Unmanned Systems Technology 027 l Hummingbird XRP l Gimbals l UAVs insight l AUVSI report part 2 l O’Neill Power Systems NorEaster l Kratos Defense ATMA l Performance Monitoring l Kongsberg Maritime Sounder

42 Focus | Gimbals have no particular benefit if the camera is always slightly off. With that in mind, this level of integration requires that the autopilot’s interface control document, which contains the comms language and requirements of the device, be shared with the gimbal manufacturer. That enables pertinent data to be sent and received by both systems, but requires that the autopilot and gimbal developers collaborate to create a driver for powering that. For more help with identifying and tracking targets, a new type of UAV gimbal design integrates a series of small cameras around its base, along with software-based ‘stitching’ of their video feeds, for a 360° panoramic view about the aircraft. Advances in miniaturised smartphone cameras (and wide-angle lenses) can be exploited to prevent the panoramic cameras enlarging the gimbal base. When combined with the latest image processing systems, such a gimbal can be programmed to identify a range of different targets in all directions beneath the UAV, and prioritise them according to context-specific markers. The main EO/ IR turret can then be pointed towards that prioritised target to zoom in on it and run further analytics to determine the next course of action. Optics Selecting the right gimbal window depends on the sensor, with the material being chosen to match the waveband in which the sensor performs best. The key is to be unable to notice any difference in the payload imagery whether the window is there or not. Optical-grade glass is commonly used for RGB day cameras, with coatings optimised for minimal reflection and high durability. Germanium is widely used for thermal cameras, as it provides very good transmission of MWIR and LWIR imagery. Silicon is also used in some gimbals with MWIR cameras (being relatively less costly than germanium), with further coating for 3-5 µm wavelengths. Diamond-like carbon is particularly suitable as an IR coating for UAVs used for flying through sand, moisture or other sources of interference owing to its durability, although it tends to transmit 5-10% less IR light than other anti- reflective IR coatings. For laser rangefinders, optical-grade glass with coatings specialised for wavelengths between 900 and 1550 nm are typical. Different grades of optical sapphire are used for different wavelengths, from visible light through to SWIR and laser systems. Typical fabrication of sapphire windows involves ring polishing, a single- sided process that takes about 14-18 weeks to achieve minimal roughness, parallel surfaces on either side of the window, and high transmission of visible, IR or laser light. However, proprietary methods exist for double-sided polishing of sapphire windows, which can shorten lead times to between five and six weeks. Sapphire provides far higher durability than most other optical materials, and with a coating it will last much longer August/September 2019 | Unmanned Systems Technology Cameras can be installed around the base of a gimbal to provide a 360 º view for enhanced awareness and object detection (Courtesy of UAV Components) Highly accelerated stress screening can be used to unearth a gimbal’s likeliest eventual point of failure, and correct it, before repeating the process for further testing and optimisation (Courtesy of UAV Factory)