Landing Gear EHA Pressure Control to Prevent Pump Seizure
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Solution Overview
Problem
The Electro Hydrostatic Actuator (EHA) system for aircraft landing gear faces issues with hydraulic pump seizure when continuously operating under high loads, such as aerodynamic forces, which can hinder swift lifting of the leg.
Innovation Solution
The EHA system incorporates a control unit that monitors hydraulic pressure and pump revolution speed, stopping the electrically operated hydraulic pump when high pressure persists and resuming operation once pressure drops below a set threshold, along with the use of check valves to prevent backflow and ensure safe holding of the leg during lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electrically operated hydraulic pump is continuously operated under high load to swiftly complete lifting of the leg, then the lifting speed is improved, but the hydraulic pump may seize
Solution Approach 1:
The hydraulic pump operates intermittently rather than continuously. The control unit stops the pump when hydraulic pressure exceeds a set pressure threshold and resumes operation when pressure drops to or below a second set pressure threshold. This periodic operation pattern allows the pump to complete lifting swiftly when possible while preventing seizure by avoiding continuous high-load operation.
Solution Approach 2:
The system uses pressure sensors to continuously monitor hydraulic pressure and provides feedback to the control unit. Based on this feedback, the control unit dynamically adjusts pump operation - stopping when pressure is too high and resuming when pressure is sufficient - thereby resolving the contradiction between maintaining high lifting speed and preventing pump seizure.
2Reliability
If the hydraulic pump is stopped to prevent seizure, then the reliability is improved, but the lifting completion time increases
Solution Approach 1:
The system maintains continuity of the lifting function by automatically resuming pump operation when the resume condition is satisfied (hydraulic pressure drops to or below the second set pressure). This ensures that lifting continues without permanent interruption, minimizing time loss while preventing pump seizure during high-pressure periods.
Solution Approach 2:
The intermittent operation pattern allows the pump to rest periodically to prevent seizure while quickly resuming operation when conditions permit, thereby minimizing overall time loss. The periodic stop-and-resume cycle balances reliability protection with efficient lifting completion.
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 configuration allows for swift and safe lifting of the aircraft leg while minimizing the risk of hydraulic pump seizure, ensuring reliable operation and efficient fuel economy.
Implementation Method 1
an electrically operated hydraulic pump, comprising at an hydraulic pump driven by an electric motor, configured to supply a hydraulic fluid to the hydraulic actuator
Implementation Method 2
a pressure sensor attached to the hydraulic actuator or the hydraulic path and configured to output a measurement signal corresponding to a hydraulic pressure
Implementation Method 3
a sensor configured to output a measurement signal corresponding to a revolution speed of the hydraulic pump and/or the electric motor
Data Source
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AI summary
A landing gear lifting/lowering EHA system (10) includes: a hydraulic actuator (2) configured to lift and lower the leg of an aircraft; at least one electrically operated hydraulic pump (31, 32); a hydraulic path (101); a pressure sensor (38, 39) attached to the hydraulic actuator or the hydraulic path and configured to output a measurement signal corresponding to hydraulic pressure; and a controller (9) configured to output a control signal to the electrically operated hydraulic pump, wherein, when a state in which the hydraulic pressure exceeds a set pressure continues for a set time, the control unit stops the electrically operated hydraulic pump in operation and resumes the operation of the electrically operated hydraulic pump after the hydraulic pressure drops to or below a second set pressure after the electrically operated hydraulic pump is stopped.