Aircraft Wheel Tachometer With Offset Hall Cells for Direction Detection
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Solution Overview
Problem
Conventional tachometers for aircraft wheels face issues with mechanical interference due to the required air gap for Hall effect measurement cells, which limits their accuracy and fails to determine the direction of rotation, especially during electric taxiing phases.
Innovation Solution
A contactless sensor with two offset Hall effect measurement cells is used, allowing for a larger air gap and increased target size, enabling higher frequency measurements and direction detection by combining signals from these cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single Hall effect measurement cell is used, then the device complexity is reduced, but the measurement frequency and direction detection capability are insufficient
Solution Approach 1:
The single measurement cell is segmented into two offset measurement cells arranged at different angular positions around the axis. Each cell independently generates measurement signals, enabling both higher measurement frequency through parallel operation and direction detection by comparing the phase relationship between the two signals.
Solution Approach 2:
The two offset measurement cells are merged into a single sensor assembly that functions as one integrated device. This combining approach increases measurement capability and frequency while maintaining a unified structural implementation, avoiding the need for completely separate sensor systems.
2Measurement precision
If the air gap between stator and rotor is reduced to improve measurement accuracy, then measurement precision is improved, but mechanical interference risk increases
Solution Approach 1:
The measurement system transitions from a single-point radial measurement to a multi-point angular distribution measurement. By arranging measurement cells at different angular positions around the axis, the system effectively utilizes the angular dimension to maintain measurement sensitivity while increasing the radial air gap distance, thereby reducing mechanical interference risk.
3Length of stationary object
If target size is increased to allow larger air gap, then the acceptable air gap is increased, but the number of targets must be reduced
Solution Approach 1:
The system compensates for the reduction in target quantity by utilizing the angular dimension through offset measurement cell arrangement. With fewer but larger targets, the offset cells ensure sufficient measurement sampling by being positioned at different angular locations, maintaining measurement frequency and accuracy despite having fewer targets.
Solution Approach 2:
Each measurement cell is positioned to optimally interact with specific targets at its local angular position. The offset arrangement ensures that each cell has its own set of targets to measure, effectively distributing the measurement function across different local regions around the axis, which compensates for having fewer total targets.
4Loss of information
If conventional single-cell Hall effect sensor is used, then device simplicity is maintained, but direction of rotation cannot be determined
Solution Approach 1:
The two measurement cells are positioned asymmetrically at different angular offsets around the axis rather than symmetrically or at the same position. This asymmetric angular arrangement creates distinct phase relationships between the signals from each cell that vary with rotation direction, enabling direction detection while maintaining a relatively simple dual-cell structure.
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 solution enhances measurement accuracy and frequency while reducing mechanical interference, allowing for reliable rotational speed and direction determination of aircraft wheels.
Implementation Method 1
The fixed part comprises a sensor having a single Hall effect measurement cell arranged to be positioned radially opposite magnetic targets borne by the rotating part
Data Source
AI summary
A tachometer for an aircraft wheel is mounted on an axle so as to rotate about an axis of rotation. The tachometer includes a stator intended configured to be secured to the axle and a rotor configured to be rotatably connected to the wheel. Either the stator or the rotor has at least one contactless sensor with at least two measurement cells adapted to interact with a plurality of targets borne by the other of the stator or the rotor in order to generate two signals representative of a rotational speed of the wheel. The measurement cells are angularly offset from one another about the axis so as to detect a direction of rotation of the wheel by combining the two signals.