Electro-hydraulic servo valve (EHSV) is a key component in modern hydraulic control system, which is widely used in aerospace, industrial automation, robotics and other fields. It can convert electrical signals into hydraulic output and realize high-precision control of actuators (such as hydraulic cylinders or hydraulic motors). In order to achieve higher control accuracy and system stability, closed-loop control strategy is usually used to adjust the servo valve feedback.
First, the basic structure and working principle of electric feedback servo valve
The electric feedback servo valve is composed of electromagnetic coil, torque motor, slide valve and feedback mechanism. Its working principle is to control electromagnetic force by inputting current signal, so as to drive the slide valve to move and change the direction and flow rate of liquid flow. The electric feedback mechanism refers to the feedback of the actual displacement of the spool to the controller in the form of electrical signals, so as to realize the comparison and correction with the input instructions.
Second, the basic concept of closed-loop control
Closed-loop Control means that the system output is fed back to the input end, compared with the target value to generate an error signal, and the control signal is adjusted accordingly to make the output closer to the expected value. This control method can effectively suppress the disturbance and improve the response accuracy and stability of the system.
Third, the closed-loop implementation of electric feedback servo valve
1. Sensor feedback mechanism
Electric feedback servo valves usually have built-in displacement sensors (such as LVDT, linear variable differential transformer) to detect the real-time position of the spool. The sensor converts the spool position into a voltage signal, which is sent to the controller as a feedback signal.
2. Comparison and adjustment of controllers
The controller (such as PID controller) compares the given reference signal with the actual feedback signal, calculates the error and generates the corresponding control signal, and adjusts the current input to the servo valve to make the spool position close to the set value.
3. Dynamic response and stability optimization
In the closed loop, the dynamic performance (such as response speed, overshoot) and stability (such as anti-interference ability) of the system can be optimized by adjusting the controller parameters. Advanced control algorithms such as PID control, fuzzy control or adaptive control can further improve the system performance.
4. External feedback and multi-loop control
In addition to the electrical feedback of the valve core itself, sometimes external feedback (such as load position and speed feedback) is introduced to form a multi-loop control structure. For example, the inner ring controls the position of the valve core and the outer ring controls the position or speed of the actuator, forming a composite closed-loop system to improve the overall control accuracy.
Fourth, the advantages of closed-loop control
-High-precision control: the error is corrected by real-time feedback, and the control precision of the servo valve is significantly improved.
-Strong anti-interference ability: the influence of external disturbance on the system can be effectively suppressed through feedback adjustment.
-Fast dynamic response: The closed-loop system can track the changes of input instructions faster and improve the response speed.
-Strong adaptability: Combined with modern control theory, the closed-loop system can meet the control requirements under complex working conditions.
V. Application examples
In the flight control system of aircraft, the closed-loop control of electric feedback servo valve is used to accurately control the position of rudder surface; In industrial robots, it is used to achieve high-precision positioning of joint motion. In addition, it is also widely used in hydraulic test equipment, precision machine tools and other fields.
VI. Summary
By introducing closed-loop control, the electric feedback servo valve not only improves its dynamic performance and control accuracy, but also enhances the stability and adaptability of the system. With the development of sensor technology and control algorithm, the future closed-loop servo system will be more intelligent and efficient, which will provide stronger support for high-precision hydraulic control.
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