Release Date：2023-02-14 10:59:11 Popularity：
Servo motors are widely used in the field of automation equipment, and are usually used to drive more precise speed or position control components in projects. Designers of automation equipment often need to face a variety of motor selection problems with different needs, and the motors provided by the suppliers are also varied and have many parameters, which often make beginners confused.
1. Application scenarios
Control motors in the field of automation can be divided into servo motors, stepper motors, frequency conversion motors, etc. For components that require more precise speed or position control, servo motor drives will be selected. The control method of frequency converter + variable frequency motor is a control method that changes the motor speed by changing the power frequency of the input motor. Generally only used for motor speed control.
Compared with stepper motors, servo motors use closed-loop control, while stepper motors use open-loop control; servo motors use rotary encoders to measure accuracy, and stepper motors use step angles. The accuracy of the former at the ordinary product level can reach hundreds of times that of the latter; the control method is similar (pulse or direction signal).
2. Power supply
Servo motors can be divided into AC servo motors and DC servo motors from the power supply.
The two are better choices. For general automation equipment, Party A will provide a standard 380V industrial power supply or 220V power supply. At this time, it is sufficient to select the servo motor corresponding to the power supply, eliminating the need for conversion of the power supply type. However, some equipment, such as the shuttle board in the three-dimensional warehouse, the AGV trolley, etc., due to their own mobile nature, most of them use their own DC power supply, so DC servo motors are generally used.
According to the design of the action mechanism, consider whether there will be a reverse tendency of the motor in the power-off state or in the static state. If there is a tendency to reverse, it is necessary to choose a servo motor with a brake.
4. Selection calculation
Before the selection calculation, the position and speed requirements of the end of the mechanism must be determined first, and then the transmission mechanism must be determined. At this point, the servo system and the corresponding reducer can be selected. During the selection process, the following parameters are mainly considered:
Power and speed: According to the structure form and the speed and acceleration requirements of the final load, calculate the required power and speed of the motor. It is worth noting that it is usually necessary to select the reduction ratio of the reducer in combination with the speed of the selected motor.
In the actual selection process, for example, if the load moves horizontally, the formula P=T*N/9549 often cannot be clearly calculated (the torque cannot be accurately calculated) due to the uncertainty of the friction coefficient and wind load coefficient of each transmission mechanism. In practice, it is also found that the acceleration and deceleration phases often require the greatest power when using servo motors. Therefore, through T=F*R=m*a*R, the power of the required motor and the reduction ratio of the reducer can be quantitatively calculated (m: load mass; a: load acceleration; R: load rotation radius).
The following points need to be paid attention to: the power surplus coefficient of the motor; the transmission efficiency of the mechanism; whether the input and output torque of the reducer meet the standard and have a certain safety factor; whether there will be a possibility of increasing the speed in the later stage.
Inertia matching: To achieve high-precision control of the load, it is necessary to consider whether the inertia of the motor and the system match.
Accuracy requirements: Calculate whether the control accuracy of the motor can meet the requirements of the load after the change of the reducer and the transmission mechanism. The reducer or some transmission mechanisms have a certain backlash, which needs to be considered.
Control matching: This aspect is mainly to communicate and confirm with the electrical designer, such as whether the communication mode of the servo controller matches with the PLC, the type of encoder and whether data needs to be exported, etc.
At present, there are many brands of servo motors on the market, and their performances vary widely. Generally speaking, if you are not short of money, choose European and American ones, and if you are a little short of money, choose Japanese ones, and then Taiwan and mainland China. According to past experience, there is no problem with the basic performance of the domestic servo motor body, but there is a certain gap in the control algorithm, integration and stability of the main servo controller.