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Principles & Applications of Insect Flight

thesis
posted on 14.12.2020, 22:38 by Jesse A Roll

Insects are the most successful animal on the planet, undergoing evolutionary adaptions in size and the development of flight that have allowed access to vast ecological niches and enabled a means by which to both prey and escape predation. Possessing some of the fastest visual systems on the planet, powerful sets of flight muscles, and mechanosensors tuned to perceive complex environments in high-fidelity, they are capable of performing acrobatic maneuvers at speeds that far exceed that of any engineered system. In turn, stable flight requires the coordinated effort of these highly specialized flight systems while performing activities ranging from evasive flight maneuvers to long-distance seasonal migrations in the presence of adverse flow conditions. As a result, the exceptional flight performance of flying insects has inspired a new class of aerial robots expressly tailored to exploit the unique aerodynamic mechanisms inherent to flapping wings. Over the course of three research studies, I explore new actuation techniques to address limitations in power and scalability of current robot platforms, develop new analytical techniques to aid in the design of insect-inspired robot flapping wings, and investigate attributes of flapping wing aerodynamics that allow insects to overcome the difficulties associated with flight in turbulent flow conditions, in an effort to advance the science of animal locomotion.

Recent advancements in the study of insect flight have resulted in bio-inspired robots uniquely suited for the confined flight environments of low Reynolds number flow regimes. Whereas insects employ powerful sets of flight muscles working in conjunction with specialized steering muscles to flap their wings at high frequencies, robot platforms rely on limited sets of mechanically amplified piezoelectric actuators and DC motors mated with gear reductions or linkage systems to generate reciprocating wing motion. As a result, these robotic systems are typically underactuated - with wing rotation induced by inertial and aerodynamic loading - and limited in scale by the efficiency of their actuation method and the electronics required for autonomous flight (e.g., boost converters, microcontrollers, batteries, etc.). Thus, the development of novel actuation techniques addressing the need for scalability and use of low-power components would yield significant advancements to the field of bio-inspired robots. As such, a scalable low-power electromagnetic actuator configurable for a range of resonant frequencies was developed. From physics-based models capturing the principles of actuation, improvements to the electromagnetic coil shape and a reconfiguration of components were made to reduce weight and increases overall efficiency. Upon completion of a proof-of-concept prototype, multiple actuators were then integrated into a full-scale robot platform and validated through a series of free flight experiments. Design concepts and modeling techniques established by this study have since been used to develop subsequent platforms utilizing similar forms of actuation, advancing the state-of-art in bio-inspired robotics.

With the ability to make instantaneous changes in mid-flight orientation through subtle adjustments in angle-of-attack, the maneuverability of flying insects far exceeds that of any man-made aircraft. Yet, studies on insect flight have concluded that the rotation of insect wings is predominately passive. Coincidentally, bio-inspired flapping wing robots almost universally rely on passive rotational mechanisms to achieve desired angles-of-attack - a compromise between actuator mass and the controllable degrees-of-freedom that results in underactuated flight systems. For many platforms, the design of passive mechanisms regulating the rotational response of the wing is determined from either simulations of the wing dynamics or empirically derived data. While these approaches are able to predict the wing kinematics with surprising accuracy, they provide little insight into the effects that wing parameters have on the response or the aerodynamic forces produced. Yet, these models establish a means by which to both study insect flight physiology and explore new design principles for the development of bio-inspired robots. Using a recent model of the passively rotating insect wing aerodynamics, a novel design principle used to tune the compliance of bio-inspired robot wings is developed. Further, through the application of nonlinear analysis methods, parameters optimizing lift production in flapping wings is identified. Results from this analysis are then validated experimentally through tests preformed on miniature flapping wings with passive compliant hinges. This work provides new insight into the role passive rotational dynamics plays in insect flight and aids in the development future flapping wing robots.

Insect flight is remarkably robust, enabling myriad species to routinely endure adverse flow environments while undergoing common foraging activities and long-distance migratory flights. In contrast to the laminar (or smooth) flow conditions of high-altitude flights by commercial aircraft, insect flight occurs within the lower atmosphere where airflows are unsteady, and often turbulent. Yet despite the substantial challenge these conditions pose to an insect's physiology, flights spanning entire continents are common for numerous migratory species. To investigate how insects sustain stable flight under fluctuating flow conditions, the aerodynamic forces and flows produced by a dynamically scaled robotic insect wing immersed in a specially devised turbulence tank were examined. Despite variation in aerodynamic forces generated between wing strokes, results show that the averaged force from flapping remains remarkably steady under turbulent conditions. Furthermore, measurements of the flows induced by the wing demonstrated that unsteady aerodynamic forces generated by flying insects actively buffer against external flow fluctuations. These results provide mechanistic evidence that insect flight is resilient to turbulent conditions, and establishes principles that aid in the development of insect-inspired robots tailored for flight in adverse flow environments.

History

Degree Type

Doctor of Philosophy

Department

Mechanical Engineering

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

Xinyan Deng

Additional Committee Member 2

George T. Chiu

Additional Committee Member 3

Jeffrey F. Rhoads

Additional Committee Member 4

Steve S. Yaninek

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