A high-temperature fuel flow regulating valve and its application method

Abstract

This invention discloses a high-temperature fuel flow regulating valve and its application method, relating to the field of flow regulating valve design. The high-temperature fuel flow regulating valve includes: a throttling piston assembled in the valve body and capable of bidirectional linear motion along the axial direction; a high-temperature fuel passage provided at the throttling end of the throttling piston in the valve body; solenoid valves I and II disposed on the valve body for controlling the upward and downward movement of the throttling piston; a cold oil passage disposed between the high-temperature fuel passage and the solenoid valves to construct a heat-insulating layer; a displacement sensor disposed in the middle of the valve body, with its detection end directly connected to the throttling piston to detect the axial displacement of the throttling piston in real time; and a controller communicatively connected to the displacement sensor and each solenoid valve. This invention achieves closed-loop control through dual solenoid valves and a displacement sensor, enabling real-time and precise adjustment of the throttling piston opening, effectively solving the technical problem of stable regulation and reliable control of fuel flow under high-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of flow control valve design. More specifically, this invention relates to a high-temperature fuel flow control valve and its application method. Background Technology

[0002] In ramjet engine power systems, precise regulation of high-temperature fuel flow is crucial for system combustion efficiency, operational stability, and thermal management control. Traditional flow regulation mechanisms often employ mechanical adjustment or single-drive methods, which suffer from slow response speed, low regulation accuracy, and insufficient reliability under high-temperature conditions, making it difficult to meet the real-time flow control requirements under complex and variable operating conditions. Furthermore, in high-temperature fuel environments, valves are susceptible to temperature and pressure fluctuations, leading to significant flow control deviations. Therefore, there is an urgent need for a high-temperature fuel flow regulating valve that is compact, responds quickly, and offers high control accuracy. Summary of the Invention

[0003] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0004] To achieve these objectives and other advantages of the present invention, a high-temperature fuel flow regulating valve is provided, comprising: A throttling piston assembled in the valve body and capable of bidirectional linear motion along the axial direction; The valve body is provided with a high-temperature fuel passage at the throttling end of the throttling piston; Solenoid valve I and solenoid valve II are mounted on the valve body to control the rising and falling motion of the throttling piston. A cold oil passage is installed between the high-temperature fuel passage and the solenoid valve to construct a heat-insulating layer. A displacement sensor is located in the middle of the valve body and its detection end is directly connected to the throttle piston to detect the axial stroke displacement of the throttle piston in real time. A controller that communicates with displacement sensors and various solenoid valves; The throttling piston has a tapered end that is directly opposite the throttling orifice of the high-temperature fuel passage. The flow rate of the high-temperature fuel passage is adjusted by changing the opening of the throttling orifice through axial displacement.

[0005] Preferably, the cold oil passage is configured as an annular closed flow channel surrounding the sidewall and bottom of the high-temperature fuel passage, and the cold oil passage completely covers the contact surface between the high-temperature fuel passage and the solenoid valve mounting location.

[0006] Preferably, a radial sealing ring is provided between the throttling piston and the inner wall of the valve body to prevent leakage of high-temperature fuel.

[0007] Preferably, the throttling piston is configured as a variable diameter structure, and the valve body is provided with a limiting step that mates with the variable diameter end face; The defined step and the variable diameter end face are connected by an elastic element.

[0008] Preferably, the lower end of the throttling piston is the driving end, and the driving end is flexibly connected to the driving rods of solenoid valve I and solenoid valve II.

[0009] A method for applying a high-temperature fuel flow regulating valve includes: When not in operation, the valve is de-energized, solenoid valve I is closed and solenoid valve II is open. Under the action of its own elastic force, the elastic element pushes the throttle piston to the lower limit position, so that the throttle port of the high temperature fuel passage is fully open, and the valve is in the maximum opening and maximum flow state to meet the large flow fuel supply demand. When in the working adjustment state, the valve is energized and room temperature cooling oil is introduced into the cold oil passage to build a heat insulation layer. The controller sends a corresponding control signal based on the set target flow parameters, and adjusts the throttle opening of the high temperature fuel passage by switching the working state of the corresponding solenoid valve. At the same time, the displacement sensor monitors the stroke of the throttle piston in real time until the throttle piston moves to the stroke corresponding to the target opening. In the power-off reset state, the valve is de-energized, solenoid valve I is in the closed state and solenoid valve II is in the open state. The throttling piston moves to the lower limit position under the action of the elastic element, and the valve returns to the maximum opening degree, completing the working cycle.

