Uncrewed Systems Technology 043 l Auve Tech Iseauto taxi l Charging focus l Advanced Navigation Hydrus l UGVs insight l MVVS 116 l Windracers ULTRA l CES 2022 show report l ECUs focus I Distant Imagery

39 factory, and driverless cars. These are using innovative techniques to connect charging pins to the vehicle, coupled with the vital monitoring and safety circuitry. Wireless technology comes into its own though in harsh environments and with dynamic charging. Supplying power while in the air or while driving overcomes many of the charging issues but requires far more infrastructure. Wired charging The demand to get more power into a UAV when charging has led to the development of techniques to automate connector-based charging systems. This has partly been enabled by more accurate positioning systems that can place a system on a specific area, and smaller, lighter charging and comms designs. One such system uses a landing pad that is a 6 x 6 matrix of charging points. These are connected to a power controller and power supply via nine wires in a multicore cable. Five spring-loaded contacts on the UAV can land on the grid. Each pin can handle currents of up to 10 A, for a theoretical maximum of 50 A, with a voltage up to 60 VDC, although the landing pad is capable of 15 A. The system can detect if two contacts land on the same pad and activate only one, and just activate the pads that are in contact with the UAV. This allows the UAV to land in any orientation on the matrix pad. The key is the controller in the UAV, which can weigh as little as 16 g and supports a range of UAVs and battery chemistries, from lithium-polymer and lithium-ion to lithium phosphate, nickel metal hydride and even older nickel cadmium cells. With a high-precision navigation system that provides a positioning accuracy of 2-20 cm, the UAV can land on a simpler pad with two 20 x 20 cm pads. In this case the system can handle currents up to 30 A, with a voltage up to 60 VDC. This system uses two types of detection. Capacitive detection is the lightest, and uses a capacitor with a known value. When the contacts are connected, that changes the system capacitance, which is picked up by the controller. This allows the UAV to land safely in an emergency, as the capacitance will not change if it lands on an inert surface, but it is capped at 20 A for a 750 W system. Another approach uses power line comms (PLC). This is a larger box, as it includes the PLC’s modem for sending data to the charging system. This data identifies the UAV and, based on the data, dynamically adjusts the charging for a specific battery – if no data is received, the charging system stops. This supports power charging rates of up to 2500 W, but at 24 g it weighs more. The detection sequence allows any data to be sent via the PLC modem to the charger, for example to allow a BMS to use state- of-health data. The controller in this system has Battery charging | Focus Unmanned Systems Technology | April/May 2022 This robotic charger system is being tested with Einride’s unmanned vehicle (Courtesy of Siemens Technology) A capacitive detection system avoids the risks of short-circuits with a pinned UAV charging system (Courtesy of Skycharge)