Acoustic Sensors for Air and Surface Navigation Applications

IEEE/ION Position, Location and Navigation Symposium (PLANS), 2020

Current navigation sensors largely rely on electromagnetic signals to obtain position, velocity, and time (PVT) information. However, it can be observed that mammals like bats use acoustic waves, mostly ultrasound, for echolocation and relative navigation/collision avoidance purposes. Acoustic waves are also used by cetaceans like dolphins and sperm whales for echolocation. This paper investigates the performance of a novel acoustic positioning and navigation system (APNS) inspired by nature. Acoustic sensors have relatively lower cost, size, weight, and power (C-SWAP) and are easy to deploy. Additionally, being based on acoustic signals, this technique is immune to signal-in-space electromagnetic interferences. The attenuation of sound in air is discussed along with potential ranging errors and signal delays. A multistatic arrangement of sensors is discussed in detail, with an optimized arrangement of transmitters in a given test geometry. The transmitters broadcast their respective signals following a Time Division Multiple Access (TDMA) scheme. The receiver position is calculated based on ranging measurements from a minimum of three transmitters. The range is calculated based on the Time of Arrival (TOA) of acoustic waves from the transmitter to the receiver. The transmitters are arranged optimally to minimize Position Dilution of Precision (PDOP) as well as maximizing sensor availability. The error in positioning due to platform dynamics is also discussed. This analysis lead to an optimized arrangement of transmitters, thus supporting subsequent experimental activities.

1974

BMC Biology, 2022

Background Echolocating bats use echo information to perceive space, control their behavior, and adjust flight navigation strategies in various environments. However, the echolocation behavior of bats, including echo information, has not been thoroughly investigated as it is technically difficult to measure all the echoes that reach the bats during flight, even with the conventional telemetry microphones currently in use. Therefore, we attempted to reproduce the echoes received at the location of bats during flight by combining acoustic simulation and behavioral experiments with acoustic measurements. By using acoustic simulation, echoes can be reproduced as temporal waveforms (including diffracted waves and multiple reflections), and detailed echo analysis is possible even in complex obstacle environments. Results We visualized the spatiotemporal changes in the echo incidence points detected by bats during flight, which enabled us to investigate the “echo space” revealed through ec...

Proceedings of the 1998 Workshop on Autonomous Underwater Vehicles (Cat. No.98CH36290)

Acoustic (Hydroacoustic) position reference systems are used extensively within the Dynamic Positioning (DP) community. A clear understanding of the capabilities and limitations of these systems is required by all involved in the procurement, engineering and operation of DP vessels. The increase in the number of DP vessels working in close proximity and the increased water depths are just two of the factors driving the development of acoustic positioning systems. There are existing commercial sources that provide acoustic positioning systems with varying levels of capability as a Dynamic Positioning (DP) position reference sensor (PRS). Systems are currently available to provide a position reference to 12,000 feet of seawater (fsw) or 3,700m with an absolute accuracy of 3-5m and a relative accuracy of <2m. Also available from these and other sources are shorter range, higher resolution acoustic positioning systems. This paper discusses how these systems are configured and what capabilities they have. A definition of conventional systems and frequency bands is included. In addition to system types, some of the more common problems associated with acoustic positioning systems and some solutions to these problems are outlined. The paper concludes that although some systems, or components readily exist to provide reliable and repeatable position references, greater understanding during the specification and preliminary engineering stage of a DP vessel design and specification is required to achieve desired operational capabilities.

The Journal of the Acoustical Society of America, 2008

The biorobotic emulation of swimming and flying animals carrying out short-distance echolocation while maneuvering is considered. A simple and lightweight sonar for use on a small, maneuverable underwater vehicle for short-distance echolocation is explored. This sonar has four sensors and uses broadband, high-frequency signals to echolocate. The frequency-time characteristics of these signals are compared to those of bats and dolphins. The biosonar is paired with a biologically inspired, maneuverable, underwater vehicle, the combined use of sensors and maneuverability being analogous to animal behavior. Homing experiments have been carried out in an acoustic test facility where identification and localization of multiple targets is based on fusion of acoustic returns from multiple pings.

Forming part of a wider research programme that is studying the acoustics of bat echolocation, our work is focused on the development of an experimental method for the determination of the actual binaural signals generated during realistic echolocation conditions. Previous studies on the subject typically rely on simplified geometrical acoustics assumptions and hence predict the signals received by the bat as just delayed and attenuated versions of the emitted signal. We aim to surpass that by incorporating the physical acoustic properties of the emission and reception mechanisms as well as the backscattering properties of impulse response resulting from different echo generating objects in air. We present results from such measured responses and compare them with analytical predictions. We discuss the new possibilities opened for understanding the bat auditory processing capabilities when such detailed modelling of the actual input to the bat's auditory system is available. We also discuss the limitations associated with such air acoustic measurements over the very wide frequency bandwidth commonly used by many bat species.

SAE Technical Paper Series, 2009

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.

Sensors

This paper addresses some of the existing research gaps in the practical use of acoustic waves for navigation of autonomous air and surface vehicles. After providing a characterisation of ultrasonic transducers, a multistatic sensor arrangement is discussed, with multiple transmitters broadcasting their respective signals in a round-robin fashion, following a time division multiple access (TDMA) scheme. In particular, an optimisation methodology for the placement of transmitters in a given test volume is presented with the objective of minimizing the position dilution of precision (PDOP) and maximizing the sensor availability. Additionally, the contribution of platform dynamics to positioning error is also analysed in order to support future ground and flight vehicle test activities. Results are presented of both theoretical and experimental data analysis performed to determine the positioning accuracy attainable from the proposed multistatic acoustic navigation sensor. In particula...

The Journal of the Acoustical Society of America, 2007

An onboard microphone ͑Telemike͒ was developed to examine changes in the basic characteristics of echolocation sounds of small frequency-modulated echolocating bats, Pipistrellus abramus. Using a dual high-speed video camera system, spatiotemporal observations of echolocation characteristics were conducted on bats during a landing flight task in the laboratory. The Telemike allowed us to observe emitted pulses and returning echoes to which the flying bats listened during flight, and the acoustic parameters could be precisely measured without traditional problems such as the directional properties of the recording microphone and the emitted pulse, or traveling loss of the sound in the air. Pulse intensity in bats intending to land exhibited a marked decrease by 30 dB within 2 m of the target wall, and the reduction rate was approximately 6.5 dB per halving of distance. The intensity of echoes returning from the target wall indicated a nearly constant intensity ͑−42.6± 5.5 dB weaker than the pulse emitted in search phase͒ within a target distance of 2 m. These findings provide direct evidence that bats adjust pulse intensity to compensate for changes in echo intensity to maintain a constant intensity of the echo returned from the approaching target at an optimal range.