[0010] Preferably, in the working adjustment state, if it is necessary to reduce the flow rate, the controller issues command I to energize and open solenoid valve I and energize and close solenoid valve II. This allows fuel from the cold oil passage to enter the control chamber through solenoid valve I to increase the pressure inside the chamber, thereby driving the throttle piston to move upward axially against the force of the elastic element, thus reducing the opening of the throttle orifice in the high-temperature fuel passage. At the same time, the controller detects the upward stroke of the throttle piston in real time through a displacement sensor and drives the throttle piston to move up or down through a preset PID adjustment module in the controller until the throttle piston reaches the stroke corresponding to the target opening. Then, solenoid valve I is de-energized, and the throttle piston maintains its current position to complete the working state adjustment.

[0011] Preferably, during the adjustment process, if an increase in flow rate is required, the controller issues command II to energize and close solenoid valve I and open solenoid valve II. This allows fuel in the control chamber to be discharged through solenoid valve II, reducing the pressure within the chamber. Meanwhile, the throttle piston moves axially downward under the action of the return spring, increasing the opening of the throttle port in the high-temperature fuel passage. Simultaneously, the controller uses a displacement sensor to detect the downward stroke of the throttle piston in real time and drives the throttle piston to move up or down through a preset PID control module until the throttle piston reaches the stroke corresponding to the target opening. At this point, solenoid valve II is energized and closed, and the throttle piston maintains its current position, completing the adjustment of the working state.

[0012] Preferably, the control equation of the PID control module is represented by the following formula: In the above formula, x aim The preset stroke target for the throttling piston, x ( t This represents the real-time stroke data of the throttling piston. e ( t This represents the travel deviation. k 1 represents the speed coefficient of the upward movement of the throttling piston controlled by solenoid valve I. k 2 represents the speed coefficient of the downward movement of the throttling piston controlled by solenoid valve II. u 1( t This refers to the action of solenoid valve I. u 2( t This refers to the action of solenoid valve II; sign + ( u )express u If the value is greater than 0, it is set to 1; otherwise, it is set to 0. sign - ( u )express u If the value is less than 0, it is set to 1; otherwise, it is set to 0. k p , k i , k d These are the corresponding gain coefficients. This represents the dynamic relationship of the throttling piston displacement when each solenoid valve is activated.

[0013] The present invention has at least the following beneficial effects: Firstly, this invention can protect precision components through efficient heat insulation. Specifically, through the dynamic heat insulation design of the cold oil channel, it completely blocks the heat transfer from 1000K high-temperature fuel to the solenoid valve and displacement sensor, avoiding high-temperature failure of electronic control components and aging of seals. Compared with conventional regulating valves, it has improved high-temperature resistance, extended valve service life, and significantly reduced safety hazards.

[0014] Secondly, this invention achieves high stability of flow control through closed-loop precise regulation. Specifically, during operation, a closed-loop control mode with real-time feedback from displacement sensors and dual control of solenoid valves is adopted to eliminate flow deviations caused by thermal deformation of the high-temperature valve body and fluctuations in the medium. The valve flow regulation accuracy reaches ±1%, realizing stepless precise regulation of high-temperature fuel flow, which fully meets the fine regulation requirements of high-end power systems.

[0015] Third, the invention has a large flow rate in the non-working state, which makes it more adaptable. That is, the return spring drives the throttle piston to the lower limit maximum opening position, and the flow rate reaches the maximum value in the non-working state. This can meet the needs of special working conditions such as system startup and emergency oil supply, solve the problem of insufficient initial flow rate of conventional regulating valves, and has a wider range of applicable scenarios.

[0016] Fourth, the invention has a compact structure and high reliability. The overall structure of the invention is simple, without complex transmission mechanisms. It uses high-temperature resistant and deformation-resistant materials, is suitable for harsh working conditions of 1000K high temperature, and has high working stability. It can be applied to a variety of high-end fields such as aerospace, special industry, and high-temperature fuel test bench.

