Servo valve is a key component in hydraulic servo system, which is widely used in industrial equipment with high precision and quick response. Among them, the Zero Lap servo valve is widely used because of its simple structure and fast response. The adjustment of zero-cover servo valve is a highly technical work, which is directly related to the control accuracy and dynamic performance of the system. Based on the structural principle, this paper discusses the adjustment method and matters needing attention of zero-cover servo valve.
First, the basic principle of zero cover servo valve
Zero-cover servo valve means that when in the neutral position, the opening between the valve core and the valve sleeve is zero, that is, there is no oil flow. This design can avoid median leakage and improve the control accuracy of the system. Servo valve drives electromagnetic coil by receiving control signal (usually current signal), and then controls the position of valve core to realize accurate control of hydraulic cylinder or motor.
Because of its structural characteristics, the zero-cover servo valve requires high control of the loop in the adjustment process, especially near the zero point, which is prone to dead zone or response delay, so special attention should be paid to the adjustment process.
Second, the preparation before the servo valve adjustment
Before adjustment, it must be confirmed that the system is in a stable state, including hydraulic oil pressure, temperature, oil cleanliness and other indicators that meet the requirements. In addition, relevant tools should be prepared, such as multimeter, oscilloscope, signal generator and servo amplifier.
Third, the adjustment steps
1. Zero calibration
-First, set the servo valve to the neutral position to ensure that the input signal is 0.
-Adjust the feedback device to make the valve core in the mechanical neutral position.
-Use a multimeter to detect whether the feedback voltage or current is 0. If there is any deviation, adjust the feedback potentiometer for correction.
2. Dead zone adjustment
-Input a small signal (for example, 1 mA) and observe whether the actuator responds.
-If there is no response, it means that there is a dead zone, so it is necessary to adjust the bias or spool position of the servo amplifier to reduce the dead zone.
3. Gain adjustment
-The gain determines the sensitivity of the servo valve to the input signal.
-On the premise of stable operation of the system, gradually increase the gain until the system slightly oscillates, and then adjust it appropriately to obtain the best response speed and stability.
4. Frequency response test
-Use a signal generator to apply input signals with different frequencies and observe the system response.
-Analyze the response curve by oscilloscope to judge whether the servo valve meets the dynamic performance requirements of the system.
5. Closed-loop regulation
-In the closed-loop control system, combined with the controller parameters (such as PID parameters) for joint adjustment, to ensure the stability and accuracy of the whole system.
Four, adjust the matters needing attention
-Anti-static equipment should be worn during adjustment to prevent damage to electronic components inside the servo valve;
-During debugging, the system should be operated step by step to avoid the system out of control due to excessive one-time adjustment;
-The cleanliness of the oil must meet NAS level 7 or above to prevent impurities from blocking the valve core;
-If there is oscillation or abnormal noise in the system, stop debugging immediately and investigate the causes.
tag
The adjustment of zero-cover servo valve is a job with strong professionalism and high technical requirements. In order to ensure the stability and control accuracy of the servo system, theoretical knowledge and practical experience should be combined in the adjustment process, and the operation procedures should be strictly followed. Only on the basis of correct adjustment can we give full play to the performance advantages of servo valve and improve the operating efficiency and reliability of the whole hydraulic system.