Unmanned Systems Technology 004 | Delair-Tech DT18 | Autopilots | Rotron RT600 | Unmanned surface vehicles | AMRC | Motion control | Batteries

62 used, although the previous target of eliminating support material for all parts built using FDM was relaxed because of the hugely complex geometry required for incorporating the power units and their control system electronics. The powered version has an FDM- built centre body, wing end ribs, elevons and wing tips again manufactured from ABS-M30. The central body incorporates two 70 mm internal diameter ducts to channel air through the EDFs, as well as mounting points for the motors, speed controller and battery, as well as an internal lattice structure for added rigidity, all within the wing’s profile. The ducts form the primary structural element of the body and offer most of the longitudinal stiffness of the aircraft as loads are transferred through their walls. Clips for the duck tail to snap on to are incorporated into the false trailing edge of the body. The central area of the upper surface of the body has a recessed opening to give access to the systems inside the aircraft. It is covered with a carbon fibre reinforced plastic (CFRP) access hatch that incorporates ducts and slotted air outlets for cooling the motor speed controllers and electronics, and is screwed into turned metallic inserts located in printed bosses. Using AM for the central body meant it could be manufactured simply by importing the CAD model to the FDM machine, although the body’s complexity meant it couldn’t be manufactured without support material providing a build platform throughout the manufacturing process. The wing skins, duck tail, intermediate ribs and access hatch are made from CFRP using vacuum infusion and a two-part resin that cures at room temperature, which eliminated the need for autoclave curing, again speeding up the manufacturing process. In order to extend the use of AM techniques to all of the UAV’s components, the CFRP parts are made from ABS moulds which themselves are built using FDM. For economy, each mould is manufactured double-sided, sealed with acetone and hand-finished to provide a smooth surface. The wings are designed to be removable, and each one incorporates a carbon spar which on assembly slides over stub spars that protrude from the central body. The inner wing ribs include a stepped edge around their periphery that engages with the body to ensure a flush fit. Custom-made carbon fibre bolts pass through the spars into threaded inserts bonded inside the centre body and fix the wings onto the aircraft. The wing tips are secured onto the wing end plates using a rubber band wrapped through a slot in the wing. This is to ensure they break away from the aircraft easily and without damage if the UAV experiences a wing landing. The duck tail clips to the rear of the central body, and offers pitch trimming and a degree of blown control due to its placement behind the EDF exhausts. The tail has a leading edge that incorporates hinge sockets and carbon fibre skins. The finished aircraft weighs 3.5 kg and has a wingspan of 1730 mm, a wing depth (centre) of 77 mm, nose- to-tail length of 700 mm, winglet height of 110 mm, elevon height of 290 mm, a maximum elevon width of 108 mm, and a maximum elevon depth of 16 mm. Power and control The body of the powered AMRC UAV houses a total of nine electronic control components, two motors and a battery. The control system is a conventional 2.4 GHz model aircraft remote control with custom control settings to allow the pilot to switch between control profiles during flights to make it easier to fly if the UAV is too sluggish or twitchy. The profiles adjust the sensitivity of inputs and the amount of movement on the control Autumn 2015 | Unmanned Systems Technology All parts of the electronic componentry inside the body of the powered version are mounted on additive manufactured brackets The software in these optimisation packages is far closer to the type of programs used in product design suites, which create smooth flowing surfaces