[0017] Fifth, the control response speed of the present invention is fast. That is, through the coordinated drive of two sets of solenoid valves and the real-time feedback of the displacement sensor, the throttle piston displacement response time is short and the valve opening is adjusted quickly. It can quickly adapt to the working condition changes of the high-temperature fuel system and improve the overall system performance.

[0018] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of the high-temperature fuel flow regulating valve of the present invention; Among them, high temperature fuel inlet-1, high temperature fuel outlet-2, cold oil inlet-3, solenoid valve I-4, solenoid valve II-5, displacement sensor-6, piston chamber-7, throttle piston-8, return spring-9, cold oil outlet-10, valve body-11, high temperature fuel passage-12, cold oil passage-13, throttle port-14, annular passage-15, branch passage-16, throttle end-17, drive end-18. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0021] A high-temperature fuel flow regulating valve includes: a valve body 11, a solenoid valve I 4, a solenoid valve II 5, a displacement sensor 6, an elastic element (i.e., a return spring 9), a throttle piston 8, and other components. The valve body 11 is designed with two independent flow channels, namely a high-temperature fuel channel 12 and a cold fuel channel 13. The high-temperature fuel channel has an L-shaped structure in space, with a high-temperature fuel inlet 1 on one side and a high-temperature fuel outlet 2 on the other side. A throttle port 14 with an irregular structure is provided at the turning point of the high-temperature fuel channel. The throttle piston 8 switches the throttle port opening by switching the position of its extension into the throttle port. Furthermore, the cold oil passage is positioned between the high-temperature fuel passage and the solenoid valve mounting location, and spatially forms an annular closed flow channel surrounding the high-temperature fuel passage (i.e., an annular channel 15 is provided near the high-temperature fuel passage, and the valve body 11 is provided with at least one cold oil inlet 3 that cooperates with the annular channel, and one side of the cold oil inlet 3 is adapted to the corresponding solenoid valve mounting location through a branch passage 16, and the branch passage 16 is connected to the external circulation equipment through the cold oil outlet 10 after flowing through the solenoid valve). After the room temperature cooling oil is introduced inside, it can block the heat of the 1000K high-temperature fuel from being transferred to the solenoid valve and displacement sensor 6 side, forming a thermal isolation structure between the high-temperature side and the electrical side. In practical applications, the displacement sensor 6 detects the axial stroke of the throttle piston in real time and feeds the signal back to the controller, thereby controlling the on / off state of the two sets of solenoid valves to achieve closed-loop precise regulation and control of the high-temperature fuel flow. Specifically, the high-temperature fuel flow regulating valve of the present invention includes: Valve body 11: Made of high-temperature resistant alloy material, it serves as the overall support and flow channel carrier. The internal design includes a high-temperature fuel passage and a cold oil passage. The high-temperature fuel passage is used to flow 1000K high-temperature fuel, while the cold oil passage is located between the high-temperature oil passage and the solenoid valve, forming a heat-insulating layer to overcome the problem of heat from 1000K high-temperature fuel being conducted to the solenoid valve and sensor side. Through structural design, effective heat insulation between the high-temperature side and the electronic control side is achieved, protecting precision control components and improving the valve's high-temperature lifespan and operational stability.

[0022] Furthermore, the cold oil passage is a closed annular flow channel that surrounds the sidewalls and bottom of the high-temperature fuel passage and completely covers the contact surface between the high-temperature fuel passage and the solenoid valve mounting location. Room-temperature cooling oil flows through the cold oil passage, forming a dynamic heat insulation barrier that prevents the heat from the 1000K fuel in the high-temperature fuel passage from being transferred to the solenoid valve side through heat conduction and radiation, thus preventing the solenoid valve and displacement sensor 6 from malfunctioning due to high temperatures. The inlet and outlet of the cold oil passage are respectively located on both sides of the valve body 11, enabling the circulation of cooling oil to continuously remove heat and ensure that the electronic control components remain within the allowable temperature range.

[0023] Throttling piston 8: It is assembled in the piston chamber 7 of the valve body 11 and can move in both directions along the axial direction. The outer wall of the throttling piston 8 is sealed to the inner wall of the valve body 11. The front end of the throttling piston corresponds to the throttling port of the high-temperature fuel passage. The opening of the throttling port is changed by axial displacement, thereby adjusting the flow rate of high-temperature fuel. The bottom of the throttling piston is connected to the return spring 9, and the return spring 9 provides the return driving force.

