UAS Sensor Placement

The field of unmanned aviation has expanded rapidly over the last two decades. Small unmanned aerial systems (sUAS) are the largest segment of unmanned aviation, and arguably unmanned systems in general, and their exponential growth has contributed to a blossoming hobbyist and commercial market. With so many choices on platforms, where does a new unmanned pilot start when searching for a suitable aircraft. There are certainly many uses for sUAS, so addressing all wouldn’t be feasible with a single paper. This work will focus on two of the most common uses for sUAS and offer suggestions for viable platforms.

The first use examined will be from the commercial side of unmanned aviation. From the onset of unmanned system use in aviation unmanned aerial systems (UAS) have been used in large part for remote imagery platforms. UAS have served the military well as intelligence, surveillance, and reconnaissance (ISR) platforms, so it’s no surprise operators saw value in aerial imagery collection for commercial use. Aerial photography/videography is a very popular use for commercial sUAS operators. There is a litany of unmanned systems commercially available, many of which are capable aerial camera platforms, making selecting platform a challenge.

A proven industry leader in sUAS is DJI. The firm produces high quality aerial photography drones. The Phantom 4 Pro (see Figure 1) is one of their commercially available platforms that strikes a good balance of aerial film making ability and modest price. The sUAS is a satellite navigation equipped quadrotor multi-copter capable of a high level of autonomous function (Phantom 4 Pro, 2017). The aircraft has an integrated 5-direction obstacle sensing system and is designed for 4-direction obstacle avoidance (Phantom 4 Pro, 2017). The key feature of the system, however, is the camera. The three-axis, gimbal mounted camera utilizes a 1-inch 20-megapixel complementary metal oxide semiconductor (CMOS) sensor and is capable of filming in 4K resolution at a rate of 60 frames per second as well as taking still photographs at 20-megapixels (Phantom 4 Pro, 2017). DJI’s positioning of the camera below the body allows for unrestricted view of the subject and the gimbal allows to camera to shoot smooth and stable photos and video.

Figure 1. DJI Phantom 4 Pro image as http://store.dji.com/product/phantom-4-pro?site=brandsite

The impressive gimbal stabilized camera system of the drone is what makes it an ideal choice for commercial aerial photography and film making. Airworthiness, ease of operation, and relatively low acquisition cost all serve to solidify this choice. At a suggested retail price of $1499, the system is a reasonably priced and capable commercial sUAS (Phantom 4 Pro, 2017).

The next use examined is from the hobbyist side. Hobbyist unmanned aviation is more established than its commercial counterpart. The hobby stems from remote controlled aircraft of various types. A rapidly growing segment, however, is drone racing. With several classes and ability levels, selecting a suitable platform can also be difficult. Systems are very customizable and can be adjusted to suit the operators liking. Racing drones are small in comparison to most aerial photography sUAS and are purpose built to be fast and agile. Racers fly their multi-copter through a course of obstacles utilizing first-person view (FPV). Classes are based mainly on the size of battery cell used to power the aircraft, 250mW being the most common and a great place to start.

A lead hobby sUAS producer, Walkera, offers drone racing kits for every class of competition. Walkera offers several 250 class options with the Runner 250 PRO (see Figure 2) topping the list in ability. The quadrotor platform features a lightweight 464g aircraft (battery excluded) with a 143mm rotor diameter (Runner 250 Pro, 2017). The system uses quality electronic components and brushless motors. The integrated camera on the aircraft is high definition, 800 Television Lines (TVL) resolution sensor, optimized to transmit video at 5.8GHz (Runner 250 Pro, 2017). The forward and centerline placement of the camera allows for an unobstructed first-person view from the platform. The adjustable tilt allows for compensation for nose low attitudes required for high speed flight.

Figure 2. Walker Runner 250 PRO image as http://www.walkera.com/index.php/Goods/info/id/43.html

Light weight, solid build, good components, and a camera system designed for FPV use contribute to making the Runner 250 PRO a very viable FPV racing drone.

Both the sUAS mentioned are prime examples of how unmanned system designers tailor build these aircraft for their intended use. DJI designs drones to be employed as aerial cameras, while Walkera is focusing on the very unique need of hobbyist FPV racers. The applications for drones continue to grow, and the commercial drone market will most assuredly follow that trend.

