Acoustic Angle-of-Attack Sensor Using Time-of-Flight
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Solution Overview
Problem
Angle-of-attack sensors are susceptible to failures due to ice buildup, which prevents the vane from rotating and provides incorrect values, and existing technologies obstruct airflow or use mechanical moving parts.
Innovation Solution
Acoustic angle-of-attack sensors that use a piezoelectric or MEMS speaker as a transmitter and microphones as receivers to measure time-of-flight, determining angle-of-attack without mechanical parts or obstructing airflow, employing polynomial fits and zero-crossing circuitry to calculate the angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vane-based angle-of-attack sensor is used, then the sensor can measure angle-of-attack by aligning with airflow, but ice buildup prevents the vane from rotating causing lockup and incorrect values
Solution Approach 1:
The patent replaces the mechanical vane-based sensing system with an acoustic measurement system using ultrasonic transducers. The angle-of-attack is determined by measuring the time-of-flight of acoustic signals between transducers mounted on the aircraft surface, eliminating mechanical moving parts that are susceptible to icing. This substitution of mechanical systems with acoustic fields resolves the contradiction by making the sensor immune to ice buildup while maintaining measurement capability.
Solution Approach 2:
The patent introduces acoustic signals as an intermediary medium to transfer information about airflow direction. Instead of directly mechanically aligning with airflow, the system uses acoustic wave propagation time as a mediator to indirectly measure angle-of-attack. This intermediary approach allows measurement without physical interaction between the sensor and airflow, preventing icing issues.
2Measurement precision
If traditional angle-of-attack sensors are used, then measurement can be obtained, but mechanical moving parts are present in the system
Solution Approach 1:
The patent eliminates mechanical moving parts by substituting them with acoustic transducers and electronic signal processing. The measurement precision is maintained through accurate time-of-flight measurement of acoustic signals, while the device complexity is reduced by removing motors, gears, and other mechanical components. The system uses fixed-mounted ultrasonic transducers that require no moving parts yet achieve precise angle-of-attack measurement.
3Measurement precision
If a vane-based sensor is used, then angle measurement is possible, but the vane obstructs airflow
Solution Approach 1:
The patent replaces the physical vane that obstructs airflow with acoustic transducers mounted flush on the aircraft surface. The acoustic waves propagate through the air without significant obstruction, allowing accurate time-of-flight measurement while minimizing disruption to the natural airflow pattern. This eliminates the harmful airflow obstruction caused by traditional vane structures.
Solution Approach 2:
The patent transitions from a one-dimensional vane alignment approach to a multi-dimensional acoustic field measurement approach. By using multiple transducers positioned at different locations and measuring the time-of-flight in three-dimensional space, the system determines angle-of-attack without requiring a physical vane to align with airflow, thus avoiding obstruction while maintaining measurement precision.
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
Enables accurate high-bandwidth angle-of-attack measurement without mechanical parts and reduces icing risks by not obstructing airflow, providing a reliable and efficient solution.
Implementation Method 1
the time-of-flight (t) of an acoustic pulse emitted by acoustic transmitter 12 can be measured to each of acoustic receivers 14A-14L
Implementation Method 2
where C0 is the speed of sound, a is angle-of-attack 20, and V is the airspeed of airflow 18
Data Source
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AI summary
An angle-of-attack sensor includes at least one acoustic transmitter is configured to provide an acoustic pulse. The first acoustic receiver is positioned at a radial distance from the at least one acoustic transmitter. The first acoustic receiver is configured to receive the acoustic pulse at a first time and provide a first receiver signal. The second acoustic receiver is positioned at the radial distance from the at least one acoustic transmitter aligned with an axis that extends through the at least one acoustic transmitter and the first acoustic receiver. The second acoustic receiver is configured to receive the acoustic pulse at a second time and provide a second receiver signal. The angle-of-attack circuitry is configured to determine a delay difference between the first and second receiver signals representative of a difference between the first time and the second time and determine an angle-of-attack based upon the delay difference.