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

63 AMRC | Dossier surfaces for given inputs. The servos for the control surfaces are high-torque ball raced components that clip directly into the elevons, without brackets or cables, and control the tail using a custom additive manufactured linkage. The elevons are designed with slide-in hinges to connect with servo-actuated hinges. The UAV is powered by two 70 mm 3200 KV electric motor-driven ducted six-blade fans controlled by two 80 Amp speed controllers, all running off a single 3000 mAh lithium-polymer battery. It also incorporates space to carry two lithium-polymer batteries in the airframe to extend flight time if required. The fans give a combined thrust of 25 N. No gyro- stabilisation or autopilot systems are used during flight as they would mask the UAV’s flight characteristics and mean that any imperfections in construction would be concealed. Optimisation Topology software, from Altair’s Hyperworks suite, was used to develop the central body of the powered UAV. The software allows the team to create design parameters and input the effective loads acting on the body during flight, and optimise the material distribution in order to support these loads. It then redesigns a new CAD model and runs a finite element analysis on it to compare it with the original design. The software can also show the best design solution for weight reduction, higher stiffness and lower stresses. This has to be interpreted by an engineer to determine the ideal build solution for a particular manufacturing technique. Bull says, “AM offers huge scope for optimisation that conventional machining and other manufacturing processes cannot give. Using topology software, the user can make an organic skeletal structure inside a component that carries the load in the most efficient way and supports only those areas in the structure that need it, lightening the design. It can also be used to optimise the aerodynamic flow over a surface as it helps with the morphing of structures, and using this software can optimise the aerodynamic design.” The two Hyperworks programs used by the DPG are Hypermorph and OptiStruct. These allow the team to build virtual experiments and deform the surfaces of a component to analyse the aerodynamic flow over it while also analysing the internal structure of the components. One problem being evaluated is the design of the EDF ducts on the UAV’s upper surface. These have a very flat top surface that is not ideal aerodynamically, and after running the CAD design through Hypermorph using a 2D cross-section, the team was offered an optimum geometry and angle of attack for the wing and duct profile. This was confirmed following analysis of the new design using computational fluid dynamics (lower image, above). Keith Colton, research and development engineer at the DPG, remarks, “In the whole Hyperworks suite you can constrain things like the UAV’s centre of gravity, and the software will optimise the structure to incorporate the centre of gravity and adjust the location of things like the payload position and propulsion systems around it, keeping it constant. Traditional CAD packages are great at traditional subtractive manufacturing, but the software used in these optimisation packages is far closer to the type of programs used in product design suites and animation packages, which create smooth flowing surfaces. “The tools we use with this are more like sculpting, where you would start off with a piece of clay and mould it into the shape that the topology suggests. It makes the system far more organic in its design approach and it understands that these components are going to be grown. These tools are early in their use and have so far only been deployed in very high-end aerospace applications. Once a complete optimisation Unmanned Systems Technology | Autumn 2015 The optimum aerodynamic profile for the top of the EDF ducts was produced by the optimisation software and analysed using CFD