Unmanned Systems Technology 022 | XOcean XO-450 l Radar systems l Space vehicles insight l Small Robot l BMPower FCPS l Prismatic HALE UAV l InterDrone 2018 show report l UpVision l Navigation systems

7 Platform one Digital Aerolus has developed a new UAV incorporating its navigation algorithms to allow for more nimble indoor operations than its previous models (writes Rory Jackson). The 2.5 kg Aertos 120t is aimed at inspections in tunnels and confined spaces, and uses a fixed EO camera for forward vision, a gimballed EO camera for 360° optical sensing, an IMU and six Lidars. One Lidar faces downwards, another upwards, and the four others are pointed at intervals around the UAV to provide path measurements for navigating through tight or obstacle-laden spaces such as pipes or tunnels. Although considerable data comes in from the different sensors, the key to the indoor navigation capability is the company’s Folded Geometry (FGC) flight code. Rather than simply encompassing UAvionix has developed an FAA-certified GPS receiver that provides far higher levels of reliability than typical UAV receivers (writes Rory Jackson). The truFYX 27 g runs a receiver autonomous integrity monitoring algorithm, in which integrity quality indicators are generated continuously. These are based on the signal strength or number of satellites to allow the autopilot or pilot in command to make decisions according to the quality and reliability with which the position has been calculated. Also, fault detection and exclusion algorithms detect the ‘health’ of individual satellites in a constellation (with regard to satellite subsystems such as clocks and whether they are operating within normal sensor fusion techniques, FGC is a proprietary flight control and operating system derived from flight mathematics originally developed for space navigation, and redeployed to generate what Digital Aerolus refers to as a mathematical representation of the physical world. FGC enables all Aertos UAVs to fly stably indoors, irrespective of GPS. parameters), and remove ‘unhealthy’ ones from the overall position calculation. The algorithms are run continuously by the embedded processor on the truFYX’s board. “In the process of certifying another product, our skyBeacon general aviation transceiver, with the FAA, multiple components inside its enclosure were individually certified – including the TSO- C145d Class Beta 1 GPS receiver [now the truFYX] we developed ourselves,” said Juan Jimenez from uAvionix. The main difference between commercial GPSs used for aerial craft and an aviation-grade GPS is that the latter includes quality metrics for integrity – that is, the GPS continually tells the operator how much they can trust the aircraft’s position at any given time. An FGC-enabled unmanned vehicle polls its various sensors and uses the amassed data to calculate a geometric, algebraic space with multi-dimensional operators for roll, pitch and yaw. This provides a consistent, predictive model for the vehicle to operate by in all dimensions, rather than following the reactive models used in other autonomous navigation techniques. As the company’s Jeff Alholm explained, “From our experience, the navigation maths of unmanned vehicles in the air, on land, and on sea is fundamentally flawed. The IMUs and basic navigation tools should not be as intrinsically unstable in the absence of GPS as they are.” The 120t can fly for up to 10 minutes on a 4500 mAh battery, and if unobstructed by walls or debris it can operate up to 7 km from its GCS over a 2.4 GHz or 5.8 GHz data link. Currently, some navigation systems on air vehicles try to achieve sufficient integrity by integrating triple modular redundancy, in which majority logic gates or ‘voting systems’ check the data outputs of three navigation units, and restrict the operator’s feed to whichever output is the most prevalent. However, using three identical or closely located position sources can still yield multiple incorrect readings if the satellite signal is weak. “We’ve sought to package integrity and accuracy into a single unit for high- risk UAS operations such as beyond visual line of sight, controlled airspace or operations over people,” Jimenez said. “Integrity is a specific GPS concept, and it gives you a much better means to predict whether to continue or discontinue a mission than accuracy metrics alone.” Nimble indoor movement ‘Integrity’ GPS receiver Airborne vehicles Navigation Unmanned Systems Technology | October/November 2018 A proprietary flight control system gives the Aertos 120t greater agility indoors and in confined spaces