Aircraft Landing Gear Bogie Pivot Positioning for Brake Torque Compensation
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Solution Overview
Problem
Conventional aircraft landing gear systems, particularly bogie anchored landing gears, do not effectively cancel brake torque during braking, leading to increased weight and complexity due to the need for compensating actuators, which can be bulky and heavy.
Innovation Solution
The aircraft landing gear assembly positions the bogie pivot closer to the rear axle than the front axle, utilizing a double-acting actuator that can apply forces to balance the system under braking, and is controlled to adjust forces based on brake torque and weight distribution, allowing for a smaller and lighter compensating actuator, and includes a configuration where brake assemblies are fixed to the axles to prevent rotation during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If brake assemblies are coupled to the main strut by brake rods in a bogie anchored landing gear, then the structure is simpler, but brake torque is transferred to the bogie beam causing instability
Solution Approach 1:
The brake torque compensation function is segmented from the brake assembly coupling structure. The brake assemblies remain coupled to the main strut via brake rods, while a separate compensating actuator is introduced to counteract the torque transferred to the bogie beam, thus maintaining structural simplicity while achieving stability.
Solution Approach 2:
A compensating actuator is introduced to apply a counteracting force to the bogie beam that balances the torque generated during braking. This counterforce compensates for the destabilizing effect of brake torque transfer, allowing the bogie anchored configuration to remain stable during braking operations.
2Stability of the object's composition
If a compensating actuator is added to a bogie anchored landing gear to prevent brake torque transfer, then bogie beam stability is improved, but the weight and size of the actuator must be sufficient to handle maximum braking loads
Solution Approach 1:
The compensating actuator is designed as a double-acting actuator that can dynamically adjust its output force based on real-time braking conditions. The controller modulates the actuator's force output to match the actual brake torque being applied, allowing the actuator to be sized for average rather than peak loads, thereby reducing its weight and size.
Solution Approach 2:
A control system continuously monitors the braking state and adjusts the compensating actuator's force output accordingly. This feedback control allows the actuator to provide only the necessary compensating force at any given moment, enabling the use of a smaller, lighter actuator that can handle variable loads through intelligent control rather than being oversized for maximum static loads.
3Stability of the object's composition
If the bogie pivot is positioned centrally between the axles, then the landing gear is balanced when stationary, but it becomes unbalanced during braking requiring a larger compensating actuator
Solution Approach 1:
The bogie pivot is positioned asymmetrically relative to the axle centers, specifically closer to one axle than the other. This asymmetric positioning creates an inherent balance that accounts for the torque distribution during braking, reducing the compensating force required from the actuator and allowing for a smaller, lighter actuator design.
Solution Approach 2:
The position parameter of the bogie pivot is optimized to achieve a balance between static stability and dynamic braking performance. By adjusting the pivot location along the bogie beam, the system achieves a configuration that minimizes the compensating actuator force requirement during braking, enabling weight reduction in the actuator.
4Weight of moving object
If a double-acting compensating actuator is used to apply variable forces during braking, then the actuator size can be reduced, but the control system complexity increases
Solution Approach 1:
The control system uses feedback from brake torque sensors to dynamically adjust the compensating actuator's force output. This feedback mechanism allows the system to maintain optimal balance with minimal actuator force, enabling the use of a smaller actuator while the control complexity is managed through straightforward force modulation based on measured braking conditions.
Data Source
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AI summary
An aircraft landing gear assembly (10, 50) comprising: a main strut having a mounting lug at one end region via which it is arranged to be pivotally coupled to an aircraft so as to be movable between a stowed condition for flight and a deployed condition for take-off and landing; an elongate bogie beam (14) comprising first and second end regions (14b) connected by a central body portion (14a) at which the bogie beam is pivotally coupled to the main strut via a bogie pivot pin (16); a first axle (22a) mounted at the first end region of the bogie beam, the first axle being arranged to carry one or more first wheel assemblies and first brake assemblies, each first brake assembly being attached to a brake rod which in turn is attached to the bogie beam; a second axle (22b) mounted at the second end region of the bogie beam, with the bogie pivot pin between the first and second end regions, the second axle being arranged to carry one or more second wheel assemblies and second brake assemblies; and a double acting actuator (24) coupled between the main strut and the bogie beam to apply a compressive or tensile force to the bogie beam, wherein the end regions of the bogie beam are arranged to position the bogie pivot axis (BP) below a plane (P2) intersecting the axes of rotation of the first and second wheel assemblies when the main strut is in the deployed condition.