Bio-inspired Mechanical Intelligence for Aerial Systems: Stabilizing Aerodynamic Dampers for Cooperative Transport and Reconfigurable Tensegrity-Origami Structures for Morphing and Perching

Abstract

This thesis investigates bio-inspired, mechanically-intelligent solutions to address two challenges in aerial robotic systems. The first part of this research focuses on the usage of aerodynamic dampers for stabilizing the cooperative transport of a suspended payload by multiple aerial robots. The second part investigates the design for reconfigurable tensegrity-origami structures that facilitate morphing and perching in cluttered environments for flying robots.

This begins with the problem of stabilizing multiple aerial robots that cooperatively transport a cable-suspended payload. Due to the limitation on payload capacity and computational power for minimal aerial robots, this study devises lightweight air dampers that inherently stabilize the multi-agent system at its equilibrium state, instead of relying on global navigation satellite systems (GNSS) or vision and communication for agents to actively estimate and control the state of the multibody dynamics. This permits the robots to safely carry a load at a constant velocity without additional state estimation or active correction. The proposed framework is proven stable and verified by simulations and extensive flight experiments. Lightweight mechanical dampers (under 7 g) are shown to be effective in attenuating undesired oscillations and overcoming disturbances. To this end, a team of four robots cooperatively transporting a payload over 20 m in open space is demonstrated, and three robots safely transporting a point-mass payload over a distance of 45 m outdoors. The promising outcomes highlight the benefits of the passive strategy, which demands minimal hardware components and computation to realize the sophisticated aerial transport task.

The second part of the study concerns physical intelligence for reconfigurable airframes of aerial robots, based on tensegrity structures which are known for their compactness, resilience, and lightweight properties. While these structures have been extensively studied for integration with robotics, their application in aerial robotics has been limited to protective shells. In this study, we innovate upon the traditional tensegrity and introduce "tensegrigami" designs, incorporating origami-inspired revolute joints. This adaptation involves replacing the typical isolated rigid struts with revolute angled struts, creating a self-stabilizing structure facilitated by pre-stretched elastic components. This thesis derives the principles of structural integrity and equilibrium conditions for these tensegrigami structures. Leveraging these principles, we design and fabricate airframes that endow aerial robots with capabilities for morphing, thrust vectoring, and perching. Notably, during flight, the tensegrigami robot can reduce its width by 52%, allowing the robot to navigate through narrow gaps. The closed-shape structure and in-tension nature of tensegrigami also enable the robots to perch in cluttered environments. The experiments validate the tensegrigami structure's reliability, robustness, and versatility as airframes for small aerial robots, highlighting their potential for operation in complex natural settings.

In summary, this thesis proposes intelligent mechanisms for enhancing small-sized aerial robotic systems. The introduction of stabilizing dampers for cooperative transport by a team of minimal robots eliminates the need for additional sensors and active corrections. Furthermore, the development of tensegrity-origami inspired reconfigurable structures effectively endows aerial robots with the capabilities of morphing and perching in cluttered conditions.

Date of Award	17 Sept 2024
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Pakpong CHIRARATTANANON (Supervisor)