When buying a stepper motor, it is necessary to make a clear comparison between it and ac servo motor. There are probably the following differences and some parts:
Stepper motor is a discrete motion device, which has essential relationship with modern digital control technology.In the present domestic digital control system, the stepper motor is widely used.With the appearance of full digital AC servo system, AC servo motor is more and more applied in digital control system.In order to adapt to the development trend of digital control, most of the motion control systems adopt stepper motor or full digital AC servo motor as the executive motor.Although they are similar in control mode (pulse train and directional signal), they are quite different in performance and application.The performance of the two is compared.
1. Different operation performance
The stepper motor is controlled by open-loop control. If the starting frequency is too high or the load is too large, it is easy to lose step or stall; if the speed is too high, it is easy to overshoot when stopping. Therefore, in order to ensure the control accuracy, the problem of speed rise and speed fall should be handled well.Ac servo drive system is closed-loop control. The driver can directly sample the feedback signals of the motor encoder. The inner part consists of position ring and speed ring.
2. Different speed response performance
It takes 200 ~ 400 milliseconds for a stepper motor to accelerate from rest to working speed (generally hundreds of revolutions per minute).The acceleration performance of AC servo system is good. Taking Panasonic MSMA 400W AC servo motor as an example, it only takes a few milliseconds to accelerate from rest to its rated speed of 3000RPM, which can be used in control occasions requiring quick start and stop.
To sum up, AC servo system is superior to stepper motor in many performance aspects.However, stepper motor is often used to perform the motor in some less demanding occasions.Therefore, in the design process of the control system to consider the control requirements, cost and other factors, choose the appropriate control motor.