Magnetic Hold Brake for Aircraft PDU Power-Off Cargo Control
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Solution Overview
Problem
Existing cargo loading systems for aircraft face challenges in maintaining control over unit load devices (ULDs) during power disturbances, where PDUs either fully brake or allow ULDs to freely roll, lacking a reliable braking mechanism that functions independently of power supply.
Innovation Solution
A power drive unit (PDU) with a magnetic hold brake system, comprising a wheel, armature, brake pad, hold solenoid, release solenoid, and biasing member, which applies a hold braking force via magnetic flux to resist wheel rotation and a drag braking force when power is absent, ensuring controlled movement of ULDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PDU operates in a fully braked state to prevent ULD movement, then cargo control is improved, but the ULD cannot be manually pushed off the PDU
Solution Approach 1:
The brake system transitions from static (fully braked or fully released) to dynamic by introducing a drag brake state that provides continuous adjustable braking force. The biasing member maintains constant drag braking force on the armature, allowing the system to adapt between hold braking (when power is available) and drag braking (when power is lost), enabling both secure cargo holding and manual ULD movement capability.
2Ease of operation
If a PDU operates in an open state to allow free ULD movement, then ease of operation is improved, but the ULD may freely roll across the PDU without control
Solution Approach 1:
The biasing member (spring) provides self-service by automatically maintaining drag braking force on the armature regardless of power supply status. This passive mechanical system ensures that even when electrical power is lost, the brake system continues to provide controlled resistance to ULD movement, preventing uncontrolled rolling while still allowing manual pushing of cargo.
3Ease of operation
If a PDU operates in a drag state to allow manual ULD pushing, then ease of operation is improved, but the ULD movement is not fully controlled during power disturbances
Solution Approach 1:
The biasing member is pre-configured to maintain constant drag braking force that prepares the system for power disturbances. This pre-established mechanical braking force acts as a cushion against uncontrolled movement, ensuring that when power is lost, the transition to drag brake state is immediate and controlled, preventing sudden ULD acceleration or uncontrolled rolling.
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 PDU effectively resists wheel rotation with a strong hold braking force and provides a low drag braking force when power is off, allowing controlled movement of ULDs without manual assistance, reducing the need for passive braking rollers and ensuring safe cargo handling.
Implementation Method 1
The hold solenoid is configured to compress the armature against the brake pad by applying a first magnetic flux to the armature to compress the brake pad between the armature and the hold solenoid
Implementation Method 2
the release solenoid is configured to apply the force to separate the armature from the brake pad by applying a second magnetic flux to the armature to urge the armature away from the brake pad
Implementation Method 3
a biasing member configured to compress the armature against the brake pad by a drag amount that is less than the brake amount in order to apply a drag braking force to the wheel by resisting rotation of the armature
Data Source
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AI summary
A PDU for use in an aircraft includes a wheel (51, 52) configured to convey cargo through a portion of the aircraft. The PDU further includes an armature (108) rotatably coupled to the wheel (51, 52). The PDU further includes a brake pad (112). The PDU further includes a hold solenoid (114) configured to compress the armature (108) against the brake pad (112) by a brake amount in order to apply a hold braking force to the wheel by resisting rotation of the armature (108). The PDU further includes a release solenoid (120) configured to apply a force to separate the armature (108) from the brake pad (112) in order to allow the armature (108) to rotate. The PDU further includes a biasing member configured to compress the armature (108) against the brake pad (112) by a drag amount that is less than the brake amount in order to apply a drag braking force to the wheel (51, 52) by resisting rotation of the armature (108).