As the core component of hydraulic control system, servo valve is widely used in industrial automation, aerospace, metallurgy, shipbuilding and other fields. Among them, position feedback servo valve has become an important part of high performance hydraulic system because of its high precision control ability and good dynamic response characteristics. In order to ensure the normal operation of the servo valve, its position feedback function must be accurately detected. This paper will introduce the basic principle of position feedback servo valve and its common detection methods.
First, the working principle of position feedback servo valve
The position feedback servo valve monitors the displacement of the spool in real time through the built-in position sensor (such as LVDT linear variable differential transformer), and converts the displacement signal into an electrical signal and feeds it back to the controller. According to the difference between the feedback signal and the target signal, the controller adjusts the input electrical signal to drive the spool to move, thus realizing the accurate control of the flow or pressure in the hydraulic system.
This closed-loop control mode enables the servo valve to automatically adjust the input according to the actual output, which improves the stability and accuracy of the system. Therefore, ensuring the accuracy and response speed of the position feedback signal is the key to the normal operation of the servo valve.
Second, the detection purpose of position feedback servo valve
The main purpose of testing the position feedback servo valve is:
1. Verify whether the electro-mechanical conversion function of the servo valve is normal;
2. Check whether the position sensor works normally and whether the feedback signal is accurate;
3. Confirm whether the closed-loop control performance of the system meets the design requirements;
4. Find potential faults in advance to prevent system failure.
Three, the common detection methods of position feedback servo valve
# 1. Static detection method
Static detection is carried out when the servo valve is not connected with hydraulic oil and only energized. By inputting a certain control current to the servo valve, the change of feedback voltage is observed and recorded. Under normal circumstances, the feedback voltage should change linearly with the input current. If there is nonlinearity, hysteresis or no feedback signal, there is a problem with the sensor or internal circuit.
# 2. Dynamic test method
The dynamic test is carried out after the servo valve is connected to the hydraulic system. By giving different input signals, the actual displacement response curve of the spool is observed and compared with the feedback signal. The parameters such as response time, overshoot and steady-state error can be analyzed by using oscilloscope and other equipment, so as to judge the working performance of servo valve.
# 3. Frequency response test
Frequency response test is one of the important means to evaluate the dynamic performance of servo valve. By applying sinusoidal signals with different frequencies, the amplitude-frequency characteristics and phase-frequency characteristics between the output and input of the system are measured. This is helpful to judge the bandwidth and response speed of servo valve, so as to evaluate its applicability under high frequency control.
# 4. Fault Diagnosis and Signal Analysis
Modern servo systems are usually equipped with digital controllers and fault diagnosis modules. By reading the error code, signal waveform and historical data inside the system, the problem can be quickly located. For example, if the feedback signal is lost or fluctuates violently, it may mean that the sensor is damaged or the line contact is poor.
Fourth, the detection matters needing attention
When testing the position feedback servo valve, the following points should be observed:
-Ensure that testing equipment (such as signal generator, oscilloscope, etc.) works normally;
-Avoid operating under high pressure and high temperature to avoid damaging the equipment;
-Be familiar with the technical parameters and wiring mode of the servo valve before testing;
-Comprehensive analysis of test results to avoid misjudgment of single data.
V. Conclusion
As a key component of high-precision hydraulic control system, the accuracy of position feedback servo valve directly affects the control effect of the system. Through scientific and reasonable detection methods, the state of the servo valve can be effectively evaluated, the system failure can be prevented, and the safe operation of the equipment can be guaranteed. With the development of intelligent control technology, the self-diagnosis and online monitoring ability of servo valve will be further improved, providing stronger technical support for industrial automation.