Recent studies have shown that enabling drones to change their morphology in flight can significantly increase their versatility in different tasks. In this paper, we investigate the aerodynamic effects caused by the partial overlap between the propellers and the main body of a morphing quadrotor during flight. We experimentally characterize such effects and design a morphology-aware control scheme to compensate them. We demonstrate the effectiveness of our approach by deploying the compensation scheme on a quadrotor that can fold its arms around the main body, comparing it against the same controller without the compensation scheme. Experimental results show that our compensation scheme can address the loss of thrust due to the overlap between the main body and the propellers, guaranteeing higher tracking accuracy, without requiring complex and computationally expensive aerodynamical models. To the best of our knowledge, this is the first work counteracting the aerodynamic effects of a morphing quadrotor during flight and showing the effects of partial overlap between a propeller and the central body of the drone.
Access and exploration of confined and cluttered spaces is a major challenge in search and rescue, maintenance of infrastructures, and environmental monitoring. However, existing drones can only access passageways that are 30% narrower of their size. Herein, a drone that can squeeze its way through arbitrarily long passages that are half its width is presented. This is achieved by developing a quadrotor that synergistically embodies a soft foldable frame, multimodal mobility, and autonomous navigation. The drone exploits visual perception to detect the entrance of the gap and aerial mobility to align and fly toward it. The entry is made possible by the soft design of the frame, which passively folds without breaking when the drone flies and then collides at a controlled speed with the entrance of the passage, i.e., the “crash to squash” entry maneuver. Once inside, the quadrotor uses terrestrial locomotion for the traversal. The mechanical design of the drone and the performance of the “crash to squash” entry maneuver in passageways of different sizes are experimentally characterized. Finally, the control method is validated by indoor autonomous flights.
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