A Passive Aeromechanic Approach for Collision Avoidance of a Reconfigurable Multirotor Robot

Project: Research

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With foreseeable applications such as reconnaissance and transportation, research in small, human-friendly micro aerial vehicles has received tremendous attention from scientists and engineers. These small robots have the potential to revolutionize our use of robots for civilian applications. Autonomous flight and navigation in complex, constrained environments, however, remains a major technical barrier. The issue is exacerbated in small platforms with severely restrained payload and computation power. Current approaches towards collision-free flight largely make use of sensors to map the environment and surrounding obstacles. State-of-the-art methods usually concern visionbased localization or optic flow-mediated algorithms for state estimation, planning, and flight control. Complementary to these detection and mapping strategies, lightweight protective structures and mechanically resilient airframes have been developed for flying robots to cope with impacts from collisions or subsequent falls. Thus far, the roles of sensing and estimation methods for obstacle avoidance and resilient mechanisms for impact mitigation are distinctly separated. In this proposed research, we introduce an aeromechanical method that enables a flying machine to passively avoid a collision without the need for direct sensing or demanding computation. This research will address the issues of reactive navigation of small aerial robots with limited payload and computational resources in three steps. First, to induce a mechanical response when the robot flies near a vertical surface, the vehicle employs ducted propellers that are tilted inwards. Our preliminary measurements indicate significant interactions between the downstream wake and a proximate wall. In the flight setting, this results in a visible change in the horizontal thrust component that passively stabilizes the robot at some distance away from the wall even in the absence of position feedback or control. Second, the analysis of the attitude dynamics and propeller commands, when combined with the aeromechanic model describing the propeller-surface force, leads to a simple observer for obstacle detection. Consequently, an efficient flight scheme based on a contactless wall-following strategy is devised to establish a reactive navigation strategy for small aerial vehicles. Finally, we propose to reduce the adverse consequence on flight energetics caused by the use of tilted propellers through the development of a transformable airframe. The reconfigurability lets the robot assume a conventional propeller arrangement for energy conservation when it operates in safe environments, or take a configuration with tilted propellers for collision-free flights in cluttered space. It is perceivable that the proposed research will contribute to advances of micro aerial robots by the introduction of the mechanism-based navigation strategy and broadening the applications of small aerial vehicles. Scientific merits will come from (i) the improved understanding of propeller-surface aerodynamic interactions or proximity effects in the context of multirotor vehicular dynamics; (ii) the development of a novel reactive navigation strategy with minimal sensing and computational requirements; and (iii) the use of reconfigurable structures to enable improved flight endurance and collision avoidance capability in small multirotor vehicles. 


Project number9043146
Grant typeGRF
Effective start/end date1/01/22 → …