Aircraft Brake Pressure Control Using Axle Acceleration Feedback
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Solution Overview
Problem
Aircraft braking systems face challenges in controlling brake pressure during low-speed operations, where wheel speed signals become unreliable, leading to oscillations, noise, and discomfort, and existing systems lack effective mechanisms to manage abrupt brake applications.
Innovation Solution
A brake control system that includes an accelerometer coupled to an axle, a servo valve, and a brake control unit that adjusts braking command pressure based on axle acceleration, switching to pedal command pressure when necessary, and monitors brake pedal position to manage pressure effectively, thereby mitigating oscillations and ensuring safe braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed feedback signals are used for antiskid control, then wheel locking prevention is achieved, but the system becomes unreliable at low speeds due to signal unreliability
Solution Approach 1:
The patent replaces the unreliable wheel speed sensor feedback system with an accelerometer-based mechanical detection system. The accelerometer directly measures axle acceleration to detect skid conditions, eliminating dependence on unreliable wheel speed signals at low speeds. This substitution maintains antiskid control functionality while resolving the measurement reliability issue.
Solution Approach 2:
The patent changes the control parameter from wheel speed to axle acceleration. By using acceleration feedback instead of speed feedback, the system achieves reliable skid detection at low speeds where wheel speed signals become unreliable. The brake control unit processes acceleration signals to generate appropriate brake pressure commands, maintaining control reliability across all speed ranges.
2Force
If brake pressure is increased to improve stopping performance, then deceleration capability is enhanced, but oscillations and noise increase causing discomfort
Solution Approach 1:
The patent implements a feedback control system using accelerometer data to monitor axle acceleration in real-time. When skid detection occurs or oscillations are detected, the system provides feedback to the brake control unit, which then adjusts brake pressure accordingly. This closed-loop feedback prevents excessive brake force application and eliminates oscillations and noise while maintaining effective stopping performance.
Solution Approach 2:
The patent dynamically adjusts brake pressure based on real-time acceleration feedback rather than applying fixed pressure. The system modulates brake force according to actual wheel/axle conditions, increasing pressure when needed for stopping and reducing it when oscillations occur. This dynamic control eliminates harmful oscillations and noise while preserving deceleration capability.
3Loss of time
If abrupt brake applications are made to improve response time, then stopping distance is reduced, but system stability deteriorates due to oscillations
Solution Approach 1:
The patent applies preliminary gentle brake pressure before full braking force is needed. The accelerometer-based system detects early signs of skid or oscillation conditions and preemptively adjusts pressure to prevent instability. This preliminary action maintains system stability while still achieving rapid response, as the system is already prepared and adjusting pressure smoothly rather than applying abrupt force.
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 system effectively limits or eliminates oscillations, reduces noise and discomfort, and ensures safe braking by dynamically adjusting brake pressure in response to axle acceleration and pedal input, enhancing the reliability and safety of aircraft braking systems.
Implementation Method 1
an accelerometer coupled to an axle, a servo valve configured to receive a hydraulic fluid and provide the hydraulic fluid to apply a braking force to a wheel via a hydraulic line, and a brake control unit in electronic communication with the servo valve. The brake control unit is configured to receive an axle acceleration signal indicative of an axle acceleration from the accelerometer
Implementation Method 2
a servo valve configured to receive a hydraulic fluid and provide the hydraulic fluid to apply a braking force to a wheel via a hydraulic line
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A brake control system of the present disclosure includes an accelerometer (175) coupled to an axle (170). A brake control unit (150) is configured to receive an axle acceleration signal indicative of an axle acceleration from the accelerometer (175), and decrease a braking command pressure in response to the axle acceleration being greater than a threshold acceleration value.