First, the basic principle of proportional servo valve
Proportional servo valve is a kind of control valve between ordinary hydraulic valve and servo valve. It controls the displacement of the valve core through the input electrical signal (usually current or voltage), thus adjusting the flow and pressure of hydraulic oil and realizing the continuous control of the position, speed or force of the actuator (such as hydraulic cylinder or motor). The “opening” of the valve core, that is, the opening degree of the valve port, determines the throughput of hydraulic oil and is the core parameter of control accuracy.
Second, the main factors affecting the accuracy of opening adjustment
1. Stability of electric signal input: Proportional servo valves usually use proportional electromagnets to drive the spool to move, and the fluctuation of input signals will lead to the change of opening.
2. Machining accuracy of valve core and valve body: High-precision mechanical cooperation can reduce hysteresis and dead zone and improve adjustment accuracy.
3. Cleanliness and viscosity of oil: pollutants may cause the valve core to stick and affect the response; The change of oil viscosity will also affect the flow control.
4. System pressure fluctuation: System pressure fluctuation caused by load change will indirectly affect the actual opening effect of the valve.
Third, the method of accurately adjusting the opening of proportional servo valve
1. Closed-loop feedback control
Closed-loop control is one of the most effective methods to improve the accuracy of opening adjustment. By installing displacement sensor or pressure sensor on the valve core or actuator, the actual output is fed back to the controller (such as PLC or special controller), and the controller adjusts the input signal according to the deviation between the set value and the feedback value, and corrects the position of the valve core in real time, thus ensuring the stability of the opening.
2. PID parameter optimization
In the closed-loop control system, it is very important to set PID (proportional, integral and differential) parameters reasonably to improve the control accuracy. Through the step response test of the system, the PID parameters are adjusted to achieve the best response time, minimum overshoot and steady-state error, so as to realize the accurate adjustment of the valve opening.
3. Regular calibration and maintenance
In order to ensure the accuracy of long-term operation, it is necessary to calibrate the proportional servo valve regularly. Use standard signal source to input different current/voltage signals, measure the actual displacement value of the valve core, draw the input-output curve, judge whether there is nonlinearity or hysteresis, and adjust or replace worn parts.
4. Use high-performance control amplifier
Choosing a control amplifier with high resolution and stable output can significantly improve the control accuracy of the signal and reduce the opening error caused by signal drift or noise interference.
5. Optimize the working environment and media conditions
Keep the cleanliness of hydraulic oil in line with ISO 4406 standard, and prevent particles from entering the valve body; At the same time, ensuring the oil viscosity is within the recommended range is helpful to maintain the stability and repeatability of the spool movement.
IV. Conclusion
The accuracy of opening adjustment of proportional servo valve directly affects the overall control performance of hydraulic system. In practical application, closed-loop control, PID optimization, equipment calibration and environmental optimization should be combined to improve the adjustment accuracy. With the continuous improvement of industrial automation level, the technology of proportional servo valve is also improving, and its control accuracy will be more precise in the future, which will provide strong support for high-end equipment and intelligent manufacturing.