Slide valve servo valve is a key control component in hydraulic system, which is widely used in high-precision and high-response hydraulic servo control systems, such as aerospace, robots, CNC machine tools and other fields. Its core function is to adjust the flow direction and flow rate of hydraulic oil by controlling the displacement of the slide valve, so as to realize accurate control of the position, speed and force of the actuator (such as hydraulic cylinder or hydraulic motor). This paper will discuss how to realize the accurate control of the flow rate of the slide valve servo valve from the aspects of structural principle, control mechanism and application characteristics.
First, the basic structure and working principle of
slide valve servo valve
Slide valve servo valve is mainly composed of slide valve, electromagnetic torque motor (or proportional electromagnet), feedback mechanism and valve body. Among them, the slide valve is the core component to control the oil flow, usually with multi-shoulder structure. Through its axial movement in the valve body, the on-off relationship and opening area between oil ports are changed, and then the flow size and direction are controlled.
The work of the servo valve is based on the “displacement-flow” control principle: when the input electric signal acts on the electromagnetic torque motor, the electromagnetic force generated makes the slide valve core slightly displace. This displacement of the slide valve changes the opening of the valve port, thus controlling the oil flow into the actuator. The position of the slide valve is proportional to the input signal, so continuous and accurate flow regulation can be realized.
Second, the flow control mechanism analysis
The key to control the flow of slide valve servo valve lies in the relationship between its opening and pressure difference. According to the basic
formula of fluid mechanics:
$$ Q = C_d cdot A cdot sqrt{frac{2Delta P}{
ho}} $$
Where q is the flow rate, Cd is the flow coefficient, A is the flow area of the valve port, δ P is the pressure difference between the two sides of the valve port, and ρ is the oil density.
As can be seen from the formula, when the pressure difference ΔP remains constant, the flow rate Q is mainly determined by the valve port area A; The valve port area a is determined by the displacement of the slide valve. Therefore, the linear control of output flow can be realized by controlling the displacement of the slide valve.
In addition, the servo valve is usually equipped with a feedback device (such as mechanical feedback or electrical feedback) to feed back the actual position of the slide valve to the controller to form a closed-loop control loop, so as to ensure that the displacement of the slide valve is consistent with the input signal and improve the control accuracy and response speed.
Third, the application advantages of slide valve servo valve in the system
1. High responsiveness: Due to its light weight and short stroke, the slide valve can quickly respond to command signals, which is suitable for occasions with high dynamic performance requirements.
2. High-precision control: the closed-loop feedback mechanism makes the position control of the slide valve very accurate, which can realize micron-level positioning.
3. Independent control of flow and pressure: By cooperating with pressure compensator, constant flow control can be realized, which is not affected by load change.
4. Multi-level control can be realized: it is suitable for proportional control and servo control to meet various control requirements under complex working conditions.
IV. Conclusion
To sum up, the spool servo valve plays an important role in modern hydraulic control system with its advantages of compact structure, rapid response and high control accuracy. It realizes efficient and accurate control of flow through fine adjustment of slide valve displacement, which provides a solid technical foundation for realizing high-performance hydraulic servo system. With the continuous progress of control theory and manufacturing technology, spool servo valve will play a more important role in future industrial automation and intelligent manufacturing.