Unmanned Systems Technology 005 | Selex ES Falco UAV | Sense and avoid systems | RCV Engines DF70 | DSEI show report | Fuel cells | CUAV Expo, InterDrone and CUAV Show reports | SLAM

36 Focus | Sense and avoid systems and different processing algorithms, as well as how to combine the data from the various sensors around the craft. A newer technique is to use the power of processing in the cloud to collate position data transmitted from UAVs, and combine this with other data to create an automated sense and avoid ATC system. So there are various options, which vary with the type of platform. They also vary with the operating conditions, notably under Visual Flight Rules (VFR) or Instrument Flight Rules (IFR). While IFR is easier to address with technical solutions such as radar and transponders, VFR presents the greater challenge of replicating the pilot’s view and improving on the time available to provide a change of course to avoid any risk of a collision. For larger UAV platforms that are often piloted remotely, the challenge over the past few years has been airspace integration – allowing these craft to be used in controlled airspace. Rules of engagement One of the main challenges to overcome is not to replace the human in the cockpit but to give remote pilots the same capabilities an onboard pilot would have. That means having to detect and track aircraft further out to give the pilot more time to talk with ATC, which may mean sensors with higher performance. The problem and the solution are very different depending on the type of operation for the unmanned aircraft. For example, in the US the requirements for a small craft under 25 kg (55 lb) and flying anywhere under 500 ft are very different from one flying at 3000 ft in controlled airspace. Larger manufacturers are focused primarily on the IFR environment, which allows operation in all controlled airspace, particularly at altitudes above 1000 ft. These manufacturers are looking at mature solutions, integrating established technology into the aircraft to solve the problems in the near term. One of the key projects uses Ikhana, a variant of the Predator B UAV, for flight tests as part of the UAS Integration project in the US. It is being used to deliberately trigger on-board collision avoidance (CA) systems and to allow the remote pilot to perform self-separation via specially designed traffic displays. Here the idea is a combination of CA and self-separation or traffic avoidance, so that a craft can remain ‘well clear’ of others and be a good user of the airspace. The aim is ideally never to trigger a CA situation, and one approach is to define what that means for an electronic system. One concept is to keep the remote pilot in the loop as much as possible – there’s not necessarily an algorithm telling the pilot how to manoeuvre, giving them all the information from the UAV on a display on the ground. This is exploring different ways to help the remote pilot understand where the potential collision risks are and to allow them to determine the best solution based on right-of-way rules and the objectives of the mission. To develop statistical data on how these encounters can happen, computer simulations using ATC in ‘human in the loop’ (HIL) systems help developers understand how pilots and controllers interact by testing out different display and ground station concepts. More than 1000 scenarios with various collision courses give the remote pilot the ability to determine how to manoeuvre in response to a potential collision. There are three sensor systems currently being used for prototype sense and avoid on platforms above 60 kg. The TCAS (Traffic Collision Avoidance System) interrogates other aircraft transponders, and over time builds up a picture of where all the other aircraft are, and this works at up to 14-20 miles. ADSB – automatic dependent surveillance broadcast – then provides GPS information about other ADSB-enabled aircraft in an area of 60 miles. Dec 2015/Jan 2016 | Unmanned Systems Technology Pods with small radar systems are being installed on test systems for sense and avoid applications (Courtesy of IMSAR) One challenge to overcome is not to replace the human in the cockpit but to give remote pilots the same capabilities an onboard pilot would have