A Novel Morphing Quadrotor UAV with Sarrus-Linkage-Based Reconfigurable Frame

Nature provides a repertoire of flyers demonstrating dynamic maneuvering during flight by effectively using their morphological changes, thus adapting to environmental variability. However, most conventional multirotor Unmanned Aerial Vehicles (UAVs) use rigid and single-configuration platforms, limiting their adaptability to environment and task changes. To address this limitation, this work proposes a novel morphing quadrotor UAV with a reconfigurable frame capable of changing its size during flight. The reconfigurable frame integrates two coplanar parallelogram four-bar linkages into each limb of a four-sided Sarrus linkage. This leads to a single degree of freedom (DoF) parallel mechanism with a symmetric structure, which ensures the four motor arms are coplanar and always with the same length while the morphing quadrotor UAV size changes. Based on this design, we investigate the feasibility of the morphing quadrotor UAV by building a proof-of-concept prototype that can change its size from a maximum of 410 mm to a minimum of 310 mm, meaning it can reduce the size by 24.4% and actively adapt to changing environment during flight. The in-flight morphing test shows that the morphing quadrotor UAV can implement a stable flight at various sizes. The experimental tests also demonstrate the potential for deploying the morphing quadrotor UAV in applications where the robot needs to navigate through narrow openings.