Servo motors generally have three control modes: speed control mode, torque control mode, and position control mode.
Both speed control and torque control are controlled by analog quantities. Position control is controlled by pulse. The specific control method should be selected according to the customer's requirements and what kind of sports function is satisfied.
If you do not have any requirements on the speed and position of the motor, just output a constant torque, of course, using the torque mode.
If there is a certain accuracy requirement for position and speed, and the real-time torque is not very concerned, it is not convenient to use the torque mode, and the speed or position mode is better. If the host controller has a better closed-loop control function, the speed control effect will be better. If the requirements are not very high, or there is basically no real-time requirement, there is no high requirement for the upper controller by the position control method.
In terms of the response speed of the servo drive, the torque mode calculation amount is the smallest, the driver has the fastest response to the control signal; the position mode calculation amount is the largest, and the driver has the slowest response to the control signal.
When there is a high requirement for dynamic performance in motion, the motor needs to be adjusted in real time. Then if the controller itself is slow (such as PLC, or low-end motion controller), it is controlled by position. If the controller is running faster, you can use the speed mode to move the position loop from the drive to the controller, reducing the workload of the drive and improving efficiency (such as most mid-to-high-end motion controllers); if there is better upper control It can also be controlled by torque, and the speed loop is also removed from the drive. This is generally only a high-end dedicated controller to do this, and at this time, there is no need to use a servo motor.
Another way of saying this is:
1. Torque control:
The torque control mode is to set the external output torque of the motor shaft by external analog input or direct address assignment, which is expressed as, for example, 10V corresponding to 5Nm, when the external analog is set to 5V, the motor shaft The output is 2.5Nm: if the motor shaft load is lower than 2.5Nm, the motor rotates forward, the motor does not rotate when the external load is equal to 2.5Nm, and the motor reverses when it is greater than 2.5Nm (usually generated under gravity load). The set torque can be changed by changing the analog setting in real time, or by changing the value of the corresponding address by communication. The application is mainly used in the winding and unwinding devices which have strict requirements on the material stress, such as the wire drawing device or the fiber drawing device. The torque setting is changed according to the change of the winding radius to ensure the stress of the material is not It will change as the winding radius changes.
2. Position control:
The position control mode generally determines the rotation speed by the frequency of the externally input pulse, and determines the angle of rotation by the number of pulses. Some servos can directly assign speed and displacement by communication. Since the position mode has strict control over speed and position, it is generally applied to positioning devices. Applications such as CNC machine tools, printing machinery, etc.
3. Speed ​​mode:
The rotation speed can be controlled by the analog input or the frequency of the pulse. The speed mode can also be positioned when the outer ring PID of the upper control device is controlled, but the position signal of the motor or the position signal of the direct load must be given to the upper position. Feedback is used for calculations. The position mode also supports the direct load outer loop detection position signal. At this time, the encoder at the motor shaft end only detects the motor speed, and the position signal is directly finalized.
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