References

Phantom 4 Pro. (2017). DJI. Retrieved from https://www.dji.com/phantom-4-pro

Runner 250 Pro. (2017). Walkera. Retrieved from http://www.walkera.com/index.php/Goods/info/id/43.html

Figure

Artemis: The Hunt for MH370

Unmanned Systems Maritime Search and Rescue    

On 8 March 2014, a Boeing 777-200ER commercial airliner operated by Malaysia Airlines lost contact with air traffic control and disappeared from radar tracking systems. The regularly scheduled international flight (MH370) originating from Kuala Lumpur, and bound for Beijing, failed to reach its destination. The loss of all 227 passengers and 12 crew members prompted what has been the largest, and most expensive, multi-national search effort in aviation history (Pearlman, 2014). On 21 March 2014, the U. S. Navy dispatched Phoenix International Holdings, Inc. (Phoenix) to conduct undersea search services as part of a Naval Sea Systems Command (NAVSEA) support contract (LeHardy & Moore, 2014). Phoenix deployed a Bluefin 21 autonomous underwater vehicle (AUV) as part of the effort to locate the submerged wreckage (LeHardy & Moore, 2014). While the aircraft’s data recorders have not been located, the employment of the AUV did lead to successful collection of data at extreme depths. This paper will examine the platform used by Phoenix and respond to questions posed in Module 2.4 as they relate to the system.

Figure 1. Phoenix International’s ‘Artemis’ Bluefin-21 Autonomous Underwater Vehicle (AUV) image as published on http://www.phnx-international.com/phnx/phoenix-equipment/auv/

Bluefin Robotics, now a General Dynamics subsidiary, developed the Bluefin-21 (see Figure 1) as a modular platform capable of employing multiple sensors and payloads designed to function underwater autonomously. The range of applications include offshore survey, archaeology & exploration, oceanography, mine countermeasures (MCM), unexploded ordnance (UXO), and as demonstrated by Phoenix, search & salvage (Bluefin-21, 2017). The system specifications of the Phoenix operated Bluefin-21, affectionately known as ‘Artemis’, are listed in Table 1.

Table 1

Artemis AUV Specifications

AUV
Max Operating Depth	5,000 meters
Diameter	21 inches / 0.53 meters
Length	17.7 feet / 5.38 meters
In-Air Weight	1,764 pounds / 800 kg (approximate)
Speed	2 to 4 knots
Estimated Endurance	~20 hours, @ 3 knots
Manufacturer	Bluefin Robotics Corporation
AUV Subsystems
Navigation
Inertial Navigation System	Kearfott Custom KN-6053
ADCP/Doppler Velocity Log	Teledyne RDI Workhorse Navigator 300kHz
Ring Laser Gyro	Kearfott T24 Monolithic RLG
Acoustic Positioning System	Lodestar Gyro USBL [8084]
Depth Sensor	Paroscientific 8CB7000-I
GPS	Thales/ Ashtech DG14
Sound Velocity Sensor	Valeport Mini SVS
Backseat Control Architecture	Bluefin Robotics
Communications
Acoustic Modem	Sonardyne AvTrak 6 [8220]
RDF Beacon	Bluefin - RDF
RF Serial Link	Freewave FGRMT
Iridium Satellite Modem	NAL 9601-D-1
Ethernet Direct	Cirexx CPU1232 Ethernet
Acoustic Payload
Multibeam Echosounder	Reson 7125 (400 kHz)
Side Scan Sonar	EdgeTech 2200-M (120 / 410 kHz)
Sub-bottom Profiler	EdgeTech DW2-16 (2-16 kHz)
Optical Payload
Camera	Proscilica GX1920
Sensor	Sony ICX674
Resolution	1936 x 1456 pixels
Geophysical Payload
Magnetometer	Honeywell HMR2300 3-axis magneto-resistive
Self Potential Sensor	Ultra Electronics (Ag-AgCl)
CTD	AML Oceanographic SmartX
Multibeam Echosounder	Reson 7125 (bathymetry & backscatter)

