Acoustic Vector Sensors Increasing UAV’s Situational Awareness

Document Number: 2009-01-3249

Date Published: November 2009

Author(s):
Hans-Elias DeBree - Microflown Technologies BV

Abstract:
Acoustic vector sensors (AVS), as they were recently developed based upon acoustic particle velocity sensors may improve the performance of Unmanned Aerial Vehicles (UAV) in terms of automatic take off and landing (ATOL), ground surveillance and mid air anti collision.

Any sound field can be described by both the scalar value sound pressure and the vector value acoustic particle velocity.

Only with the recent invention of the Microflown sensor, acoustic particle velocity in air has become a measurable quantity.

The combination of a sound pressure and three acoustic particle velocity sensors in one single node creates a broad-banded acoustic vector sensor that extends the audible range.

Whereas the concept of acoustic vector sensors is known in the radar community and for underwater acoustics, it was never applied in the air due to a lack of appropriate particle velocity sensors.

AVS offer a set of features that are complementary to other categories of sensors, such as radars, lasers and electro optical cameras.

AVS are passive, and their performance is not affected by adverse weather conditions like rain, clouds, fog, dust or a lack of daylight.

AVS cover the entire audible range and can detect sound sources without a line of sight, e.g., behind a mountain. The detection range may exceed ten kilometers.

For airborne applications in general, the low power consumption, the low weight and small footprint are of relevance.

Acoustic vector information can be obtained even in the presence of wind and background noise as generated by the airborne vehicle itself.

As AVS have a full and complete spherical field of detection, they can be used to cue narrow field of view sensors.

For automatic take off and landing purposes, completely sound-pressure-based acoustic detection systems on the ground were reported to be able to determine the geometric position of a helicopter with a high level of accuracy.

The deployment of AVS allows the integration of such a system on a lesser number of measurement nodes, whilst increasing the frequency range of the system and taking into account novel ground impedance modeling.

Successful tests were done on helicopters in 2008 and 2009.

For airborne-based ground reconnaissance, arrays of sound pressure transducers are traditionally used. Their frequency range is limited by their spacing, the outcome of all their signals combined one produces a single vector.

AVS are broad-banded, and each node itself already provides the full vector information. A collaborative mode only improves the accuracy of the information.

Civil aviation agencies put stringent requirements on the use of UAV in nonsegregated airspace.

As AVS provide in each node both amplitude and phase information, advanced signal processing techniques can be used to locate and track a large number of intruders in the "UAV bubble" simultaneously.

With four AVS, up to thirty broad-banded sound sources can be located and monitored simultaneously.

In this paper, both the performance of the AVS and novel-related signal processing routines will be discussed.

Results of simulations, laboratory and outdoor test results of this ongoing research will be presented.

File Size: 704K
Product Status: In Stock

See other papers presented at SAE 2009 AeroTech Congress & Exhibition, November 2009, Seattle, WA, USA, Session: Unmanned Aerial Systems - Safety, Certification and Standards (Part 1 of 2)

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