Unmanned Systems Technology 008 | Alti Transition UAS | Ground control systems | Xponential 2016 report | Insitu Orbital N20 | UAVs | Solar power | Oceanology International 2016 report

34 Focus | Ground control systems the craft, while the second screen can display the data from the payload, usually still and video imagery. Unlike a small UAV mission though, these GCSs need to be set up quickly, and the operators sit at them for many hours, so a larger screen size has to be supported. The requirement for these screens is not necessarily high resolution but high brightness, especially if operating outdoors, so the two screens need a brightness of 1500 nits (the common measure of brightness equivalent to 1 candela/m 2 ) compared with a consumer monitor at 500 nits. There is another issue in that the monitors have to be able to operate down to -20 C, and most commercial screens cannot do this. The single-screen version implements a ‘picture-in-picture’ to combine the two. It is seen as more portable, being battery powered, while the dual and triple screens are used for system development or missions of more than an hour, so have a more static control centre often powered by a generator. Many GCS designs for smaller unmanned systems are based around a commercial ruggedised laptop running the Windows operating system, with custom power subsystems and interface cards. This provides the latest microprocessor technology such as the Intel Core i5 processors in a casing that is dust-, water- and vibration-proof to the IP65 standard, and drop-proof from a height of up to 180 cm. The systems are designed to operate in temperatures ranging from -20 C to +60 C so that they can be used anywhere from the desert to the poles, but this requires the use of components such as high-temperature electrolytic capacitors on the motherboard that are not necessarily used on commercial boards. This though allows the fully ruggedised models to comply with the MIL-STD 810G military standard for reliability. Using a commercial PC platform allows the GCS provider to easily upgrade the performance of the system and simplifies the addition of peripheral boards. These can all be added via the USB ports and controlled with existing C libraries, making the software development simpler than with a fully custom design. With 2.4 GHz processors, the platform’s response time of 30 ms is sufficient to provide the control to the unmanned craft, as this is largely about setting waypoints for the navigation system and autopilot on the craft. This comes from using a mature operating system such as Windows 7 and the software development skills to ensure that unnecessary operations do not interfere with the critical control paths, and is one reason for the transition to the latest operating system, Windows 10, being slower than on the desktop PC. Power Keeping the GCS powered depends on the way the system is configured. For long missions, operators and data analysts are seated at the terminal and use power from a generator; with shorter missions, with a man-portable GCS, multiple standard battery packs are used. These are connected to a ‘hot- swappable’ interface board that allows one battery to be removed and replaced with a fresh one without interrupting the operation of the mission. Two battery packs can provide six to seven hours of power, enough for most flights. However, operations in remote areas may not be within range of a cellular network, so the ground station may store the data locally for analysis later. The GCS in this scenario will struggle to link back to the cloud, so additional wireless connectivity such as a satellite link may be needed, and June/July 2016 | Unmanned Systems Technology The assembly of a single screen GCS (Courtesy of Flying Production) Using split-screen display software allows a single-screen GCS to display data from a range of sources (Courtesy of UAS Europe)