DURIP Time-synchronized vector sensor data acquisition modules for autonomous platforms
Abstract
Acoustic vector sensors have the capability of measuring both the pressure and particle velocity of an underwater acoustic field, which permits them to measure the directionality and other spatial characteristics of a sound field from a single point. Over the past two decades a new generation of acoustic vector sensors have become available with higher bandwidths and smaller volumes. The ability to measure low-frequency sound directionality from a compact and low-power package makes them appealing candidates for deployment from autonomous platforms. Two Office of Naval Research Task Force Ocean grants currently incorporate these sensors into both autonomous deep-drifting (grant number N00014-21-1-2953; PI Aaron Thode) and Wave Glider platforms (grants number N00014-21-1-2791 & N00014-21-1-2558; PIs Luc Lenain and Karim Sabra). Both projects are currently using off-the-shelf data acquisition systems (DAQ) that consume high amounts of power and are not optimized for reading the simultaneous analog and digital data generated by these sensors. The DAQ systems are also vulnerable to clock drift, so no time-synchronized data is available for coherent passive acoustic signal processing between platforms deployed simultaneously. Under a previous DURIP award (N00014-23-1-2235) the Keyport Naval Undersea Warfare Center (NUWC-KPT) built 12 autonomous vector sensor data acquisition modules (VS-DAQM) in collaboration with the Scripps Institution of Oceanography (SIO) at the University of California San Diego (UCSD). These modules have been designed with a rechargeable lithium-ion battery system inside a pressure case with a custom-designed cage mounted on one endcap, that limits both mechanical vibration and flow noise contamination on a VS-209 vector sensor. The battery pack permits at least 72 hours of continuous recording from the sensor, and up to two weeks under a duty cycle or with external power supplied.Under this DURIP four additional VS-DAQM systems will be built, and additional software features will be added to the resulting 16 hardware platforms. First, an external time synchronization feature will be added that will permit two separated VS-DAQM systems to be time-synchronized despite being deployed on different platforms. Second, a hibernation/wake-up feature will be added to allow the timing of initial recording to be adjusted. Third, an expanded serial command suite and improved Graphic User Interface (GUI) will be written to allow modifications to the data sampling rate, non-acoustic orientation data polling rates, internal clock time, and sensor calibration coefficients. Finally, a full calibration of acoustic and non-acoustic sensor data streams will be conducted, and the resulting calibration coefficients stored in the VS-DAQM memory to permit fully-calibrated data to be recorded and stored immediately.An additional optional budget requests support to design and build a six-month duration autonomous bottom-mounted version of the VS-DAQM, by building a larger battery case and using revised deployment hardware.Existing commercial and previous DURIP-funded data acquisition systems cannot sampleboth analog and digital data, and do not allow external synchronization signals. Furthermore, there are strategic long-term advantages in permitting university oceanographic institutions to collaborate with a Navy lab that has practical experience working with these sensors. These advantages include an ability to easily customize and upgrade the DAQ software and memory capacity based on evolving sensor designs and applications, a flexibility not offered by commercial systems. The equipment has numerous additional future applications for other bottom-mounted and mobile platform applications, including an ongoing DARPA program for monitoring fish andcrustacean settlement on artificial reef structures.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 09, 2024
- Source ID
- N000142412777
Entities
People
- Aaron Thode
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego