Pressure feedback servo valve is a kind of high-precision control element widely used in hydraulic control system, which can adjust the flow or pressure in real time according to the change of system pressure, so as to realize accurate control of actuator. Its regulation performance directly affects the stability, response speed and control accuracy of the whole hydraulic system. Therefore, it is very important to adjust the pressure feedback servo valve correctly to ensure the normal operation of the system.
First, the basic structure and working principle of pressure feedback servo valve
Pressure feedback servo valve is usually composed of servo motor, pilot control valve, main spool, feedback spring and pressure sensor. It detects the system pressure through the pressure sensor and feeds back the signal to the controller. The controller adjusts the action of the servo motor according to the deviation between the set value and the actual value, thus changing the opening of the valve port and realizing the closed-loop control of the system pressure.
Second, the preparation work before adjustment
Before adjusting the pressure feedback servo valve, ensure that the system is in normal working condition:
1. Check the cleanliness of the system oil: avoid impurities blocking the valve core or damaging the seal;
2. Confirm that the system oil temperature is stable: too high or too low oil temperature will affect the viscosity, thus affecting the response of the valve;
3. Check the electrical connection and feedback signal: ensure the normal signal transmission of the sensor and controller;
4. Read the technical manual: be familiar with the structure and parameters of the valve and the function of the adjusting knob or button.
Three, the pressure feedback servo valve adjustment steps
1. Initial setting
Set the system pressure to the lowest value, close the load circuit, start the hydraulic pump step by step, and observe whether the system pressure rises steadily.
2. Proportional gain adjustment (P adjustment)
The proportional gain determines the response strength of the controller to the error. Gradually increase the gain during adjustment until the system responds quickly and has no obvious overshoot. If the gain is too high, the system will oscillate; If it is too low, the response is slow.
3. Integral adjustment (I adjustment)
Integration is used to eliminate static errors. On the basis of proportional adjustment, the integral time constant is slowly increased to make the system pressure tend to be stable and eliminate the residual.
4. Differential adjustment (D adjustment)
Differential link can improve the dynamic response characteristics of the system and suppress overshoot. Proper adjustment of differential parameters is helpful to improve the stability of the system.
5. Pressure feedback signal calibration
Use a standard pressure gauge to check the system pressure to ensure that the feedback signal is consistent with the actual pressure. If there is any deviation, the parameters of feedback circuit or controller need to be adjusted.
6. Load test and dynamic response observation
After the initial adjustment, the actual load is connected, and the dynamic test is carried out to observe the pressure fluctuation and response time, and the PID parameters are fine-tuned again if necessary.
Four, adjust the matters needing attention
-Frequent and large-scale adjustment of parameters should be avoided in the process of adjustment, so as not to cause system shock;
-Re-adjustment may be required under different working conditions (such as temperature and load changes);
-Regular maintenance and calibration is the key to ensure the long-term stable operation of the servo valve;
-If the system has abnormal noise, large pressure fluctuation or slow response, etc., the cause of the failure should be investigated in time, and professionals should be invited to assist if necessary.
V. Conclusion
As the core control element in the hydraulic system, the pressure feedback servo valve needs to comprehensively consider the system characteristics and working environment in its adjustment process. By reasonably adjusting PID parameters, calibrating feedback signals and dynamic testing, the control accuracy and stability of the system can be effectively improved. Mastering the correct adjustment method not only helps to prolong the service life of the equipment, but also ensures the safety and efficiency of the production process.