Unmanned aircraft are a vital asset in today’s world. They have made aerial photography and videography cheaper and more accessible to both hobbyists and small business owners.
Today, the major hurtle is UAS integration into national airspace (NAS). One of the major aspects to integration of UAS into NAS is the ability for systems to sense and avoid other aircraft or obstacles. In the current FAA regulations, the term “see and avoid” exist, but in the future “sense and avoid” will be applied (Carey, 2013). Until that point UASs are unable to comply with the requirements, but this has not stopped companies and the military from working towards smart solutions to the providing a sense and avoid system that are dependable enough to garner FAA approval and support.
The techniques for monitoring separation from both manned and unmanned systems come in multiple forms. The overarching concept, regardless of technique, is that the UAS is informed of nearby traffic and can execute a predictable solution that will provide regulatory separation. The two major techniques to gathering this traffic information can be categorized as ground based or airborne based sensing. Ground based sensing utilize radar systems similar to air traffic control agencies. The major difference is that these radar systems integrate directly into the ground control station (GCS) of the UAS (SRC Inc. 2016). The airborne technique relies on advanced sensors being equipped directly on the air vehicle portion of the UAS. A lot of research is going into the development of micro radar systems that would be able to fit a highly capable radar system into a very small package (Gorwara, 2014).
Some of the major considerations that need to be factored in when deciding between ground based sensing or airborne sensing needs to be attributed to both the size and type of UAS airframe in questions. Small UASs need to be very cognizant of size power and weight of any additional sensors that need to be added to the air vehicle. These systems may benefit from a ground based system that is able to communicate with the ground control station. Additionally, micro radar systems are being produced to provide small quadcopter sized UASs with a robust ability to sense and avoid traffic with light weight and low power solutions (Gorwara, 2014). Large UASs like military grade UASs have a large payload capacity and a large power source capable of both carrying and powering complex sensors that can provide adequate sense and avoid capabilities. Another aspect to consider is the type of airframe in question. A small quadcopter may move slowly and within a relatively small range. This means less powerful sensors could be used to provide the separation and spacing required. Large fast fixed wing system could fly at high altitudes and at high speeds with an enormous range, so providing powerful onboard solutions may make the most sense.
Some larger systems like the MQ-4 global hawk actually have terminal collision and avoidance system (TCAS) which is used on most large commercial manned aircraft. There is also research into a new system call Airborne Collision Avoidance System for Unmanned Aircraft or ACAS Xu for short. This system will integrate with TCAS as well as provide autonomous functions that will support proper sense and avoid decision making if the UAS has lost link or is in autonomous flight (NASA, 2015).
Another current initiative is the use of a system called the ground based sense and avoid system (GBSAA) by SRC Inc. This system is currently being installed by the US Army at posts that are hubs for large UAS training. Fort Hood and Fort Campbell are both test beds for this technology (Mishory, 2016). The system utilizes powerful and expensive ground based radar dishes to directly communicate any traffic advisories directly to the GCS of the UASs operating within its area of responsibility. This system can detect both manned and unmanned aircraft as well as other airborne obstacles. The benefits of this system are that just one GBSAA can provide coverage for multiple aircraft working in a defined area. Also, GBSAA does not add any additional power or weight requirements to the actual air vehicles that are utilizing its information (SRC Inc., 2016).
Regardless to size and type, the need for FAA approved sense and avoid systems is vital to the integration of UAS into NAS. By understanding the limitations and capabilities associated with the size and type of a UAS will help engineers provide the best solution to each system on a case by case basis. The need to ensure the right capability is equipped on the right system is also vital in reducing excess costs and ensuring the general UAS user base is capable and willing to equip their UASs with these systems when it becomes available. Additionally, integrating the UAS sense and avoid technology into manned sense and avoid systems like TCAS will be vital to future integration.
References
Carey, B. (2013, June 22). FAA Plans Unmanned 'Sense and Avoid' Rule in 2016. Retrieved
October 03, 2016, from http://www.ainonline.com/aviation-news/air-transport/2013-07-22/faa-plans-unmanned-sense-and-avoid-rule-2016
Gorwara, A. (2014). Doppler micro sense and avoid radar. Retrieved October 3, 2016, from http://pmi-rf.com/documents/DopplerMicroSenseandAvoidRadarPaper.pdf
Mishory, J. (2016, June 16). Initial UAS flights using GBSAA system at Ft. Hood have been delayed. Retrieved October 03, 2016, from https://insidedefense.com/daily-news/initial-uas-flights-using-gbsaa-system-ft-hood-have-been-delayed
NASA. (2015, January 25). NASA, FAA, Industry Conduct Initial Sense-and-Avoid Test. Retrieved October 03, 2016, from http://www.nasa.gov/centers/armstrong/Features/acas_xu_paves_the_way.html
SRC Inc. (2016). Ground-Based Sense and Avoid Radar System. Retrieved October 03, 2016, from http://www.srcinc.com/what-we-do/radar-and-sensors/gbsaa-radar-system.html
No comments:
Post a Comment