Unmanned Maritime Systems for Search and Rescue

Eli Hini
Eli Hini
Jun 11, 2018 · 6 min read

A short exposè on the use of REMUS 6000 emergency response

Introduction

Unmanned Maritime Vehicles (UMVs) can be divided into two categories; Unmanned Surface Vehicles (USVs) and Unmanned Underwater Vehicles (UUVs) have been deployed in a number of search and rescue (SAR) and as well as recovery efforts since 2005. The deployment of AEOS-1 to map the seawall and to assist with repairs in 2005 following the aftermath of Hurricane Wilmar spelled a notable milestone for the use of USVs in disaster relief efforts (Murphy et. al., 2008). AEOS-1 which was originally designed as an environmental monitoring was equipped with acoustic image sensors which allowed it to provide below-the-surface images and scans to emergency workers.

Acoustic sensors and computational technologies have since improved. Newer vessels have been designed and developed specifically for SAR missions and the Hydroid REMUS 6000 (Hydroid, n.d) is one of such vessel that has been deployed recently for underwater emergency response . The remainder of this article describes briefly the REMUS, recent successful missions, its sensor suite, modification to the sensor suite if any and a recommendation for use in cooperative unmanned systems SAR operations.

REMUS 6000

Hydroid’s REMUS 6000 is a UUV designed to operate as a submersible capable of autonomous operation at 6000 meters below the surface. It is a class of UUVs that are known as Autonomous Underwater Vehicle (AUV) because they can operate automatically with direct control from a pilot. REMUS 6000 can operate without interruption for up to 22 hours and with its field replaceable batteries, it can perform its operation continuously without meaningful delays.

Use in SARs mission

The REMUS 6000 was deployed in the search for the missing Air France Flight 447 passenger airliner which crashed into the Atlantic Ocean on June 1, 2009 (ASDNews, 2017). In August 19 of 2017, the REMUS 6000 was used in the discovery of the U.S. Navy heavy cruiser. The Indiana, which sank in 1945 in the Philippine Sea 5,500 meters below the surface.

Sensor Suite

Designed for maritime environment REMUS 6000 is equipped a number of acoustic-based sensors and transceivers to aid in underwater navigation, sensing and imaging such as the following:

1. Acoustic Doppler Current Profiler

2. Side-scan Sonar

3. Depth Sensor

4. Conductivity Sensor

5. Temperature Sensor

6. Multi-Beam Echo Sounder

7. Sub-Bottom Profiler.

Using the principle of Doppler Effect, the Acoustic Doppler Current Profiler (ADCP) is a exteroceptive sensor used in measuring the speed and direction of ocean currents (Ocean Explorer, n.d). An ADCP has 4 acoustic transducers that emit and receive acoustical pulses. Using Doppler Effect, this sensor emits a sequence of high frequency acoustical pulses which reflect off moving particles in the water. The time delay, frequency, pitch and the direction of travel of echoed signals are used in determining the speed of current.

A Side-scan Sonar is used imaging the seafloor. This external sensor is especially efficient and important where visible light imagery may not produce a clear image without being illuminated. Side-scan sonars work by emitting conical or beamed acoustical pulses towards the seafloor or a submerged (or wrecked) body and the amplitude of the echoed signals are stitched together to form an image (Buscombe et. al., 2016).

The Depth sensor is used in measuring the depth of the vertical distance (depth) of the UUV from the surface of the water. It uses the pressure exerted by the surrounding water as the UUV travels vertically down. The further the UUV is from the surface, the higher the water pressure and density (Mohd et. al., 2012). This sensor important because it not only signals to the UUV about its relative or absolute depth but also its safe operating depth. This sensor coupled with an inertial navigation system, a proprioceptive sensory system, is used in determining current location and distance travelled through the use of dead reckoning.

Conductivity sensors measure electric conductivity or resistance of the water. The higher the salinity of the water, the more conductive it will be. The temperature sensor is used in measuring the temperature of the surrounding waters. An internal temperature sensor is used in monitoring the overall hull and component temperature.

The Multi-beam echo sounder works by uses beamforming and the same principle as the Side-scanner sonar to create high resolution and precise imaging. It is made up of an array of acoustic transducers used in imaging the ocean floor or surrounding object. The acoustic beams are controllable and can be manipulated depending on the surrounding and speed of the vessel to provides higher resolution imagery than a Side-scan sonar (Wang et. al., 2014). It also provides other information such as heave, pitch, roll and yaw.

