Three servo mode selection methods for motor servo control
Motor servo control three modes of selection, the general servo has three control methods: speed control mode, torque control mode, position control mode. What I want to know is based on what is the choice of these three control methods? Both speed control and torque control are controlled by analog quantities. Position control is controlled by pulse.
How to choose the control method?
The specific control method should be selected according to the requirements of the customer 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 it is not very concerned about real-time torque, it is better to use speed or position mode. 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. If the controller itself is slow (such as PLC, or low-end motion controller), it is controlled by position. If the controller is running at a faster speed, the position loop can be moved from the drive to the controller in a speed mode to reduce the workload of the drive and improve efficiency; if there is a better upper controller, it can also be controlled by torque. The speed loop is also removed from the drive, which is usually only a high-end dedicated controller.
Generally speaking, the control of the drive is good or bad, and there is a relatively straightforward comparison method called response bandwidth. When torque control or speed control, a square wave signal is given to it by the pulse generator, so that the motor continuously rotates and reverses continuously, and the frequency is constantly increased. The oscilloscope displays a sweep signal when the envelope is When the apex reaches 70.7% of the highest value, it means that it has lost the step. At this time, the frequency can explain the quality of the control. Generally, the current loop can achieve 1000HZ or more, and the speed loop can only achieve tens of Hertz.
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.
