How to control the speed and torque of the electronic universal test machine

Electronic universal testing machineSpeed ​​control and torque control of electronic universal test machines are controlled by analog quantity. The position control of the electronic universal test machine is controlled by pulse generation. What specific control method should be chosen according to the customer's requirements and what kind of motion functions should be met.
If you have no requirements for the speed and position of the motor's electronic universal tester, just output a constant electron universal tester torque, of course, use the electronic universal tester torque mode.
If there are certain accuracy requirements for the position of the electronic universal tester and the speed of the electronic universal tester, but are not very concerned about the torque of the real-time electronic universal tester, it is not convenient to use the electronic universal tester torque mode, and it is better to use the electronic universal tester speed or the position mode of the electronic universal tester. If the upper controller has a better closed-loop control function, the speed control effect of using the electronic universal test machine will be better. If the requirements themselves are not very high, or there are basically no real-time requirements, the position control method of the electronic universal test machine does not have very high requirements for the upper controller.
Judging from the speed of the servo driver's response, the torque mode calculation amount of the electronic universal test machine is small, and the driver responds to the control signal quickly; the position mode calculation amount of the electronic universal test machine is slow to respond to the control signal.
When there are relatively high requirements for dynamic performance in motion, the motor needs to be adjusted in real time. Then if the controller itself has a slow speed in computing the electronic universal test machine (such as PLC, or low-end motion controller), the electronic universal test machine position control is used. If the controller calculates the electronic universal test machine at a faster speed, you can use the electronic universal test machine speed method to move the electronic universal test machine position ring from the driver to the controller to reduce the workload of the driver and improve efficiency (such as most mid-to-high-end motion controllers); if there is a better upper controller, you can also use the electronic universal test machine torque method to move the electronic universal test machine speed ring away from the driver. This is generally only a high-end dedicated controller to do this, and there is no need to use a servo motor at this time.
Generally speaking, whether the drive control is good or not, each manufacturer says it does it himself, but now there is a more intuitive comparison method called response bandwidth. When the torque control of the electronic universal tester or the speed control of the electronic universal tester is used to give it a square wave signal through the pulse generator, causing the motor to continuously rotate and reverse, and continuously increase the frequency. The oscilloscope shows a sweep signal. When the vertex of the envelope reaches 70.7% of the value, it means that the step has been lost. The frequency at this time can show whose product is great. The general current loop can reach more than 1000Hz, while the speed loop of the electronic universal tester can only reach a few dozen hertz.
To put it in a more professional way:
1. Torque control of electronic universal tester: The torque control method of electronic universal tester is to set the torque of the motor shaft to the outside output by the input of external analog quantity or the assignment of direct address. Specifically, for example, if 10V corresponds to 5Nm, the motor shaft output is 2.5Nm when the external analog quantity is set to 5V: 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 size can be changed by instantly changing the setting of the analog quantity, or it can be changed by communication method to change the value of the corresponding address.
The application is mainly in winding and unwinding devices that have strict requirements on the force of the material, such as wire radiating devices or fiber optic equipment. The torque setting of the electronic universal test machine must be changed at any time according to the change of the winding radius to ensure that the force of the material will not change with the change of the winding radius.
2. Position control of electronic universal test machine: The position control mode of electronic universal test machine generally determines the speed of rotation of electronic universal test machine through the frequency of external input pulses, and determines the rotation angle through the number of pulses. Some servos can directly assign the speed and displacement of electronic universal test machine through communication. Since the position mode of the electronic universal tester can strictly control the speed of the electronic universal tester and the position of the electronic universal tester, it is generally used in positioning devices. Application areas such as CNC machine tools, printing machinery, etc.
3. Electronic universal test machine speed mode: The speed of the rotating electronic universal test machine can be controlled through the input of analog quantity or the frequency of pulses. The electronic universal test machine speed mode can also be positioned when the outer ring PID control with the upper control device is controlled, but the position signal of the motor or the position signal of the direct load of the electronic universal test machine must be given to the upper position for operation. The position mode of the electronic universal tester also supports direct load outer ring to detect the position signal of the electronic universal tester. At this time, the encoder at the shaft end of the motor only detects the motor speed, and the position signal of the electronic universal tester is provided by the detection device at the direct end of the load. This advantage is that it can reduce errors during the intermediate transmission process and increase the positioning accuracy of the entire system.
4. Let’s talk about 3 rings. The servo is generally controlled by three rings. The so-called three rings are three closed-loop negative feedback PID adjustment systems. The PID ring inside is the current ring, which is completely carried out inside the servo driver. The output current of the driver to each phase of the motor is detected through the Hall device, and the negative feedback current is set for PID adjustment, so that the output current is as close as possible to the set current. The current ring controls the torque of the motor electronic universal test machine, so the driver's calculation is small and the dynamic response is fast in the torque mode of the electronic universal test machine.
The second ring is the speed ring of the electronic universal test machine. The negative feedback PID adjustment is performed through the detected signal of the motor encoder. The PID output in its ring is directly the setting of the current ring. Therefore, the speed ring of the electronic universal test machine includes the speed ring and the current ring. In other words, any mode must use the current ring. The current ring is the basis of control. While the speed and position of the electronic universal test machine are controlled, the system is actually controlling the current (torque of the electronic universal test machine) to achieve the corresponding control of the speed of the electronic universal test machine and the position of the electronic universal test machine.
The third ring is the position ring of the electronic universal test machine. It is the outer 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. It must be determined according to the actual situation. Since the internal output of the position control ring of the electronic universal test machine is the setting of the speed ring of the electronic universal test machine, the system performs all 3 rings in the position control mode of the electronic universal test machine. At this time, the system's calculation volume and dynamic response of the electronic universal test machine are also slow.