Dry goods - those things we should know
The difference between servo motor and stepper motor:
1, low frequency characteristics are different
Stepper motors are prone to low frequency vibration at low speeds. The vibration frequency is related to the load condition and the performance of the driver. It is generally considered that the vibration frequency is half of the take-off frequency of the motor no-load. This low frequency vibration phenomenon, which is determined by the working principle of the stepper motor, is very detrimental to the normal operation of the machine. When the stepper motor works at low speed, damping technology should generally be used to overcome the low frequency vibration phenomenon, such as adding a damper to the motor or using subdivision technology on the drive. The AC servo motor runs very smoothly, and vibration does not occur even at low speeds. The AC servo system has a resonance suppression function, which can cover the rigidity of the machine, and has a frequency analysis function (FFT) inside the system, which can detect the resonance point of the machine and facilitate system adjustment.
2, the characteristics of the moment frequency are different
The output torque of the stepping motor decreases as the speed increases, and it drops sharply at higher speeds, so the maximum operating speed is generally 300-600 RPM. The AC servo motor is a constant torque output, that is, it can output the rated torque within its rated speed (generally 2000RPM or 3000RPM), and it is a constant power output above the rated speed.
3, different overload capabilities
Stepper motors generally do not have overload capability. The AC servo motor has a strong overload capability. Because there is no such overload capability in stepper motors, in order to overcome this moment of inertia during the selection, it is often necessary to select a motor with a large torque. However, the machine does not need such a large torque during normal operation, and a torque occurs. The phenomenon of waste.
4, different operating performance
The control of the stepping motor is open-loop control. If the starting frequency is too high or the load is too large, it may be lost or blocked. If the speed is too high during the stop, the overshoot may occur. Therefore, in order to ensure the control accuracy, it should be handled well. The problem of rising and falling speed. The AC servo drive system is closed-loop control. The drive can directly sample the feedback signal of the motor encoder. The internal position loop and speed loop are formed. Generally, the stepless motor is lost or overshooted, and the control performance is more reliable.
5, the speed response performance is different
It takes 200 to 400 milliseconds for the stepper motor to accelerate from standstill to the operating speed (typically several hundred revolutions per minute). The AC servo system has better acceleration performance. In summary, the AC servo system is superior to the stepper motor in many performance aspects. However, in some occasions where the requirements are not high, stepper motors are often used to perform the motor. Therefore, in the design process of the control system, it is necessary to comprehensively consider the control requirements, cost and other factors, and select the appropriate control motor.
