Three control modes of servo motor in Kunshan mould factory

1. Torque control: the torque control method is to set the external output torque of the motor shaft through the input of the external analog quantity or the assignment of the direct address. For example, if 10V corresponds to 5nm, when the external analog quantity is set to 5V, the output of the motor shaft is 2.5nm: if the motor shaft load is less than 2.5nm, the motor will rotate forward, when the external load is equal to 2.5nm, the motor will not rotate, and when it is greater than 2.5nm When the motor reverses (usually under gravity load). The torque can be changed by changing the setting of analog quantity in real time, or the corresponding address value can be changed by means of communication.

It is mainly used in the winding and unwinding devices which have strict requirements on the stress of materials, such as wire laying device or optical fiber pulling device. The torque setting shall be changed at any time according to the change of winding radius to ensure that the stress of materials will not change with the change of winding radius.

2. Position control: the position control mode generally determines the rotation speed by the frequency of external input pulse, and determines the rotation angle by the number of pulses. Some servos can directly assign the speed and displacement through communication. Because the position mode can control the speed and position strictly, it is generally used in the positioning device. Applications such as CNC machine tools, printing machinery and so on.

3. Speed mode: the speed can be controlled by the input of analog quantity or the frequency of pulse. The speed mode can also be positioned when the external loop PID control of the upper control device is available. However, the position signal of the motor or the position signal of the direct load must be sent to the upper feedback for calculation. The position mode also supports the direct load outer ring to detect the position signal. At this time, the encoder at the motor shaft end only detects the motor speed, and the position signal is provided by the direct final load end detection device. This advantage lies in that it can reduce the error in the intermediate transmission process and increase the positioning accuracy of the whole system.

4. Talk about 3-loop, servo is generally controlled by 3-loop, so-called 3-loop is 3 closed-loop negative feedback PID regulation system. The inner PID loop is the current loop, which is completely carried out inside the servo driver. The output current of each phase of the driver to the motor is detected by the hall device, and the setting of negative feedback to the current is adjusted by PID, so as to achieve the output current as close as possible to the setting current, and the current loop is to control the motor torque, so the operation of the driver is the smallest and the dynamic response is the smallest in the torque mode Should be the fastest.

The second loop is the speed loop, which adjusts the negative feedback PID by detecting the signal of the motor encoder. Its PID output in the loop is directly the setting of the current loop, so the speed loop control includes the speed loop and the current loop. In other words, the current loop must be used in any mode, and the current loop is the root of the control. At the same time of the speed and position control, the system also carries out the current actually (torque) to achieve the corresponding control of speed and position.

The third ring is the position ring, which is the outermost ring. It can be built between the driver and the motor encoder or between the external controller and the motor encoder or the final load according to the actual situation. Since the internal output of the position control loop is the setting of the speed loop, all three loops of the system are calculated in the position control mode. At this time, the system has a large amount of calculation, and the dynamic response speed is the slowest.