ADS-B Detect, Sense and Avoid Sensor Selection for Unmanned Aerospace Systems

Introduction

There is a need for a more efficient and safer environment in support of existing aeronautical operations that reduce the risk of collisions for manned and unmanned aircraft.  Operators of Small Unmanned Aerospace Systems (sUAS) under 55 pounds hold a responsibility to safe flight in the airspace in which they are permitted.  Payload weight on aircraft this small is significant and should be kept to a minimum for operating efficiency.  Weight requirement and cost effectiveness are key factors for Sense and Avoid (SAA) sensor selection.  A Traffic Collision and Avoidance System (TCAS) are too large and heavy for sUAS.  SAA technology for UAS is part of a much bigger picture. 

Each development brings UAS closer to their consent in the National Airspace System (NAS).  NASA conducts collaborative research “with the Federal Aviation Administration (FAA), the Radio Technical Commission for Aeronautics (RTCA) and commercial aerospace entities to develop minimal operation performance standards (Behar, 2017).”  For UASs, detecting is to determine there is an object in the airspace but not to assume the object has been identified.  Sensing is to determine that the object is or is not a threat to a UAS.  Avoidance is to initiate movement from the flight path to a new heading and back to the original course.  This paper discusses the application of Automatic Dependence Surveillance Broadcast (ADS-B): a technique that is ideal for SAA application on a sUAS.

ADS-B Application

            SAA capability is a key enabler for UAS to safely have access to all ranges of airspace.  The approach to automatic detection should be a unified method for air-based and ground-based SAA.  For manned aircraft TCAS and ADS-B is a cooperative sensor solution and warn aircrew of air traffic.  Due to constraints for size and weight, TCAS cannot be applied directly to sass and has demonstrated it is not ideal for use at airports and other dense airspace conditions (Zhao, 2016). 

A long term solution for SAA is real-time ADS-B data.  While still in its experimental form, algorithms designed with ADS-B data for sUAS can generate capability to effectively sense and avoid intruders.  “ADS-B can obtain the position, speed, course and other information of the host aircraft via the integrated Global Position System (GPS) and send it out in the form of broadcast, while the aircraft or ground control station can receive the precise location data broadcast information which equipped with the same ADS-B (Zhao, 2016).” 

Figure 1: ADS-B Architecture (Zhao, 2016)

ADS-B satellite traffic management is effective, economical and will optimize the cohesion of UAS and manned aircraft.  ADS-B technology is a satellite air traffic control (ATC) system and will eventually phase out ATC radar.  Not only is the cost of an ADS-B ground station is one-ninth of the conventional ATC secondary radar, its data monitor updates faster at every second (Zhao, 2016).  ADS-B is also used for ground movement and helps prevent runway incursion.  GPS sensors support a 2-way system function.  “ADS-B OUT transmits aircraft flight number, address code, heading, speed, vertical speed,(Zhao, 2016)” and other information such as weather and route reflection.  ADS-B IN receives ADS-B OUT data that other aircraft have broadcasted.  The architecture is shown in figure 1.  The sUAS onboard processer is provided real-time information of the airspace environment, increases situational awareness and can make assessment of in

Conclusions

ADS-B is a low-cost light-weight solution for SAA for UASs in airspace.  This factor is necessary to meet sUAS requirements for weight and cost using onboard GPS.  The same requirements for avoiding potential collisions and other hazards exist for autonomous and remotely piloted aircraft (RPA).  ADS-B is not an obstacle avoidance system, but will prove to be a tool moving forward for the integration of UAS in all airspace.

References

Behar, M. (2017). Drones in a Busy Sky. Air & Space Magazine. Retrieved 8 May 2017, from http://www.airspacemag.com/flight-today/drone-tests-180960069/

Baraldi Sesso, D., Vismari, L. F., Vieira da Silva Neto, Antonio, Cugnasca, P. S., & Camargo Jr, J. B. (2016). An approach to assess the safety of ADS-B-based unmanned aerial systems: Data integrity as a safety issue. Journal of Intelligent & Robotic Systems, 84(1), 621-638. doi:10.1007/s10846-015-0321-0

Zhao, C., Gu, J., Hu, J., Lyu, Y., & Wang, D. (2016). Research on cooperative sense and avoid approaches based on ADS-B for unmanned aerial vehicle. Paper presented at the 1541-1546. doi:10.1109/CGNCC.2016.7829019