Hybrid Landing Gear Actuator With Reversible Pump Retraction
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Solution Overview
Problem
Current linear actuators for aircraft landing gear lack efficient mechanisms for controlled retraction and extension, particularly in scenarios where power availability is uncertain, leading to potential mechanical stress and safety concerns.
Innovation Solution
A hybrid hydraulic-electromechanical actuator with a normally open bypass valve and a dual-gear external gear pump driven by an electric motor, integrated with a planetary gear assembly, allowing for controlled fluid flow and piston translation, enabling both active and passive retraction and extension of landing gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hybrid hydraulic-electromechanical actuator is used, then controlled retraction and extension is achieved, but device complexity increases
Solution Approach 1:
The patent combines hydraulic and electromechanical systems into a single hybrid actuator unit. The electric motor drives the gear pump which pressurizes hydraulic fluid to move the piston, merging two separate systems (electromechanical motor-gearbox and hydraulic cylinder) into one integrated device that provides controlled motion while maintaining the benefits of both systems
Solution Approach 2:
The actuator serves multiple functions: the electric motor can drive the pump for active extension, the pump can operate in reverse for active retraction, and the bypass valve enables passive retraction through gravity. This multi-functionality reduces the need for separate actuators for different operations, offsetting the complexity increase with operational versatility
2Ease of operation
If a bypass valve is normally open, then fluid flows freely between chambers, but controlled retraction becomes difficult
Solution Approach 1:
The bypass valve transitions from a static always-open state to a dynamic controllable state. When the motor reverses rotation, the valve automatically closes to prevent bypass flow, enabling controlled retraction. This dynamic behavior allows the system to adapt its fluid flow characteristics based on operational requirements, providing both free flow when needed and controlled flow when needed
3Reliability
If the pump operates in reverse, then active retraction is enabled, but energy consumption increases
Solution Approach 1:
The system uses passive retraction through gravity when possible, requiring only partial motor intervention ( merely controlling the bypass valve closure) rather than full active retraction. This partial action approach consumes significantly less energy while still achieving the retraction function, reserving full motor-powered active retraction for situations where gravity alone is insufficient
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
The hybrid actuator ensures smooth and controlled operation of landing gear, reducing mechanical stress and enhancing safety by allowing fluid flow even in de-energized states and providing efficient energy use through reversible pump operation.
Implementation Method 1
a bypass valve (119) configured to control flow of the hydraulic fluid through the bypass channel (118)
Implementation Method 2
an electric motor (128) housed within the piston (120) and configured to drive the pump (126)
Implementation Method 3
a planetary gear assembly (127) housed within the piston (120) and coupled between the electric motor (128) and the pump (126)
Implementation Method 4
the pump pressurizes the pressure chamber (116), thereby causing a corresponding translation of the piston (120) to extend the piston (120)
Data Source
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AI summary
A hybrid actuator (100), having a central longitudinal axis (105), may include a housing (110) defining a central cavity (112). The hybrid actuator (100) may also include a piston (120) disposed within the central cavity (112), the piston (120) comprising a piston head (122) that divides the central cavity (112) into a pressure chamber (116) and an annular chamber (114). The piston (120) houses a pump (126) configured to pump fluid through a port (123) defined in the piston head (122) between the annular chamber (114) and the pressure chamber (116) to extend a piston rod (124) of the piston from the central cavity (112), according to various embodiments.