Servo motor and stepper motor

Update date:2018-04-24 Source:MAXGE

Servo motor and stepper motor

The general structure of an electric servo system is three closed-loop controls, namely a current loop, a speed loop, and a position loop. Under normal circumstances, for AC servo drives, various functions such as position control, speed control, and torque control can be achieved by manually setting the internal function parameters. So what do you need to know about servo motors?


1. How to choose servo motor and stepper motor correctly?

A: The main application depends on the specific situation, simply to determine: the nature of the load (such as horizontal or vertical load, etc.), torque, inertia, speed, accuracy, acceleration and deceleration and other requirements, the superior control requirements (such as the port interface And communication requirements), the main control method is position, torque or speed mode. The power supply is DC or AC power, or battery powered, with a voltage range. Use this to determine the type of motor and actuator or controller.

2. Choose stepper motor or servo motor system?

A: Actually, what type of motor should be selected depends on the specific application and each has its own characteristics.

3, how to use stepper motor driver?

Answer: According to the current of the motor, use a driver that is greater than or equal to this current. If you need low vibration or high precision, subdivided drivers can be used. For large torque motors, use high-voltage drivers as much as possible to achieve good high-speed performance.

What is the difference between 4-, 2-phase, and 5-phase stepper motors?

A: The cost of the 2-phase motor is low, but the vibration at low speed is large, and the torque at high speed drops quickly. The 5-phase motor has less vibration and high-speed performance, which is 30-50% higher than the speed of 2-phase motors. It can replace servo motors in some applications.

5, when to use the DC servo system, it is different from AC servo?

Answer: DC servo motors are divided into brushed and brushless motors.

The brush motor has low cost, simple structure, large starting torque, wide speed range, easy control and maintenance, but easy maintenance (for carbon brush), electromagnetic interference, and environmental requirements. It can therefore be used in cost-sensitive general industrial and civil applications.

The brushless motor is small in size, light in weight, large in output, fast in response, high in speed, small in inertia, smooth in rotation, and stable in torque. The control is complex and it is easy to realize intelligence. The electronic commutation mode is flexible, and it can be changed by square wave or sine wave. The motor is maintenance-free, high efficiency, low operating temperature, low electromagnetic radiation, long life, and can be used in various environments.

AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. At present, synchronous motors are generally used in motion control. Its power range is large, and it can achieve large power. With high inertia, the maximum rotational speed is low, and it rapidly decreases with increasing power. Therefore, it is suitable for low speed and smooth operation.


6, when using the motor to pay attention to the problem?

A: The following checks should be made before the power is turned on:

1) The power supply voltage is appropriate (overvoltage is likely to cause damage to the drive module); the +/- polarity of the DC input must not be connected incorrectly, the motor model or current setpoint on the drive controller is appropriate (do not start Too large); 2) The control signal lines are connected securely, the shielding of the industrial site is best to consider (such as the use of twisted pair); 3) do not start when the need to connect all the lines connected to only the most basic system After you run well, connect gradually.

4) Be sure to find out the grounding method, or use floating air.

5) During the first half hour of operation, the status of the motor should be closely observed, such as whether the movement is normal, sound and temperature rise, and the problem is immediately shut down for adjustment.


Stepper motor sometimes loses its ability to start up. What is the problem?

When the motor enters the start-up mode, it may not move at all, or move back and forth in the field. Sometimes it will run out of synchronization. Generally, the following aspects should be considered:

1) Whether the motor torque is large enough or not can drive the load, so we generally recommend that the user select a motor with a torque that is 50% to 100% larger than the actual demand, because the stepper motor cannot operate under overload, even if it is instantaneous. It will cause a loss of balance, stop in serious cases or move in an irregular manner.

2) Whether the input walking pulse current from the upper controller is large enough (generally >10mA), so that the optocoupler can be turned on steadily, and whether the input frequency is too high, resulting in no reception if the output circuit of the upper controller For CMOS circuits, CMOS input drivers are also used.

3) Whether the starting frequency is too high, whether the acceleration process is set in the start-up procedure, it is better to accelerate from the start frequency specified by the motor to the set frequency. Even if the acceleration time is short, it may be unstable or even inactive. .

4) When the motor is not fixed, this condition sometimes occurs and it is normal. Because, in fact, a strong resonance of the motor is caused at this time, leading to an out-of-step condition. The motor must be fixed.

5) For a 5-phase motor, the phase connection is wrong and the motor cannot work.

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