The USAF Research Laboratories have launched an advanced technology demonstration programme to test the feasibility of fitting an optical sense and avoid system aboard the US Army's AAI RQ-7B Shadow 200B tactical UAVs.
The small sense and avoid system (also known as SSAASY) advanced technology demonstration programme is based on miniaturising sensors initially developed by Defence Research Associates and AFRL for the General Atomics MQ-1 Predator and Northrop Grumman RQ-4 Global Hawk.
The programme was launched in March with funding until the end of 2009 coming from the Office of the Secretary of Defence's technology transition initiative.
AFRL proposes fitting Shadow with three fixed optical sensors with these having overlapping fields of regard. Each individual sensor will monitor and arc covering +-110 degree in the horizontal and +-15 degree in elevation. Software algorithms monitor the optical field on a constant basis seeking objects moving relative to the background motion of the sky.
"If there is a hole in the flow field, that indicates that there is something there that is potentially on a collision course with you," says AFRL sensors directorate researcher John McCalmont.
"We track and analyse it and potentially pass it on as a threat to the observer or the autopilot."
Speaking at the Unmanned Vehicle Systems International UAV 2007 conference in Paris last month, McCalmont said that the basic concept of operation being proposed would see the UAV pilot or operator being responsible for initiating an avoidance manoeuvre consistent with existing rules of the air.
"We want that Shadow can see any aircraft that can pose a potential threat to them. We want to generate those threats on board the aircraft and then pass that information down to the ground pilot with a recommended manoeuvre.
"Right now the concepts of operations are that the pilot will do the execution of that avoidance manoeuvre. In other words he will be actively involved in the loop to do the manoeuvring, however as the autonomous systems come on board that may change. We have seen this many times where initially the operators want manned control over all or most of the aircraft, but eventually they see the advantages of autonomous manoeuvring and they eventually shift to that kind of operation. But as of now we have a human in the loop for the avoidance manoeuvre."
The system will incorporate a 500ft (150m) minimum miss separation in its manoeuvre model, but will aim to provide a layered series of warnings to the operator. "Right now we are in the process of solving this geometry specifically for the Shadow UAV."
The initial trial sensor suite is expected to have an all-up weight of 4.5kg (10lb) and draw 160w of power. The final phase system is anticipated to have total weight of no more than 0.5kg and draw just 30w of power so as to avoid any significant changes to the Shadow design. "We want to minimise any modifications that we have to do to that aircraft or change its operating characteristics."
The programme is currently in the final stages of its requirement definition phase. This has included development of a simulation model of how Shadow would integrate into the US national airspace and the type of aircraft it is most likely to encounter in any collision scenario.
A 24-month design and build phase will be launched late this year. This will include laboratory testing and initial flight trials aboard a surrogate aircraft operated by the Physical Sciences Laboratory at the New Mexico State University.
The final phase is targeting detailed test and valuation of the mature lightweight version aboard a Shadow 200B during December 2009, with those flights planned for the White Sands missile range.
AFRL hopes that the trials will also demonstrate whether the same sense and avoid capability can be ported to other small UAVs: "We want to determine the feasibility of this technology can we put it on a variety of small unmanned air systems, not just Shadow?"
The existing DRA optical sensor suite is currently undergoing integration with TCAS under a separate USAF small business innovative research effort launched in 2004 to support full-scale development of the system for carriage aboard Predator and Global Hawk.
A proof-of concept demonstration of that variant was conducted in January 2005 with work now focusing on development of operator interfaces to allow meaningful interpretation of warning and alarm data.
Source: Flight International
