How to select the servo motor?
2020-07-31
In order to meet the requirements of mechanical equipment for high precision and rapid response, the servo motor should have a small moment of inertia and a large locked-rotor torque, and have the smallest possible time constant and starting voltage, as well as a long-term overload. Ability to meet the requirements of low-speed and large-torque, able to withstand frequent starting, braking and forward and reverse rotation. If you blindly choose a large-size motor, it will not only increase the cost, but also increase the size of the designed equipment and the structure is not compact. Therefore, when selecting a motor, you should fully consider the requirements of all aspects in order to give full play to the working performance of the servo motor; the selection principles and precautions of the servo motor are introduced below.
Steps to select servo motor model
1. Clarify the requirements of the motion condition of the load mechanism, that is, the speed of acceleration/deceleration, the motion speed, the weight of the mechanism, the motion mode of the mechanism, etc.
2. According to the operating conditions, select the appropriate load inertia calculation formula and calculate the load inertia of the mechanism.
3. According to the load inertia and the motor inertia, select an appropriate pseudo-selected motor specification.
4. Calculate the acceleration torque and deceleration torque by combining the initial selected motor inertia and load inertia.
5. Calculate the load torque based on the load weight, configuration method, friction coefficient, and operating efficiency.
6. The maximum output torque of the primary selected motor must be greater than the acceleration torque plus the load torque; if the conditions are not met, other models must be selected for calculation and verification until it meets the requirements.
7. Calculate the continuous instantaneous torque based on the load torque, acceleration torque, deceleration torque and holding torque.
8. The rated torque of the primary selected motor must be greater than the continuous instantaneous torque. If the conditions are not met, other models must be selected for calculation and verification until they meet the requirements.
9. Complete the selection.
Servo motor selection calculation method
1. Confirmation of speed and encoder resolution.
2. Conversion of load torque on the motor shaft and calculation of acceleration and deceleration torque.
3. Calculate the load inertia and match the inertia. Take Yaskawa servo motors as an example. The inertia of some products can be matched up to 50 times, but the smaller the actual, the better, so the accuracy and response speed are better.
4. For the calculation and selection of regenerative resistance, for servo, generally above 2kw, external configuration is required.
5. Cable selection, the encoder cable is twisted-pair shielded. For Japanese products such as Yaskawa Servo, the absolute encoder is 6 cores, and the incremental type is 4 cores.
The above selection method only considers the power of the motor. For linear motion, it is expressed by speed, acceleration and required external force. For rotary motion, it is expressed by angular velocity, angular acceleration and required torque. They can all be expressed as a function of time. The factor has nothing to do. obviously. The maximum power of the motor P motor should be greater than the peak power P peak required by the work load, but it is not enough. Power in the physical sense includes torque and speed, but they are limited in the actual transmission mechanism. of. Use peak value and T peak value to indicate the maximum or peak value. The maximum speed of the motor determines the upper limit of the deceleration ratio of the reducer, n upper limit = peak, maximum/peak. Similarly, the maximum torque of the motor determines the lower limit of the reduction ratio, n lower limit = T peak/T motor, maximum, if the lower limit of n is greater than The upper limit of n, the selected motor is inappropriate. Conversely, the range of feasible transmission ratios between the upper and lower limits can be determined through a broad analogy of each motor. It is not sufficient to only use peak power as the principle of selecting the motor, and the accurate calculation of the transmission ratio is very cumbersome.
How to choose a servo motor
1. First of all, you need to distinguish common motors, such as servo motors, spindle motors, asynchronous motors. You must clearly understand why servo motors are used. Servo motors are generally used in CNC systems. They are controllable and can achieve semi-closed loop control. And closed-loop control.
2. Our commonly used servo motor manufacturers include Siemens, Zhengde Intelligent Control, and some other manufacturers, but the selection process is similar. The following is an example of Siemens selection.
3. First of all, you need to calculate the load torque. The calculation of the load torque requires the calculation of the load force. The load force may be friction or cutting force. You must make a rough calculation based on your mechanical system. The unit of load torque is N.M. So we also need to know the rotating diameter (radius) of the workpiece.
4. Then calculate the moment of inertia of the workpiece according to the rotation speed of the workpiece and the load mass. Then it is necessary to convert the load torque and moment of inertia of the workpiece into the moment of inertia and load torque of the spindle.
Shenzhen Maintex Intelligent Control Co., Ltd.
Business Type:Manufacturer
Product Range:DC Motor , AC Motor , Stepper Motor
Products/Service:Stepper Motor , Brushless motor , Dc motor , treadmill used motor , Brushed Dc Motor , Fuji motor
Certificate:ISO14001 , ISO/TS16949 , ISO9001 , RoHS
Company Address:Zhengde Science Park, No. 8, Pingdi Street, Longgang District, Shenzhen, Guangdong, China
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