111 Both Sensus L4 and Sensus L8 have a typical maximum speed of 25 m/ sec (90 kph) and resist wind speeds as high 18 m/sec (64.8 kph). This difference might seem anomalous, but any multicopter’s top speed is self-generated motion in controlled conditions, while wind resistance is a battle against external forces, often requiring much more power and control effort to remain stable. Hence, the top speed is typically higher than the maximum wind speed it can resist. In light of this, ISS has long worked with Arducopter developers to make sure that the system is tuned to all of its envelope limits. “Therefore, to the operator, the system behaves in the same way at both ends of the environmental conditions scale,” Kempley emphasises. Navigation and collision prevention Sensus L features dual redundant RTK GNSS GPS receivers for precise navigation, a system based on active sensors for obstacle detection and avoidance, a 200m laser altimeter for accurate measurement of the vehicle’s height above the terrain, and a Mode S ADS-B transceiver for enhanced air traffic awareness. The laser altimeter enables terrain following flight in which the vehicle maintains a consistent height above the ground while following a route planned within the ground control station. “Depending on the customer’s configuration, this can use both dual laser and dual radar altimeters for precise and redundant control,” according to Kempley. The active obstacle avoidance system combines a laser, a radar and an infrared time-of-flight (ToF) sensor. This, Kempley says, enhances the vehicles’ ability to navigate safely in complex environments and inside buildings etc, while having enough breadth of sensor types to mitigate varying environmental conditions. “Running real time RL/AI routines, the system can learn the environment and understand where obstacles are after first encounters,” Kempley explains. “This means it can then iterate faster during complex exploration. It is then still capable of seeing ad-hoc and new obstructions as well as dynamic obstruction scenarios. Feeding back into the model to improve its understanding of the local environment. If running in swarms, this can then be shared with its cohorts, forming a data driven mesh of exploration.” The navigation system also supports navigation in GPS-denied environments using a variety of technologies including external aids, integrated sensors and advanced software-based techniques. These can include infra-red (IR) and radio frequency (RF) beacons in controlled, localised operations. Such beacons support precise position holding and guided movement, albeit with the limitation of requiring pre-installed infrastructure. Another capability is visual inertial odometry (VIO), which uses a combination of maps, cameras and inertial measurement units (IMUs), although its navigation accuracy is tied to the quality of the available maps and on lighting conditions. When no maps are available, the system can use simultaneous localisation and mapping (SLAM) algorithms to process sensor data, relying on high levels of processing power. Finally, high-grade inertial navigation sensors enhanced with radar velocity detection give very accurate results, although only for short periods as they are subject to drift with time. Using either GPS with RTK or beacons, Sensus L can achieve take-off and landing accuracies of better than 10 cm, Kempley notes, adding that these systems can be augmented with AprilTags (similar to QR codes) and optical cameras to find and home in on its touchdown location. “Additionally 360 degree radar/laser sensors can alert the system to obstructions in the area during these phases.” Communications agnostic Using IP-based networking, the Sensus range is essentially communications agnostic, meaning any type of UDP/TCIP radio system will work out of the box, according to Kempley. However, ISS often uses data links from Codan company Domo Tactical Communications (DTC). All the links used on the vehicles offer encryption options up to AES256, Uncrewed Systems Technology | April/May 2025 Mounted in the centre of the composite ring structure on this Sensus L8-H2 is a Fuel Cell Power Module from Intelligent Energy, which provides up to 150 minutes of flight
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