First, the basic working principle of servo valve
Servo valve is a high-precision control valve that controls the flow and direction of hydraulic oil according to the input electrical signal. Its core function is to convert weak electrical signals into corresponding hydraulic output, which has the characteristics of fast response, good dynamic performance and high control accuracy. The accuracy and stability of servo valve directly affect the performance of the whole hydraulic system.
Second, the purpose of calibration
During the use of servo valve, the performance may be degraded due to wear, pollution, temperature change and other reasons. The purpose of calibration is to detect the key performance parameters of the servo valve, ensure that its output characteristics meet the design requirements and ensure the stable operation of the system.
Third, the preparation work before calibration
1. Equipment preparation: including standard hydraulic source, signal generator, pressure sensor, flowmeter, data acquisition system, etc.
2. Environmental conditions: Ensure that the test environment is clean, the temperature is constant and there is no vibration interference.
3. State of calibrated valve: Check that the servo valve has no damage in appearance, no impurities inside and the coil connection is normal.
Fourth, the calibration process
1. Zero adjustment:
-When there is no input signal, adjust the zero position of the servo valve to ensure that the system has no offset output.
-Make the output flow zero or minimum through the mechanical zero or electrical zero in the regulating valve.
2. Static characteristic test:
-Input a series of standard current signals (such as 5 mA, ±10mA, etc.) and record the corresponding flow and pressure output.
-Draw the “input current-output flow” curve to check whether the linearity is good.
-Measure indicators such as hysteresis, repeatability and dead zone, and judge whether the static performance of the servo valve meets the standard.
3. Dynamic response test:
-Use a frequency generator to input sinusoidal signals with different frequencies and record the frequency response characteristics of the servo valve.
-Analyze the amplitude-frequency characteristics and phase-frequency characteristics of the servo valve, and evaluate its
dynamic response speed and stability.
4. Leak detection:
-In the closed state, detect the internal leakage between the chambers of the servo valve.
-If the leakage is too large, it may indicate that the valve core is worn or the seal is damaged and needs to be replaced or repaired.
5. Temperature rise test and long-term operation test:
-Check the temperature rise of the servo valve after long-term operation to ensure that the performance will not be affected by heat.
-Observe the stability of output characteristics during continuous operation.
V. Data Analysis and Calibration Report
All test data need to be systematically analyzed to determine whether the servo valve meets the factory standards or use requirements. After the calibration is completed, a detailed calibration report shall be issued, including test parameters, test results, conclusions and suggested measures.
VI. Matters needing attention
-Calibration should be carried out under the guidance of professionals to avoid equipment damage caused by misoperation;
-Use clean hydraulic fluid to prevent pollutants from entering the valve body;
-Records should be made before and after calibration, which is convenient for tracking the performance change trend of servo valve;
-For key applications (such as aerospace and military industry), it is recommended to calibrate regularly and establish a perfect maintenance system.
tag
Through the scientific calibration of the servo valve of the test bench, the control accuracy and operation stability of the hydraulic system can be effectively improved, the service life of the equipment can be prolonged, and a reliable basis can be provided for the subsequent fault diagnosis. With the improvement of automation, servo valve calibration technology is also developing constantly, and it will be more intelligent and standardized in the future. For engineers and technicians engaged in hydraulic system maintenance and testing, mastering the calibration method of servo valve is an essential professional skill.