Abstract
Nature-inspired free rotors, such as monocopters and other self-revolving wings, exhibit promising potential across numerous applications. Unlike traditional multirotors and fixed wings, the free rotors generate lift by rotating their winged body, enabling both efficient hovering and vertical takeoff and landing capabilities. While previous studies have showcased interesting prototypes and demonstrations, the practical deployment of free rotors remains challenging due to their limited payload capacity, insufficient control authority, and constrained locomotion ability.
To this end, this thesis provides several solutions focusing on scalability, adaptivity, and transformability, with the aim of expanding the application scope of free rotors. Through the scalable design, free rotors can be repetitively disassembled and reconstructed into various flight configurations to meet specific task requirements such as payload capacity, mission duration, footprint, and customized flight equilibrium. The adaptivity provided by the passive-compliant airframe and adaptive flight controllers enables enhanced control authority even with varying payload weights during flights. Additionally, transformability facilitates bi-directional in-flight transitions between quadcopter mode and free rotor mode, allowing the proposed robot to attain flight agility, hovering efficiency, and expanded tasking range capabilities. To achieve those goals, detailed dynamic modelings are studied and practical flight stabilization laws are considered. In addition, several experimental prototypes are designed and fabricated to assess the designed strategies across a range of flight scenarios.
The experimental findings validate the feasibility of the proposed approaches. In the scalable design, a total of 12 possible combinations, including both symmetric and asymmetric configurations, are selected and tested. All configurations demonstrate stable flights, with an average position error of 8.9 cm. While, the adaptive design shows improved control authority when a potential payload is attached. With optimal pitching angle, the developed vehicle achieves 56.8% more power loading than using propellers directly, from 4.4 to 6.9 g/w. The transformable free rotor offers flight agility, hovering efficiency, and a wide field of view (FoV). Its improved tasking ability is further showcased through tasks such as displaying a 2D image using an LED light strip and conducting omnidirectional surveillance with a single camera.