Variable Displacement Pump Feedback Control
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Solution Overview
Problem
Existing pump systems, particularly variable displacement pumps in aircraft fuel systems, face challenges in actively controlling output to pressure regulating valves due to insufficient response speed and lack of adjustability, especially during system disturbances.
Innovation Solution
A system comprising a variable displacement pump, a metering valve, a bypass line, a pressure regulating valve, a position sensor, and a control system, including an electrohydraulic servo valve, which measures and adjusts the pump displacement based on valve position feedback to control flow and pressure, utilizing a linear variable differential transformer (LVDT) for precise positioning and an electrohydraulic servo valve for actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If active pump displacement control is used to provide customized flow, then flow adjustability is improved, but control response speed deteriorates
Solution Approach 1:
The patent implements a feedback control system where a position sensor (LVDT) monitors the actual position of the pressure regulating valve piston and feeds this information back to the controller. The controller compares the actual position with the requested position and adjusts the electrohydraulic servo valve accordingly, creating a closed-loop control system that improves both response speed and positioning accuracy.
Solution Approach 2:
The patent replaces conventional mechanical control systems with an electrohydraulic control system. An electrohydraulic servo valve (EHSV) is used to control pump displacement based on electrical control signals from the controller, enabling faster and more precise control compared to purely mechanical systems while maintaining the hydraulic power transmission advantages.
2Device complexity
If conventional pressure regulating valve control is used, then system simplicity is maintained, but control precision deteriorates
Solution Approach 1:
A position sensor (LVDT) is integrated into the pressure regulating valve assembly to provide real-time feedback on piston position. This feedback mechanism enables precise measurement and control of valve position, transforming a simple open-loop control into a precise closed-loop control system while adding minimal complexity to the overall design.
Solution Approach 2:
The pressure regulating valve assembly is designed to perform multiple functions: it regulates pressure, provides position feedback through the integrated LVDT sensor, and works cooperatively with the electrohydraulic servo valve to control pump displacement. This multi-functionality reduces the need for separate components and maintains system simplicity.
3Stress or pressure
If bypass line is used to control pressure drop across metering valve, then pressure control is improved, but system complexity increases
Solution Approach 1:
The bypass line is integrated with the pressure regulating valve assembly, combining the pressure regulation function and the bypass flow control into a single coordinated system. The pressure regulating valve piston controls both the bypass flow and the actuation pressure for the electrohydraulic servo valve, merging multiple control functions into one mechanism.
Solution Approach 2:
The bypass line acts as an intermediary mechanism that controls the pressure drop across the metering valve by regulating the bypass flow. This intermediary control path enables precise pressure management without requiring direct control of the main fuel flow, simplifying the overall pressure control strategy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables faster and more adjustable control of pump output, enhancing the system's responsiveness and adjustability, thereby improving fuel flow management in aircraft fuel systems.
Implementation Method 1
The position sensor can include a linear variable differential transformer (LVDT) operatively connected between the piston and the valve housing to measure position of the piston relative to the valve housing.
Implementation Method 2
The control system can further include an electrohydraulic servo valve (EHSV) operatively connected to the controller and to the variable displacement pump to actuate an adjustment of displacement of the variable displacement pump in response to the control signal from the controller.
Data Source
Figure 1
Figure 2
AI summary
A system comprises a variable displacement pump (102), a metering valve (112), a bypass line (118), a pressure regulating valve (128), a position sensor (138), and a control system (140). At least one fuel nozzle (108) can be in fluid communication with the output line (114) downstream of the metering valve (112), wherein the variable displacement pump (102) is configured to supply fuel to the at least one fuel nozzle (108). The metering valve (112) can be disposed in the output line (114) for controlling outlet flow from the variable displacement pump (102). The system can also include an actuator line (124) parallel to the variable displacement pump (102) and connected to the output line (114) to provide actuation pressure from pump output of the variable displacement pump (102).