[0024] Furthermore, the throttle piston 8 is made of high-temperature resistant material, and a radial sealing ring (not shown) is provided between the throttle piston and the inner wall of the valve body 11 to prevent high-temperature fuel leakage. The upper end of the throttle piston is the throttle end 17, which adopts an acute-angled conical structure to match the throttle port of the high-temperature fuel passage; the lower end is the drive end 18, which is connected to the return spring 9 and the solenoid valve drive rod. The solenoid valve drive rod and the throttle piston are flexibly connected to avoid rigid impact causing displacement deviation of the throttle piston.

[0025] Return spring 9: One end is fixed to the bottom of valve body 11, and the other end is connected to the lower end face of throttle piston. In the non-working state, return spring 9 is in a naturally extended state, pushing throttle piston to the lower limit position. At this time, the high-temperature fuel passage throttle port is fully open, and the valve flow reaches the maximum.

[0026] Solenoid valves I4 and I5 are symmetrically mounted on valve body 11, located outside the cold oil passage, and have no direct contact with the high-temperature fuel passage. The two sets of solenoid valves control the rising and falling motion of the throttle piston, respectively. By alternately switching on and off, they drive the axial displacement of the valve, adjusting the valve opening. By switching the working states of solenoid valves I4 and I5, it can be ensured that the throttle piston is at its maximum opening position under the action of the return spring 9 when the valve is not in operation, meeting the high flow requirements during system startup and emergency conditions.

[0027] Displacement sensor 6: Installed in the middle of valve body 11, the detection end of displacement sensor 6 is directly connected to the throttle piston, which detects the axial stroke displacement of the throttle piston in real time, converts the displacement signal into an electrical signal and transmits it to an external controller. Through displacement sensor 6 and the built-in PID adjustment module in the controller, closed-loop precise adjustment of high-temperature fuel flow is achieved, which solves the defects of conventional regulating valve open-loop control, no stroke feedback and large flow deviation, and ensures the accuracy and stability of flow control under different working conditions.

[0028] Controller (not shown): This is an external control unit that receives feedback signals from displacement sensor 6, compares them with preset flow parameters, and outputs control commands to regulate the on / off states of solenoid valve I4 and solenoid valve II, forming a closed-loop control circuit. The closed-loop control logic of the controller is as follows: Displacement sensor 6 collects the stroke displacement of the throttle piston in real time, converts it into an electrical signal, and transmits it to the external controller. The controller has a built-in PID adjustment module that compares the real-time stroke data of the throttle piston with the stroke parameters corresponding to the preset valve opening (the preset valve opening is obtained by conversion to the preset stroke target of the throttle piston) and calculates the deviation. If the real-time stroke is less than the preset value, the controller controls solenoid valve I4 to be energized, driving the throttle piston to move upward and reducing the valve opening; if the real-time stroke is greater than the preset value, the controller controls solenoid valve II to be energized, driving the throttle piston to move downward and increasing the valve opening. Through continuous signal feedback and solenoid valve on / off adjustment, the precise positioning of the throttle piston stroke is achieved, thereby completing the closed-loop precise control of the high-temperature fuel flow.

[0029] Let the preset stroke target of the throttling piston be x aim The real-time stroke data of the throttle piston is x ( t If the travel deviation is... e ( t )for: The dynamic relationship of the throttling piston displacement when each solenoid valve is activated is as follows: in, k 1 represents the speed coefficient at which solenoid valve 1 causes the throttle piston to move upward. k 2 represents the speed coefficient at which solenoid valve 2 causes the throttle piston to move downward. u 1( t This is the action of solenoid valve 1. u 2( t () indicates that solenoid valve 2 is activated.

