo motor

Stepper motor is the electrical pulse signal into angular displacement or line displacement of the open-loop control element stepper motor parts, in the case of non-overload, the motor speed, stop position only depends on the frequency and number of pulse signals, and is not affected by load changes, when the stepper driver receives a pulse signal, It drives the stepper motor to rotate a fixed Angle in the direction set, called the "step Angle", and its rotation is run step by step at a fixed Angle. The angular displacement can be controlled by controlling the number of pulses, so as to achieve the purpose of accurate positioning, and the speed and acceleration of the motor can be controlled by controlling the pulse frequency, so as to achieve the purpose of high speed.

The servo motor, also known as the executive motor, is used as an executive element in the automatic control system to convert the received electrical signal into the angular displacement or angular speed output on the motor shaft. The rotor inside the servo motor is a permanent magnet, and the U/V/W three-phase electricity controlled by the driver forms an electromagnetic field, and the rotor rotates under the action of this magnetic field, while the encoder of the motor comes with a feedback signal to the driver, and the driver adjusts the rotation Angle of the rotor according to the feedback value and the target value. The precision of the servo motor is determined by the accuracy of the encoder (line number), that is to say, the servo motor itself has the function of issuing pulses, and it will issue the corresponding number of pulses at each rotation Angle, so that the servo driver and the pulse of the servo motor encoder echo, so it is closed-loop control, and the stepper motor is open-loop control.

The difference between stepper motor and servo motor is: 1, the control accuracy is different. The more the number of phases and beats of the stepper motor, the higher its accuracy, the servo motor takes a block in its own encoder, the more the encoder scale, the higher the accuracy. 2. Different control methods; One is open loop control and the other is closed loop control. 3, low frequency characteristics are different; Stepper motor at low speed is prone to low-frequency vibration phenomenon, when it works at low speed generally use damping technology or subdivision technology to overcome low-frequency vibration phenomenon, servo motor operation is very smooth, even at low speed will not appear vibration phenomenon. The AC servo system has a resonance suppression function to cover the lack of rigidity of the machine, and the system has a frequency resolution function (FFT), which can detect the resonance point of the machine for system adjustment. 4, the moment frequency characteristics are different; The output torque of the stepper motor will decrease with the increase of the speed, the AC servo motor is a constant torque output, 5, the overload capacity is different; Stepper motors generally do not have overload capacity, while AC motors have strong overload capacity. 6. Different operating performance; The control of the stepper motor is open-loop control, the starting frequency is too high or the load is too large, and the speed is too high when the stop speed is too high, the overrush phenomenon is easy to occur. The AC servo drive system is closed-loop control, the driver can directly sample the feedback signal of the motor encoder, and the internal position ring and speed ring are formed. Generally, the stepper motor will not lose step or overrush. More reliable control performance. 7, speed response performance is different; The stepper motor needs hundreds of milliseconds to accelerate from static to working speed, and the AC servo system has better acceleration performance, generally only a few milliseconds, and can be used for control occasions requiring rapid start and stop.