Unmanned Systems Technology 036

96 Modular architecture This emphasis on component agnosticism runs throughout the Z1’s design. The fuselage, payloads and wings have been designed as modular ‘nodes’ that can be easily plugged in and snapped into place by hand. Each node contains a PCB and microcontroller embedded with software for monitoring and controlling its portion of flight calculations and operations. That gives not only significant free computation bandwidth for adding functions such as new autonomous manoeuvres or diagnostics, it also opens the door to modifying or upgrading each part separately, without having to perform work across the whole aircraft. For example, in addition to the nose and underbelly payload attachment points, hardpoints can easily be installed on the wings (barring any weight distribution conflicts), with the wing-based avionics boards able to operate payloads as well as receive, store and potentially process data from sensors. Aaron Camp, electrical systems engineer at Zepher Flight, says, “We want to be able to support payloads anywhere users might need them, so the nodes can interface via Ethernet, RS-232 and the many other standards our software can accept. “We use CAN as the main interfacing bus. It is a critical enabler for the nodes and modularity of our system, and helps reduce the number of wires running throughout the UAV, keeping the weight down.” Coatney adds, “The nose payload would probably be used for an EO/IR ball, while the belly payload could be a cargo hold or something with 360 º coverage, like a comms relay antenna, or Sentient Vision Systems’ Vidar or similar wide-area surveillance sensors.” Each section of the Z1’s airframe is built from prepreg carbon composite with a 1.5-2 mm foam core for strength-to- weight optimisation and durability. The company also cites prepreg carbon’s ease of use as being key to the goal of manufacturability, as it makes the Z1 simpler and less expensive to manufacture relative to wet layup, resin transfer moulding (RTM) or vacuum- assisted RTM, all of which Zepher has experience with. The airframe’s outer mould lines were specifically designed to make it easy for fabricators to make parts, as well as easier for machinists to cut the aluminium tooling itself. In particular, Zepher plans to train new fabricators to work with prepreg carbon fibre (as well as the aluminium moulds for curing to the shapes needed), which would be easier than teaching them how to work with alternative material choices. This direction is therefore expected to help considerably when scaling up the production of the Z1 and future UAVs. Maintenance Included in the USASOC’s requests was the ability to prepare and launch the Z1 as quickly as possible, while still performing all the necessary safety checks before take-off. Intelligent Energy’s fuel cell outputs real-time data for Zepher to monitor, allowing quick checks for fuel quantities and health indicators. Similarly, the batteries and servos will give digital feeds of their health statuses. With all this data readily available, Zepher anticipates being able to fully automate all pre-flight and post-recovery checks, to output quick recommendations (if any) to its technicians within a minute. The network of computer boards throughout the Z1 also enables persistent performance monitoring. For example, the wings could carry out in-flight health checks of their servos multiple times per second, with any issues being flagged up and transmitted to the technicians at the landing waypoint far ahead of time. Coatney says, “An IC engine-based powertrain would entail a lot more visual and manual checks that couldn’t be carried out digitally or automatically. “Fasteners, oil lines and cable harnesses have to be inspected for vibratory damage or looseness. Even those checks that can be made through the ECU aren’t always reliable; for example, a lot of liquid-level sensors used out there aren’t very accurate.” For refuelling, the Z1’s aft fuselage section is designed with a snap-opening February/March 2021 | Unmanned Systems Technology VTOL Proton-exchange membrane fuel cell MTOW: 25 kg Wingspan: 4.4 m Maximum endurance: 15 hours Operating endurance: 13 hours Maximum speed: 65 knots Cruising speed: 32 knots Flight ceiling: 20,000 ft (6096 m) Propulsion output: 800 W Launch & recovery: VTOL transition Some key suppliers Hydrogen fuel cells: Intelligent Energy Hydrogen tanks: HyPerComp Variable-pitch propeller: in-house Electric motors: off-the-shelf Flight management system: Applied Navigation Data links: Silvus Technologies GCS: in-house (with assistance from Applied Navigation) Specifications The Z1’s flight management system is based on the Quattro autopilot from Applied Navigation, a key development partner for the project (Courtesy of Applied Navigation)