[0030] The goal of closed-loop control is to make the travel deviation approach zero, i.e. The governing equations can then be written as: in, x aim The preset stroke target for the throttling piston, x ( t This represents the real-time stroke data of the throttling piston. e ( t This represents the travel deviation. k 1 represents the speed coefficient of the upward movement of the throttling piston controlled by solenoid valve I. k 2 represents the speed coefficient of the downward movement of the throttling piston controlled by solenoid valve II. u 1( t This refers to the action of solenoid valve I. u 2( t This refers to the action of solenoid valve II; sign + ( u )express u If the value is greater than 0, it is set to 1; otherwise, it is set to 0. sign - ( u )express u If the value is less than 0, it is set to 1; otherwise, it is set to 0. k p , k i , k d These are the corresponding gain coefficients. This represents the dynamic relationship of the throttling piston displacement when each solenoid valve is activated.

[0031] An application method for a high-temperature fuel flow regulating valve includes: 1. In non-working state, the valve is de-energized, solenoid valve I is in the closed state and solenoid valve II is in the open state. Under the action of its own elasticity, the return spring pushes the throttle piston to the lower limit position, the high temperature fuel passage throttle port is fully opened, and the valve is in the maximum opening and maximum flow state, which meets the large flow fuel supply demand under system start-up, emergency and other working conditions.

[0032] 2. In the working adjustment state, the valve is powered on, and room temperature cooling oil is introduced into the cold oil passage to form a heat-proof insulation layer; the controller sets the target flow parameters, and the displacement sensor monitors the initial stroke of the throttling piston in real time and feeds it back to the controller; Specifically, when a flow reduction is required, the controller issues a command to energize and open solenoid valve I and energize and close solenoid valve II. Fuel from the cold oil passage enters the control chamber through solenoid valve I, increasing the pressure inside the chamber. This drives the throttle piston to overcome the spring force of the return spring and move axially upward, reducing the opening of the throttle orifice in the high-temperature fuel passage and decreasing the fuel flow. The displacement sensor monitors the upward stroke of the throttle piston in real time until it reaches the stroke corresponding to the target opening. Then, solenoid valve I is de-energized, and the throttle piston maintains its current position.

[0033] When an increased flow rate is required, the controller issues a command to energize and close solenoid valve I and energize and open solenoid valve II. Fuel in the control chamber is discharged through solenoid valve II, the pressure in the chamber decreases, and the throttle piston moves downward axially under the action of the return spring, expanding the opening of the high-temperature fuel passage throttle orifice and increasing the fuel flow rate. The displacement sensor detects the downward stroke of the throttle piston in real time until it reaches the stroke corresponding to the target opening. Then, solenoid valve II is energized and closed, and the throttle piston maintains its current position.

[0034] 3. In the power-off reset state, the valve is de-energized, solenoid valve I is in the closed state and solenoid valve II is in the open state. The throttle piston moves to the lower limit position under the action of the reset spring force, and the valve returns to the maximum opening degree, completing the working cycle.

[0035] Therefore, this invention can achieve closed-loop control through dual solenoid valves and displacement sensors, and can adjust the throttle piston opening in real time with precision, effectively solving the technical problem of stable regulation and reliable control of fuel flow under high temperature conditions.

[0036] The above solution is merely an illustration of a preferred example and is not limited thereto. When implementing this invention, appropriate substitutions and / or modifications can be made according to the user's needs.

[0037] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A high-temperature fuel flow regulating valve, characterized in that, include: A throttling piston assembled in the valve body and capable of bidirectional linear motion along the axial direction; The valve body is provided with a high-temperature fuel passage at the throttling end of the throttling piston; Solenoid valve I and solenoid valve II are mounted on the valve body to control the rising and falling motion of the throttling piston. A cold oil passage is installed between the high-temperature fuel passage and the solenoid valve to construct a heat-insulating layer. A displacement sensor is located in the middle of the valve body and its detection end is directly connected to the throttle piston to detect the axial stroke displacement of the throttle piston in real time. A controller that communicates with displacement sensors and various solenoid valves; The throttling piston has a tapered end that is directly opposite the throttling orifice of the high-temperature fuel passage. The flow rate of the high-temperature fuel passage is adjusted by changing the opening of the throttling orifice through axial displacement.

2. The high-temperature fuel flow regulating valve as described in claim 1, characterized in that, The cold oil passage is configured as an annular closed flow channel surrounding the sidewall and bottom of the high-temperature fuel passage, and the cold oil passage completely covers the contact surface between the high-temperature fuel passage and the solenoid valve mounting location.

3. The high-temperature fuel flow regulating valve as described in claim 1, characterized in that, A radial sealing ring is provided between the throttling piston and the inner wall of the valve body to prevent high-temperature fuel leakage.