Note. Artemis specifications as published by Phoenix International Holdings, Inc. (Artemis Specifications, 2016)

Phoenix’s efforts to conduct autonomous search for the wreckage of MH370 with Artemis began after a suspected acoustic beacon signal was traced with towed pinger locators (TPL) to an area of interest in the Indian Ocean. The AUV was programmed to conduct seafloor survey with side scan sonar at the maximum designed operating depth (LeHardy & Moore, 2014). Autonomous search operations were conducted with the system for 70 days covering an area of 860 square kilometers (LeHardy & Moore, 2014). The aircraft was not located, however the high-resolution data collected by Artemis allowed analysts to conclude the wreckage was not located in the search area with a high level of confidence. A wide scale subsurface search of such a large area would have proven much more difficult and costly without the assistance of the Bluefin-21 AUV.

What proprioceptive and exteroceptive sensors does the system have that are specifically designed for the maritime environment?

The Bluefin-21 is designed to operate underwater autonomously, and therefore has many sensors that contribute to its ability to function in the maritime environment. It shares many sensors commonly found on unmanned systems designed to operate in various environments. The proprioceptive subsystems that contributes most directly to subsurface marine operation are the inertial navigation system, the acoustic position system, the depth sensor, and the sound velocity sensors. All of the systems contribute data necessary to navigate in an environment with restricted radio frequency transmissivity. The exteroceptive subsystems that enable the platform to scan below the surface so effectively are the multi-beam sonar, side scan sonar, and sub-bottom profiler. Without those, searching and mapping at the depth the vehicle is designed to operate, would not be feasible.

What is one modification that could be made to the existing system to make it more successful at search and rescue operations?

Phoenix was able to employ the vehicle at its maximum designed operating depth for extended duration missions. During the time of operation, software changes were made to allow for operators to monitor battery status (LeHardy & Moore, 2014). Though a minor adjustment, the change contributed to a significant increase over the originally designed operating endurance; from 20 hours originally, to a record 27 hours and 9 minutes (LeHardy & Moore, 2014).

There is an implied urgency with the mission of search and rescue. With that in mind, any modification to the system that would improve the speed of search could directly contribute to a higher potential for rescue. If a change is made to the sensor payload, any improved sonar capability that increases the sweep width could, in turn, reduce the number of passes required to search an area.

How can maritime unmanned systems be used in conjunction with unmanned aerial systems (UAS) to enhance their effectiveness?

For larger volumes of data, radio frequency (RF) transmission is a well established method. RF transmission in the maritime environment can be challenging for over the horizon communications from surface to surface at greater distances. Unmanned aerial systems could easily act as an airborne repeater to relay data over greater distance. This would most likely require the AUV to surface to do so, however.

What advantages do unmanned systems have over their manned counterparts? Are there sensor suites that are more effective on unmanned systems?

The most significant advantage AUVs have over manned submersibles is operating depth. An unmanned system can more easily be designed to operate at extreme depths because life support subsystems are not required. Additionally, manning a submersible vehicle is less beneficial. For search operations, a submersible is largely reliant on non-visual sensors like sonar. For those reasons, one could argue that it is far less advantageous to use manned submersibles as a sensor platform if unmanned options are available.

References

Artemis Specifications. (2016). Phoenix International Holdings, Inc. Retrieved fromhttp://www.phnx-international.com/phnx/phoenix-equipment/specifications/artemis-specifications/

Bluefin-21 Autonomous Underwater Vehicle (AUV). (2017). General Dynamics Mission Systems. Retrieved from https://gdmissionsystems.com/bluefinrobotics/vehicles-batteries-and-services/bluefin-21

LeHardy, P. K., & Moore, C. (2014). Deep Ocean Search for Malaysia Airlines Flight 370. Paper presented at the 1-4. doi:10.1109/OCEANS.2014.7003292

Pearlman, J. (2014, May 29). SMH370 Search Becomes Most Expensive Aviation Hunt in History, Yet Still No Clues. The Telegraph. Retrieved from http://www.telegraph.co.uk/news/worldnews/asia/malaysia/10863605/MH370-search-becomes-most-expensive-aviation-hunt-in-history-yet-still-no-clues.html