1. What is inertia?
Inertia: the amount of inertia of the movement of a substance (object).
Moment of inertia: A measure of the inertia of a rigid body when it rotates around an axis (the characteristic that a rotating object maintains its uniform circular motion or is at rest).
2. Low inertia and high inertia
The inertia of the servo motor is composed of the mass of the rotor itself and the external load. The greater the inertia, the less likely the object's motion state is to change. Both rotating and linear moving parts become the load inertia of the motor, and their sizes have different calculation methods.
3. Influence of inertia on servo motor operation
The load inertia on the motor shaft will have a great impact on the sensitivity of the motor and the accuracy of the entire servo system. Usually, when the load is smaller than the inertia of the motor rotor, the above impact is not significant. However, when the load inertia reaches or even exceeds 5 times the rotor inertia, the servo amplifier will not be able to operate within the normal adjustment range. Therefore, the use of this type of inertia should be avoided. Therefore, when designing the load, the volume and weight should be reduced as much as possible.
What do low inertia and high inertia of servo motors mean? What's the difference?
Moment of inertia = radius of rotation * mass
Low inertia means that the motor is relatively long and flat, and the main shaft inertia is small. When the motor makes repeated movements with high frequency, the inertia is small and the heat is small. Therefore, low inertia motors are suitable for high-frequency reciprocating motion. But the general torque is relatively small. High-inertia servo motors are relatively large and have large torque, and are suitable for situations where the torque is high but the reciprocating motion is not very fast. Because of the high-speed movement to stop, the driver needs to generate a large reverse drive voltage to stop the large inertia, which generates a lot of heat.
Inertia is a measure of the inertia of a rigid body rotating around an axis. Rotational inertia is a physical quantity that represents the rotational inertia of a rigid body. It is related to the mass of the rigid body and the distribution of the mass relative to the axis of rotation. (A rigid body refers to an object that will not change in an ideal state). When selecting, the motor inertia is also an important indicator of the servo motor. It refers to the inertia of the servo motor rotor itself, which is very important for the acceleration and deceleration of the motor. If the inertia cannot be matched well, the motor will move very unevenly.
Generally, motors with small inertia have good braking performance, quick start, acceleration and stop response, and good high-speed reciprocation. They are suitable for some light-load, high-speed positioning situations, such as some linear high-speed positioning mechanisms. Medium and large inertia motors are suitable for situations with large loads and high stability requirements, such as some circular motion mechanisms and some machine tool industries
If the load is relatively large or the acceleration characteristics are relatively large, and a motor with a small inertia is selected, it may cause too much damage to the motor shaft. The selection should be based on factors such as the size of the load and the size of the acceleration. The general selection manual has Related energy calculation formulas.
The optimal value for the response control of the servo motor driver to the servo motor is that the ratio of the load inertia to the motor rotor inertia is one, and the maximum value cannot exceed five times. Through the design of mechanical transmission device, the load can be made.
The ratio of inertia to motor rotor inertia is close to one or smaller. When the load inertia is really large and the mechanical design cannot make the ratio of the load inertia to the motor rotor inertia less than five times, a motor with a larger motor rotor inertia, a so-called large inertia motor, can be used. To achieve a certain response when using a motor with large inertia, the capacity of the driver should be larger.
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