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The AVIGLE VTOL unmanned aerial vehicle, developed via collaboration by a variety of entities for a variety of applications, is shown in a wind channel test. (RWTH Aachen)

Collaborative research project leads to potentially swarming VTOL UAVs

Over a three-year period, German aerospace engineers from industry and academia collaborated on the AVIGLE (Avionic Digital Service Platform) research project, described as a "widely applicable avionic service platform" with open interfaces. Schübeler Composite contributed to the project during design via its knowledge and experience in fluid-flow machines and lightweighting, while the aerodynamic shape of the AVIGLE drone was developed at the RWTH Aachen University.

The result of the collaboration is a UAV ready for use without infrastructure, and which addresses applications such as civil security, mobile communications, construction, GIS, and surveying, but also the entertainment market and the media. For takeoff and landing the wings are tilted 90° upward, so that the two propellers—normally responsible for propulsion—are turned into rotors for hovering. As such, the UAV does not need a runway and can be used in open terrain. Flying in a horizontal line in turn has the advantage that it is more energy efficient than a helicopter flight.

AVIGLE project engineers envision the UAVs acting as a swarm of flying robots, equipped with 3-D cameras that can take high-resolution images of a region from different perspectives. This data is submitted to an evaluation system via a high-performance communication network "where a 3-D virtual world is created in quasi real time." This model can support architects and city planners but also rescue personnel at civil protection organizations under situations where there are scarce resources for short-term cellular structure of dynamic wireless networks.

Schübeler supported the project in the development, design, and production of the flight platform particularly in regard to the construction of the airframes and associated strength and weight optimizations. This among other things resulted in a wind tunnel model that was used for design evaluation. The structure was optimized during the project for revised weight, strength, and efficiency of the components. For this purpose, new manufacturing methods—non-autoclave production technologies—for composite structures were tested and implemented.

A new mechanism for the pivoting wing was developed for the UAV, which is a tilt-wing model. Schübeler undertook the evaluation and deployment of the propeller blade designs (variable pitch propeller). The development of the adjustment mechanisms for wings and propellers were also implemented to realize the adaptation of the two flight modes: floating and horizontal flight. Schübeler was also responsible for selecting and providing the energy supply as well as the development, design, and tuning of the drive components.

Ultimately the team ended up with a lightweight chassis made of carbon fiber with lithium polymer batteries. A flight time of 60 minutes at a takeoff mass of 10 kg was achieved with a payload mass of 1.5 kg. The speed of the high-wing aircraft is at most 40 m/s and it has a wingspan and fuselage length of about 2 m.

Participating in the project allowed Schübeler to expand its knowledge in the field of flow simulation and lightweight construction via its extensive research into the technological issues that came to the surface during the project. Important aspects of the know-how gained were able to be incorporated into new products and the development of existing procedures and processes. Among other things, the technical competence of the tilt-wing will be transferred to other tilt-wing and tilt-rotor projects.

Knowledge built up on the new “vacuum infusion” non-autoclave production technology during the project is likely to be implemented in the company for the production of lightweight structures. In addition, the company will use the broadband usage of lightweight composite know-how as well as the application of CFD simulation methods at different prop projects.

In the interdisciplinary research consortium Schübeler Composite collaborated not just with RWTH Aachen but also the universities TU Dortmund and Münster, the research institutes Fraunhofer IMS and IMST, as well as the high-tech commercial companies mimoOn GmbH and Aerowest GmbH. The project was subsidized by the State of North Rhine-Westphalia and the European Regional Development Fund (ERDF).

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