How to choose the servo motor and stepper motor correctly?

time:2019-06-11 Browse:

  1,How to choose the servo motor and stepper motor correctly?

  Mainly depending on the specific application, it is simple to determine: the nature of the load (such as horizontal or vertical load), torque, inertia, speed, accuracy, acceleration and deceleration requirements, upper control requirements (such as port interface and communication In terms of requirements, the main control method is position, torque or speed. Whether the power supply is DC or AC, or battery powered, voltage range. This is used to determine the model of the motor and the associated drive or controller.
 

  2,Choose a stepper motor or a servo motor system?

  In fact, what kind of motor should be selected depends on the specific application, each has its own characteristics. Please see the table below.

  Stepper motor system Servo motor system
Torque range   Medium and small torque (generally below 20Nm)  Small, medium and large, full range
Speed range Low (generally below 2000RPM, high torque motor less than 1000RPM)   High (up to 5000RPM), DC servo motor can reach 20,000 to 20,000 rpm 
Control method   Mainly position control Diverse and intelligent control methods, position /
speed / torque mode
Smoothness Vibration at low speeds (but with subdivision drivers can be significantly improved) Good, run smooth
Precision Generally low, the subdivision drive is higher High (depending on the resolution of the feedback device)
Moment frequency characteristic When the speed is high, the torque drops quickly Good torque characteristics and hard features
Overload characteristic Out of step when overloaded Out of step when overloaded 
Feedback method Most of them are open loop control, and can also be connected to the encoder to prevent out of step Closed loop mode, encoder feedback 
Encoder type -  Photoelectric rotary encoder (incremental/absolute), resolver type
Responding speed  General Fast
Vibration resistant Good   General (rotary transformer type can withstand vibration)
Temperature High operating temperature General
Maintenance Basic maintenance free Better
Price Low High

  3, How to use a stepper motor driver?

  Depending on the current of the motor, a driver greater than or equal to this current is used. A subdivided drive can be used if low vibration or high precision is required. For high torque motors, use high voltage drives as much as possible to achieve good high speed performance.
 

  4,What is the difference between 2 phase and 5 phase stepper motors? How to choose?

  The 2-phase motor has a low cost, but the vibration at a low speed is large, and the torque at a high speed is rapidly lowered. The 5-phase motor has less vibration and high-speed performance, which is 30~50% higher than that of the 2-phase motor. It can replace the servo motor in some occasions.
 

  5, When is the DC servo system selected, what is the difference between it and AC servo?

  DC servo motors are divided into brushed and brushless motors.

  The brush motor has low cost, simple structure, large starting torque, wide speed regulation range, easy control and maintenance, but convenient maintenance (replacement of carbon brushes), electromagnetic interference, and environmental requirements. It can therefore be used in cost-sensitive general industrial and residential 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 method is flexible, and can be square wave commutation or sine wave commutation. The motor is maintenance-free, has high efficiency, low operating temperature, low electromagnetic radiation and long life, and can be used in various environments.

  AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. Currently, synchronous motors are generally used in motion control. It has a large power range and can achieve a large power. High inertia, the highest rotational speed is low, and it decreases rapidly as power increases. Therefore, it is suitable for applications with low speed and smooth operation.

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