Aircraft Wheel Brake Modulated Fluid Control
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Solution Overview
Problem
Modern aircraft wheel brakes face challenges in precise control at low speeds, leading to erratic braking and diminished passenger comfort due to non-linear pressure control relationships, especially during taxiing and parking.
Innovation Solution
A system with normal and modulated operational modes, featuring a brake control valve and return valve that adjust fluid pressure to the wheel brake, providing a first portion of fluid back to the source in modulated mode to achieve improved deceleration control at low speeds, ensuring a more linear pressure increase and decrease for smoother braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large and robust wheel brakes are designed to handle worst case conditions with maximum brake pressure, then the braking capability in emergency situations is improved, but precise control at low speeds deteriorates due to non-linear pressure control relationships
Solution Approach 1:
The brake control system dynamically adjusts its characteristics based on operating conditions. The control valve provides non-linear pressure control at low speeds (modulated mode) for precise control, and linear pressure control at high speeds (normal mode) for maximum braking capability. This dynamic adaptation resolves the contradiction between precise low-speed control and high-speed braking performance.
Solution Approach 2:
The system changes the pressure control parameter characteristics based on speed conditions. At low speeds, the control valve creates a non-linear relationship between valve position and brake pressure to enhance control precision. At high speeds, it switches to a linear relationship for maximum braking force delivery. This parameter change allows the same brake system to excel at both low-speed precision and high-speed power.
2Force
If minimal pressure is applied to control the aircraft at low speeds, then the braking force required is reduced, but small changes in brake control valve positioning result in large changes in pressure provided to the wheel brakes causing erratic braking
Solution Approach 1:
The control valve modifies the pressure control parameter to create a non-linear relationship at low speeds. This means that small valve movements produce proportionally smaller pressure changes, maintaining control precision even when minimal braking force is required. The system effectively changes the sensitivity characteristic of the pressure control based on the operating regime.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor brake pressure and valve position, allowing it to compensate for the non-linear relationship. By actively adjusting valve positioning based on feedback from pressure sensors and speed sensors, the system maintains precise control throughout the entire pressure range, preventing erratic braking behavior.
3Ease of operation
If non-linear pressure control is used at low speeds, then precise control is improved, but passenger comfort deteriorates due to erratic braking
Solution Approach 1:
The system dynamically switches between two operational modes based on aircraft speed. In modulated mode (low speeds), it uses non-linear pressure control for precision. In normal mode (high speeds), it uses linear pressure control for comfort. This dynamic mode switching ensures that the harmful erratic braking effect only occurs when precision is needed at low speeds, and is suppressed when comfort is prioritized at higher speeds.
Solution Approach 2:
The control system changes the pressure-valve relationship parameter from non-linear to linear based on speed conditions. This parameter change eliminates the source of erratic braking (the non-linear amplification effect) when the aircraft is moving fast enough that precision is less critical and comfort becomes the priority.
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 enhances deceleration control at low speeds by adjusting fluid pressure in a linear manner, reducing erratic braking and improving passenger comfort during taxiing and parking operations.
Implementation Method 1
a fluid source configured to provide fluid in response to the brake actuation signal. The fluid has a first portion and a second portion. The system further includes, but is not limited to, a return valve in fluid communication with the fluid source, and configured to return the first portion of the fluid to the fluid source when the system is in the modulated operational mode
Data Source
AI summary
A system is provided having a normal operational mode and a modulated operational mode. The system includes an input device configured to generate a command signal. The system further includes a brake controller configured to generate a brake actuation signal in response to the command signal. The system further includes a fluid source configured to provide fluid in response to the brake actuation signal. The fluid has a first portion and a second portion. The system further includes a return valve in fluid communication with the fluid source, and configured to return the first portion of the fluid to the fluid source when the system is in the modulated operational mode. The system further includes a wheel brake in fluid communication with the fluid source and configured to engage a wheel of the aircraft in response to at least the second portion of the fluid.