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

36 this requires additional power. That then drives the demand for a truck with a back-up generator. Control One issue faced by GCS designers is the need to simplify the user interface for controlling the craft. An implementation with two joysticks is common, each with three-axis control with up to 36 switches that can be used as a remote control for the craft and the camera system. The function of these switches can be modified through the Windows USB interface to map onto specific autopilot functions such as rudder, aileron and thrust control; the more switches available the finer the control can be. Some GCSs also provide switches that can be customised for functions such as triggering a UAV parachute at the end of a mission. All of this is easily handled within the Windows environment. The control of the gimbal for the camera uses a serial connection from the autopilot. In this scenario the data links have a couple of pass-throughs, so one serial connection is used for the autopilot and telemetry, and the other to control the gimbal by moving it with the joystick. This shows how important it is to have all the external interfaces available – the LAN/Ethernet port, serial lines, external power, USB ports to download maps or videos, and the HDMI port to deliver video to a big screen or on to a command and control centre. Communications The comms with a UAV is another area where the base GCS is modified. These connections can be standard 2.4 GHz links or use other frequencies chosen by the UAV supplier or the customer. The comms boards are mounted inside the GCS, with a heat sink and wiring to connect the antenna, plus a digital switch between external directional and omnidirectional antennae. GCS manufacturers will leave an empty space inside the box for the end- user to install their own data links so that the same generic system can be used with UAVs, ground robots for mine clearance or other surface vehicles that run via fibre optic control, for example. All the changes are handled in the software, saving cost and integration time. For long-range UAV systems that travel beyond the line of sight, using an external antenna that can be moved to follow the craft in the air allows different comms protocols and frequencies to be used by just changing the interface board. Simpler systems with an internal or fixed antenna are restricted to a certain set of frequencies, and this often then also determines which protocols can be used. For example, wi-fi or Bluetooth only operate at 2.4 GHz, while other links have a longer range with the 868 MHz or 915 MHz bands, but these require larger antennae and carry less data. Directional antennae can be used with other frequencies such as S band at 2.1-2.3 GHz and go up to C band at 4-5 GHz. The choice of frequency and protocol comes down to the customer’s requirements, and requires the GCS developer to modify the antenna. As a result, a flexible ground station needs to be able to support this range of antennae and radio protocol boards via the PC port. It also means having different voltages – 5, 12, 24 and 28 V – to power the antennae and the boards, and provide flexibility for the operator. Adding the antenna system with a mast-based, pan-and-tilt dish antenna brings some other subtleties. Placing the RF linear power amplifiers on the antenna side means the coax cables from the dish are as short as June/July 2016 | Unmanned Systems Technology Focus | Ground control systems A dual-screen GCS allows mapping and payload data to be handled separately for longer missions (Courtesy of UAV Factory) Manufacturers will leave an empty space inside the GCS box for the user to install their own data links for a generic system