Aircraft Brake Tachometer Layout for Low-Speed Sensing
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Solution Overview
Problem
Existing aircraft wheel tachometers face challenges with sensitivity at low speeds and are affected by temperature fluctuations, leading to reduced accuracy and increased risk of damage during wheel dismounting and re-mounting.
Innovation Solution
The proposed solution involves mounting the sensing component on the actuator support of the aircraft wheel and brake assembly, rather than inside the axle, allowing it to be less exposed to temperature cycles. This configuration is compatible with active sensors, such as Hall effect sensors, which offer better sensitivity than passive sensors. Additionally, the sensing component is no longer needed to be removed during wheel dismounting, reducing the risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If variable reluctance tachometers are used in the axle, then the structure is simple and robust, but the sensitivity at low speed is poor
Solution Approach 1:
The sensing component is extracted from the axle and relocated to the wheel cover, separating it from the harsh thermal environment while maintaining structural simplicity. This allows using more sensitive sensor types (Hall effect, optical) without compromising overall system robustness.
2Measurement precision
If Hall effect sensors are used, then the sensitivity at low speed is improved, but the sensitivity to temperature fluctuations increases
Solution Approach 1:
The sensing component is extracted from the axle (hot environment) and placed in the wheel cover (cooler environment), reducing thermal exposure. This enables using Hall effect sensors that are more sensitive to temperature, thereby improving low-speed measurement capability.
Solution Approach 2:
The sensing component is moved from a radial position (inside axle) to an axial position (in wheel cover), changing the spatial dimension of measurement. This dimensional shift places the sensor in a thermally more stable zone while maintaining measurement functionality.
3Device complexity
If the sensing component is installed inside the axle, then the structure is compact, but the risk of damage during wheel dismounting and re-mounting increases
Solution Approach 1:
The sensing component is extracted from the axle and integrated into the wheel cover, which remains on the aircraft during wheel maintenance. This eliminates the need to handle the sensitive sensor during wheel dismounting and re-mounting operations.
Solution Approach 2:
The sensing component is merged with the wheel cover structure, creating a single integrated unit. This ensures the sensor is never separated or handled during wheel maintenance, protecting it from damage while maintaining compact overall design.
4Duration of action of stationary object
If the sensing component is mounted on the actuator support in the wheel cover, then the lifetime is increased, but the device complexity increases
Solution Approach 1:
The wheel cover serves multiple functions: it protects the brake system, provides structural support, and now houses the sensing component. This multi-functionality increases lifetime by protecting the sensor while adding minimal complexity to the overall 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
This configuration enhances the accuracy of the aircraft wheel tachometer by reducing the impact of temperature fluctuations and increases the lifetime of the sensing component by minimizing handling-related damage.
Implementation Method 1
At low speed, their sensitivity is better than the sensitivity of variable reluctance tachometers. Nevertheless, the environment at the end of the axle is subjected to large temperature fluctuations associated with the temperature of the brake rising on landing, and with the temperature dropping in flight. Unfortunately, Hall effect sensors are more sensitive to the environment than are passive magnetic sensors.
Data Source
AI summary
An aircraft wheel and brake assembly includes a wheel, a brake configured to brake the wheel, and a measurement device configured to measure the speed of rotation of the wheel. The brake includes at least one friction member, an actuator support, and at least one brake actuator carried by the actuator support and configured to exert a braking force selectively on the friction member. The measurement device includes a target and a sensing component for producing a measurement signal representative of the speed of rotation of the target. The aircraft wheel and brake assembly is configured in such a manner that, when assembled, the target is constrained to rotate with the wheel and the sensing component is mounted on the actuator support. The target and the sensing component is configured in such a manner that the sensing component detects rotation of the target.