Unmanned Systems Technology 015 | Martin UAV V-Bat | William Sachiti | Sonar Systems | USVs | Desert Aircraft DA150 EFI | SeaCat AUV/ROV | Gimbals

27 Martin UAV V-Bat | Dossier trajectory commands for acceleration and heading are generated, which are then used to generate corresponding commands for roll, pitch and yaw for the control vanes in the V-Bat’s duct. The location, altitude and heading for the outbound transition manoeuvre can be specified before the control algorithm is initialised. Once the trajectory and vane commands have been executed, the V-Bat’s ground speed must increase until the sensed airspeed exceeds the stall speed by a logical margin. When that is achieved, the transition into horizontal flight is completed, and a high-speed flight control algorithm takes over from the transition control algorithm. Recovery strategy Once the mission is completed, the V-Bat’s recovery involves using many of the same principles as outbound transition but in reverse, such as the generation of trajectory commands towards deceleration rather than acceleration. The location of the landing zone is stored and used during recovery to determine the heading, ground speed and altitude of the inbound transition, such that the manoeuvre finishes at the coordinates at which the launch took place. The same inbound transition control algorithm used for landing could be exercised in mid-flight by the user to switch to a ‘hover and stare’ mode during ISR missions, where more precisely targeted imagery is required. Optimising the methods for outbound and inbound transition required a few minor configuration changes between versions 1 and 2 and 3. By and large, however, Dr Morris’ pre-2015 V-Bat design was what made the transition a possibility from the beginning. For the most part, the UAV is balanced like a conventional aeroplane. The centre of gravity is given as about one-third of the mean aerodynamic chord back from the leading edge of the wing, making it positively stable when engaged in horizontal fixed-wing flight. If the in-house developed autopilot algorithms make up one half of the Unmanned Systems Technology | August/September 2017 cylindrical shroud. The propeller also provides cooling for the motor, air being drawn in over the rim of the duct, filtered and forced through the engine. Below the propeller are the eight control tri-vanes attached to their eight radially arranged stator rails, which connect electronically to the autopilot for command functions. Each vane operates independently of the others with its own digital servo. The generator is installed atop the engine, and the engine control unit is located above the generator, just above the fuel tank. The fuel tank cannot be removed from the lower fuselage – this section’s cube-shaped hull walls and upper and lower bulkheads constitute the fuel tank itself. An additional layer of epoxy is coated inside these bulkheads. The wings are carbon fibre monocoque parts with fibreglass skin, produced as hollow shapes and each supported by four structural spars that extend from the lower fuselage. During assembly, each wing slides over the spars, and wiring must be run through to provide necessary power for the wingtip lights, aileron servos and data links for video telemetry. The cylindrical upper fuselage has a single carbon-Kevlar bulkhead at the top of the section. Just beneath it, careful placement of avionics and batteries provide balance weight to help keep the centre of gravity at one- third mean aerodynamic chord. The upper fuselage also contains all the crucial avionics, including pitot and static sensors, inertial navigation sensors, GNSS and autopilot board. No direct cooling system is used for the electronics; instead each system is mounted on heat sinks, with cooling ducts avoided to maximise environmental sealing. The nose section contains a lead weight, as a primary ballast, and the payload. Different noses contain different sensors, and each can be swapped in and out depending on mission requirements. To assemble the V-Bat, each section is constructed with an offset measured to enable an interference fit, to slide over the skin of the section beneath it and hold it in place through friction, before being locked using Mil-Spec (mostly hex-head) fasteners. Each screw has a backing plate on the interior for sealing against the environment. Some key suppliers to the V-Bat Avionics: Advanced Navigation Raw fabric materials: The Composites Store Additional raw materials: Grainger Connectors and wiring: Digi-Key Wiring harnesses: Lemo Fasteners: McMaster-Carr and Chief Aircraft Shipping cases (vehicle storage): Go Professional Cases Communications: Haigh-Farr Persistent Systems Antenna and cables: GPS Source Propellers: Mejzlik Modellbau Motor: Hirth Engines and NWUAV Servos: MKS Servos USA, ServoCity and Volz Motor and camera vibration isolator mounts: Modus Advanced Tooling plastics: Tap Plastics US Plastic Corp Circuit boards (fabrication house): Sunstone Circuit boards (assembly house): World International PCB Additional hardware: Aircraft Spruce & Speciality The Flight Shop