100 A variety of configurations have been used and iterated upon by Skygauge’s team. Currently, two rotary servos hold up each coaxial rotor pair, and tilt them around their respective axes using what Korol terms “a four-bar linkage”, enabling them to pan and tilt as a gimballed camera might, without modifying their position in the airframe. Each servo pair and motor pair operates independently of the others, enabling different adjustments, based on the aforementioned sensor data feeds. “Programming those systems to all work correctly across different wind conditions was extremely challenging, especially getting the servos to tilt the rotor pairs in correct responses against wind and torque numbers. We do in-house testing and validation, where we strap each UAV down and run it through every conceivable permutation of articulations, with laser measurements to check that it is, for instance, tilting its rear-right thruster exactly 30° when we want it tilting 30°,” Korol notes. “An undervalued part of this whole challenge was the stiffness we needed out of the airframe. We had to engineer all the carbon composite and aluminium parts across the body, over many iterations, to absolutely minimise flexing of any part of the assembly, because if the airframe starts flexing, it changes the positions and dynamics of the drone considerably. The end result is that we get less than a millimetre of deviation from its position in any direction.” Cable management was another key development challenge. “There are no slip rings for now, thankfully; slip rings can be tough to work with. But routing of the cables for every motor and servo is important, and many of our early failures in our design iterations, particularly during stress testing, would come from wires getting sheared and chewed on the corners of subsystems,” Korol recounts. “Since then, we’ve made a lot of provisions in the mechanical design to keep that from happening, and to make it easier to inspect and replace cable harnesses quickly too. Thankfully, we’ve not had another wire-jacket failure like that in quite some time.” Swap and relaunch Typically, the UAV keeps flying until the battery’s state of charge (SoC) drops enough to merit landing. In addition to the aforementioned laser rangefinder and camera for forward measurements, a second, downward-pointing pair of laser and camera sensors are used to ensure safe landings (the laser can also enable altitude measurements if the path to the ground is clear of objects). February/March 2024 | Uncrewed Systems Technology In operation | Skygauge UAV ultrasonic inspections Programming intelligent rotor responses, engineering sufficient airframe stiffness and smart cable management were all crucial to making the UAV hold still during physical inspection Other tasks being slated to be handled by the Skygauge UAV include pressure washing, rust removal, industrial welding and the application of coatings across buildings, ships and other constructions
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