4. The high-temperature fuel flow regulating valve as described in claim 1, characterized in that, The throttling piston is configured as a variable diameter structure, and the valve body is provided with a limiting step that cooperates with the variable diameter end face; The defined step and the variable diameter end face are connected by an elastic element.

5. The high-temperature fuel flow regulating valve as described in claim 1, characterized in that, The lower end of the throttling piston is the driving end, and the driving end is flexibly connected to the driving rods of solenoid valve I and solenoid valve II.

6. A method for applying a high-temperature fuel flow regulating valve, wherein the high-temperature fuel flow regulating valve as described in any one of claims 1-5 is characterized in that, include: When not in operation, the valve is de-energized, solenoid valve I is closed and solenoid valve II is open. Under the action of its own elastic force, the elastic element pushes the throttle piston to the lower limit position, so that the throttle port of the high temperature fuel passage is fully open, and the valve is in the maximum opening and maximum flow state to meet the large flow fuel supply demand. When in the working adjustment state, the valve is energized and room temperature cooling oil is introduced into the cold oil passage to build a heat insulation layer. The controller sends a corresponding control signal based on the set target flow parameters, and adjusts the throttle opening of the high temperature fuel passage by switching the working state of the corresponding solenoid valve. At the same time, the displacement sensor monitors the stroke of the throttle piston in real time until the throttle piston moves to the stroke corresponding to the target opening. In the power-off reset state, the valve is de-energized, solenoid valve I is in the closed state and solenoid valve II is in the open state. The throttling piston moves to the lower limit position under the action of the elastic element, and the valve returns to the maximum opening degree, completing the working cycle.

7. The application method of the high-temperature fuel flow regulating valve as described in claim 6, characterized in that, In the working adjustment state, if it is necessary to reduce the flow rate, the controller issues command I to energize and open solenoid valve I and energize and close solenoid valve II. This allows fuel in the cold oil passage to enter the control chamber through solenoid valve I, increasing the pressure inside the chamber. This drives the throttle piston to overcome the force of the elastic element and move upward axially, reducing the opening of the throttle orifice in the high-temperature fuel passage. At the same time, the controller uses a displacement sensor to detect the upward stroke of the throttle piston in real time and drives the throttle piston to move up or down through a preset PID adjustment module in the controller until the throttle piston reaches the stroke corresponding to the target opening. Then, solenoid valve I is de-energized, and the throttle piston maintains its current position, completing the working state adjustment.

8. The application method of the high-temperature fuel flow regulating valve as described in claim 6, characterized in that, In the working adjustment state, if it is necessary to increase the flow rate, the controller issues command II to de-energize and close solenoid valve I and de-energize and open solenoid valve II. This allows the fuel in the control chamber to be discharged through solenoid valve II to reduce the pressure in the chamber. Meanwhile, the throttle piston moves downward axially under the action of the return spring, increasing the opening of the throttle port in the high-temperature fuel passage. At the same time, the controller detects the downward stroke of the throttle piston in real time through the displacement sensor and drives the throttle piston to move up or down through the preset PID adjustment module in the controller until the throttle piston reaches the stroke corresponding to the target opening. Then, solenoid valve II is energized and closed, and the throttle piston maintains its current position to complete the working state adjustment.

9. The application method of the high-temperature fuel flow regulating valve as described in claim 7 or 8, characterized in that, The control equation of the PID control module is characterized by the following formula: In the above formula, x aim The preset stroke target for the throttling piston. x ( t This represents the real-time stroke data of the throttling piston. e ( t This represents the travel deviation. k 1 represents the speed coefficient of the upward movement of the throttling piston controlled by solenoid valve I. k 2 represents the speed coefficient of the downward movement of the throttling piston controlled by solenoid valve II. u 1( t This refers to the action of solenoid valve I. u 2( t This refers to the action of solenoid valve II; sign + ( u )express u If the value is greater than 0, it is set to 1; otherwise, it is set to 0. sign - ( u )express u If the value is less than 0, it is set to 1; otherwise, it is set to 0. k p , k i , k d These are the corresponding gain coefficients. This represents the dynamic relationship of the throttling piston displacement when each solenoid valve is activated.

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