Acoustic Airspeed Sensor Using MEMS Microphones
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Solution Overview
Problem
Conventional airspeed sensors face challenges such as icing issues, mechanical moving parts, and airflow obstruction, which affect accuracy and reliability, especially at high speeds and in icing conditions.
Innovation Solution
An acoustic airspeed sensor system using a ring of microelectro-mechanical systems (MEMS) microphones around a transmitter to measure time-of-flight of acoustic pulses, determining wind angle and airspeed without mechanical parts or obstructing airflow, and incorporating a method to ignore shadowed receivers to improve data accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pitot-static probes are used to measure airspeed, then airspeed measurement is achieved, but the system is subject to failures due to icing and heater failures
Solution Approach 1:
The patent replaces the mechanical pitot-static probe system with an acoustic measurement system using ultrasonic transducers. The airspeed is measured by timing acoustic pulses traveling with and against the airflow, eliminating mechanical components that are susceptible to icing and mechanical failures.
Solution Approach 2:
The patent uses acoustic waves (sound pulses) propagating through the air to measure airspeed. By measuring the time of flight of acoustic pulses in the direction of airflow and opposite to it, the system derives airspeed without mechanical contact with the flow, avoiding icing accumulation on sensing surfaces.
2Measurement precision
If the probe faces directly into the air flow to measure stagnation pressure, then airspeed measurement is enabled, but icing tends to accumulate where air flow stagnates
Solution Approach 1:
The patent replaces the stagnation pressure measurement approach with acoustic time-of-flight measurement. Ultrasonic transducers emit acoustic pulses that travel through the airflow, and the time taken for these pulses to reach receivers upstream and downstream is measured. This eliminates the need for a probe facing directly into the flow, preventing stagnation points where icing would accumulate.
3Measurement precision
If ultrasonic anemometers use transducer supporting structure to measure air velocity, then air speed measurement is achieved, but the flow is distorted by the transducer supporting structure
Solution Approach 1:
The patent extracts the transducers from their traditional mounted configuration and embeds them flush with the aircraft surface. This removes the supporting structure that would otherwise protrude into the airflow and cause distortion, allowing the airflow to remain undisturbed while still enabling acoustic measurements.
Solution Approach 2:
The patent transitions from a configuration where transducers are mounted on supporting structures extending into the flow to a flush-mounted configuration where transducers are embedded in the aircraft surface. This dimensional change eliminates the protruding structure that causes flow distortion while maintaining the acoustic measurement capability.
4Ease of manufacture
If previous flush mounted systems used sensors upstream and downstream of a sound transmitter, then airspeed measurement was attempted, but power was required to get a signal to propagate upstream
Solution Approach 1:
The patent changes the acoustic frequency parameter to use lower frequency sounds that can propagate upstream with less power requirement. By operating at frequencies where atmospheric attenuation is lower, the system enables upstream signal propagation without excessive power consumption, making flush-mounted operation practical.
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 solution provides high-bandwidth, high-update-rate measurements of wind angle and airspeed, reduces icing risks, and minimizes airflow disturbance and drag, enabling accurate air data sensing across a range of conditions without direct airflow exposure.
Implementation Method 1
They measure air speed based on the time of flight of sonic pulses between pairs of transducers
Implementation Method 2
measure air velocity. They measure air speed based on the time of flight of sonic pulses
Data Source
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AI summary
An acoustic airspeed sensor system (500) can include at least one acoustic transmitter (12) configured to provide an acoustic pulse (501), a plurality of acoustic receivers (14A-14L) including at least a first acoustic receiver (14A) positioned at a first radial distance from the at least one acoustic transmitter (12) and a second acoustic receiver (14B) positioned at a second radial distance from the at least one acoustic transmitter (12). The first acoustic receiver (14A) is configured to receive the acoustic pulse (501) at a first time and output a first receiver signal (503). The second acoustic receiver (14B) is configured to receive the acoustic pulse (501) at a second time and output a second receiver signal (505). The sensor system (500) can include an air data module (507) operatively connected to the first acoustic receiver (14A) and the second acoustic receiver (14B). The air data module (507) is configured to determine true air speed (TAS) based upon a first signal delay, a second signal delay, and a wind angle.