Using a Sub-bottom profiler, the UUV can examine and gather information on various sediments on the ocean floor, wreckages and other objects such as pipelines, undersea cables and structures. It is also an acoustic-based instrument that emits acoustical pulses which penetrate sediments to gather data (Griffin, Kuhn & Kim., 2005).

Given that radio communication is not ideal under water, UUVs communicate their data and location with each other and their command stations using a distributed acoustic communication transceivers (Sullivan, 2017). For REMUS 6000, it communicates with the ground communication station, which is usually a ship, using the acoustic transponders and modems installed on the bottom of the ship. The AOV itself is also outfitted with GPS, WiFi and Iridium Satellite communication package to be used to communicate with the ground when it surfaces. It can upload data and current location through satellite communication when the command ship is not nearby with WiFi communication reserved for high bandwidth to communication with nearby command and control ships.

Cooperative unmanned maritime systems and unmanned aerial systems

Unmanned aerial vehicles (UASs) can complement UMSs and increase the efficiency of emergency response operations in many ways. An unmanned aerial vehicle (UAV) can be used to act as wireless access point that connects surfaced AOVs or USVs to command stations or to other unmanned vehicles in the area thereby forming a cooperative network(Murphy et. al., 2008; Reese, 2015). Furthermore, UASs can provide aerial imagery to guide USVs and UMVs as they traverse a wreckage or disaster area. Using object recognition algorithms images from a UAS can be used in identifying victims from above in real-time and this information can be relayed to the UMVs as to where to go.

Advantages of UMS over their manned counterparts

The advantage of a UMS, just like most unmanned system is the cost per deployment is much lower as the system design doesn’t need to account for sustaining and protecting onboard human crew. This allows the design to be streamlined for the intended operational environments. There many cost reduction in life support sensors and the overall vehicle can be considered one massive suite of sensors depending on the its mission.

References

Buscombe, D., Smith, S. M. C., & Grams, P. E. (2016). Automated riverbed sediment classification using low-cost sidescan sonar. Journal of Hydraulic Engineering, 142(2), 6015019. doi:10.1061/(ASCE)HY.1943–7900.0001079

Griffin, S. R., Kuhn, S. C., & Kim, B. (2005). Parametric sub-bottom profiler for AUVs. Sea Technology, 46(7), 31–32,34–35. Retrieved from http://search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/198582276?accountid=27203

Hydroid (n.d). REMUS 6000. Retrieved from https://www.hydroid.com/sites/default/files/product_pages/REMUS_6000_Brochure_2017_0.pdf

Mohd Shahrieel Mohd Aras, Abdullah, S. S., Shafei, S. S., Mohd Zamzuri Ab Rashid, & Jamali, A. (2012). Investigation and evaluation of low cost depth sensor system using pressure sensor for unmanned underwater vehicle. Majlesi Journal of Electrical Engineering, 6(2), 21.

Murphy, R. R., Steimle, E., Griffin, C., Cullins, C., Hall, M., & Pratt, K. (2008). Cooperative use of unmanned sea surface and micro aerial vehicles at hurricane wilma. Journal of Field Robotics, 25(3), 164–180. doi:10.1002/rob.20235

Ocean Explorer (n.d). Acoustic Doppler Current Profiler. Retrieved from https://oceanexplorer.noaa.gov/technology/tools/acoust_doppler/acoust_doppler.html

Reese, M. (2015). ICARUS unmanned maritime search and rescue system demonstrated in Portugal. Retrieved fromhttp://www.unmannedsystemstechnology.com/2015/07/icarus-unmanned-maritime-search-and-rescue-system-demonstrated-in-portugal/

Sullivan, J. (2017). An acoustic positioning buoy. IEEE Potentials, 36(2), 16–19. doi:10.1109/MPOT.2016.2630378

Wang, Y., Wang, S., Shao, S., Wu, Z., Zhang, H., & Hu, X. (2014). Measurement error analysis of multibeam echosounder system mounted on the deep-sea autonomous underwater vehicle. Ocean Engineering, 91, 111–121. doi:10.1016/j.oceaneng.2014.09.002

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