FIXAR 025 | Digest and redundancy for navigation in flight together,” Fainveits says. “Thanks to those estimation algorithms, the system can be GNSSdenied, and still remain capable of controlled flights and of completing most missions. We have also tested VectorNav’s inertial solutions and they present promising results, but we’d just need some further customisation and adjustments first.” Those state estimation algorithms, as well as the 025’s aforementioned software-control loops, are key to how the UAV automatically senses and adjusts its control behaviours to account for changes in weight distribution – and hence changes in the CoG – derived from individual users’ different payload arrangements and changes in aircraft orientation during flight. As Fainveits explains: “Having those adaptive characteristics is vital for going from ‘automatic’ to truly autonomous flight. Say, for example, you have a multicopter working in a delivery application carrying a parcel for someone as its payload, and it is controlled by some off-the-shelf autopilot running Pixhawk control software. “When it’s carrying its package it has one specific PID [proportional-integralderivative] controller setup; when it drops off its payload it must be triggered to shift into a different PID setup to account for the changes in weight, CoG and centre of balance. “That’s a bottleneck of automated UAVs versus autonomous UAVs. If you don’t trigger that specific PID setup after the change in the CoG, then the UAV won’t be stabilising itself correctly and won’t fly safely. But, with the FIXAR 025, you put on your payloads, plan your mission waypoints and the system automatically adapts how it controls itself, with very quick reaction times to inertial data coming in at every flight stage.” Payload integration itself takes some mechanical, electrical and software integration, including bridging PWM, TTL or UDP logic control between payloads and the autopilot, as well as API-to-API management (TTL, PWM and UDP is installed in the autopilot by default). This can take significant back-and-forth between FIXAR and payload vendors. Fainveits recalls one instance where a camera meant for gimbal pointing and target tracking repeatedly calculated targets’ coordinates incorrectly. He recounts: “In summary, that happened because the camera was a two-axis system, trying to operate in a 3D mission. Fixing that is simple maths: ‘multiply it to the tangents of this angle’, we essentially said to the vendor. They did that, sent back an improved version, we tested it and found issues we didn’t catch the first time, they made fixes for it, and after two months we got the camera working nicely. “But it hugely comes down to whether the vendor responds in good time, and is willing to either implement our changes, or let us make changes ourselves.” Lidar One more important feature, which brings autonomy, is the realtime surface-tracking system and autonomous altitude adjustment to the MOCA (minimal obstacles clearance altitude). As mentioned, a Lidar is installed under the fuselage to further the autonomy of the 025. The 3D Lidar measures terrain and objects below and around the airframe. One function of this system is to track the yaw and roll of the aircraft to aid the inertial sensors’ own measurements in informing the adaptive autonomy algorithms. Its more important function, says Fainveits, is to track for surface objects such as trees and buildings ahead to undertake obstacle avoidance manoeuvres. BVLOS surveys of regions not recently or previously mapped will especially need such intelligent reactivity to avoid controlled flights into structures, trees or terrain, in the absence of pre-existing 3D map data to use during mission planning (FIXAR has been previously instructed that such information is not always available in a useable digital format). The Lidar sensor used for adaptive autonomy comes from LightWare LiDAR. Key factors for its selection include supply chain security and resilience, and more importantly, highly accurate and detailed measurements amid interference stemming from environmental factors. FIXAR says the laser scanners of RIEGL, YellowScan and TopoDrone are used for laser scanning and mapping missions to generate 3D point clouds after some software processing. All onboard Lidar systems are installed in a way that maximises the width FoV, meaning close to zero occlusions from the body or airframe. “As you know, the Latvian climate is very prone to snowy winters, and much of what we do is close to or over the shores of the Baltic Sea, which means it’s easy for us to test how optic-type sensors perform in environments where there’s a lot of reflections going on,” Feinveits says. “When we speak about the most critical sensors, which are Lidar sensors, we put much attention to real 111 Uncrewed Systems Technology | February/March 2025 Its more important function is to track for surface objects such as trees and buildings ahead to undertake obstacle avoidance manoeuvres
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