| Reconfigurable systems are systems that can be transformed into different configurations, to provide different functionality or to adapt to different operating environment. In this paper, we describe the preliminary design process and construction (and challenges faced thereof) of a first generation modular Unmanned Aerial Vehicle (UAV) that is reconfigurable offline. The modules of this reconfigurable UAV platform can be assembled to form a quad-rotor UAV (QR-UAV) configuration or a fixed-wing UAV (FW-UAV) configuration, respectively providing VTOL/hovering capabilities and long-endurance/range capabilities. The goal of this design effort is to develop, fabricate, and flight-test a modular /reconfigurable UAV platform that can be used by different types of field personnel---from wildfire firefighters, to emergency responders and-post-disaster search and rescue teams. Potential end applications could be forest fire mapping, search for survivors post disaster, and providing situational awareness in an emergency. The UAV modules were defined in terms of 15 design variables, and the conceptual design optimization was performed using the mixed-discrete Particle Swarm Optimization algorithm.;The QR configuration in this UAV comprises four ducted rotors and a central pod housing all the required electronics, including the battery. In addition to all the modules in the QR configuration, the FW configuration includes a multi-section flying wing with vertical and horizontal stabilizers, where the ducted rotors are mounted on the bottom (1st generation concept) or the top (2nd generation concept) of the wing. The latter strategy was adopted in order to deal with ground clearance issues, and allow belly landing of the FW configuration. In developing the detailed design, it was conceived that majority of the fabrication will be performed using additive manufacturing techniques, except for the wing sections and the off-the-shelf components (e.g., motor and rotor blades). The design and performance requirements however demanded both ease of assembly and robustness of the assembled platforms, which tended to be conflicting objectives when performing the preliminary design/fabrication of the inter-module interfaces. Several attachment mechanisms were explored in order to promote swift assembly/disassembly. For the first generation concept, push-fit/press-fit mechanisms were implemented for module interfaces. However, after a preliminary fabrication/flight-testing iteration, several improvements were deemed necessary to produce a more secure attachment of the modules. More specifically, in the 2nd generation concept, a new sliding attachment/interface along with a locking mechanism was developed for increased robustness without compromising ease and speed of assembly. The preliminary design/fabrication/flight-testing processes has now provided us with new constraints that would be implemented in the overall design optimization of the next generation of this reconfigurable UAV platform. These constraints (particularly those related to module interfaces) are generally not realized at a conceptual design stage, and their quantification and categorization performed here will help create a foundation for future modular platforms for small reconfigurable UAVs. |
