1 Flying Insects as Model Animals of Robotics
Flying insects have attracted a number of scientists for many years, and their contributions to biological sciences should never be underestimated: Research on flying insects has spread out into almost all fields, including sociology, genetics, evolutionary biology, neuroscience, and the other behavioral sciences. What I have found most fascinating about flying insects is their remarkable intelligence despite their small sizes of body and nervous structures. Flying insects live and survive almost everywhere on the planet; they are capable of wide-ranging behavioral capabilities, including basic behaviors such as takeoff, landing, escaping, chasing, and mating, as well as foraging and learning; and some species can even communicate to form social structures. While human beings exhibit similar behaviors, flying insects achieve these functions by using typically very different mechanisms from those of humans, and they are often very elegant. I don't remember how many times I was surprised by the clever solutions by which animals achieve these functionalities.
Owing to the enormous amount of accumulated knowledge and the many investigations of them in biology, flying insects have also become one of the most representative model animals in engineering sciences. Previously, the visual systems of flying insects were studied intensively and incorporated into the important literature on computer vision [1, 2]. Also, flying insects were investigated as interesting case studies of mechanics, in which they revealed a number of mechanical design principles of nature [3, 4]. In robotics research, a number of interdisciplinary collaborations between engineers and biologists have successfully identified mechanisms of adaptive behaviors by sensory-motor pathways of insects .
From what I have observed in its recent development, the research field of flying insects seems to be entering a new era based on the availability of new technologies. For behavioral studies of animals, we now have easier access to various imaging and computational devices, which facilitate more comprehensive experiments and analysis to uncover the mysteries of physiological processes and aerodynamic interactions in animals' adaptive behaviors. The rapid progress of tool availability is more prominent in robotics research: Micromanufacturing techniques as well as small-sized sensors, motors, processors, and batteries, for example, make it possible to realize remarkable robotic systems that are as small and agile as biological systems. The book Flying Insects and Robots was published at the very time when the new era of this research field had just started.
The book contains 21 chapters authored by prominent experts in this rapidly growing field. Unlike similar books of this kind, which often focus exclusively on one topic, this volume covers almost all the highly active research topics investigated in the last years.
The contents of this book can be roughly divided into two parts.
The first half introduces the recent development of studies of sensory-motor processes in flying insects and robots. Unlike conventional robots, which typically rely on non-visual sensory information (e.g., gyros, GPS, laser range finders, and radars), vision plays a central role in the insects' flight control. The first part of this book provides the mechanisms of vision-based flight control in nature and the engineers' efforts to conceptualize these mechanisms and incorporate them into artificial systems. More specifically, this part introduces in detail the following topics on vision-based flight control.
After the introductory chapter on the fundamentals of biomechanics and physiological studies of flying insects (Chapter 1), it is carefully explained how optic flow is used in flying insects (Chapters 2, 3, 6, 7, and 9). A set of more challenging problems of visuomotor pathways in the insects are also nicely summarized in this part. Namely, Chapter 4 introduces how active vision of flying insects can be studied; Chapter 5 focuses on the influence of wide-field integration in visuomotor control; and Chapter 7 introduces the recent model-based studies of insects' visual navigation.
Compared to other such books, a unique aspect of this one lies in the fact that almost all chapters explain how the biological studies have led to engineering contributions. For example, Chapters 2 and 3 introduce how the biological studies on optic flow resulted in robust speed control and obstacle avoidance of aerial vehicles, and Chapter 9 explains how the basic principles of visual odometry can be engineered and integrated into a robotic system. Chapters 8 and 10 suggest how the cutting-edge small-scale manufacturing techniques could be employed to reproduce biomimetic visual sensory systems.
The second topic area of this book is the flight mechanisms of small-sized flying robots. Throughout 11 chapters (Chapters 11–21), this book documents the engineers' ceaseless challenges in designing animal-like flying robots. More specifically, Chapters 11 and 12 explain the underlying aerodynamics of both flapping and fixed wings for micro aerial vehicles (MAVs), and Chapters 13 and 14 introduce the challenges of flapping wing designs that exploit passive dynamics. The design issues are then extended to the whole body in Chapters 15, 16, 18, and 19, which discuss how motors and other components could be integrated into small body structures to achieve many motor functions (including flying, jumping, and walking). Chapter 17 covers the fundamentals of motion control in flying insects. And the last two chapters introduce the important technological challenges to solar-powered MAVs (Chapter 20) and microfabrication techniques (Chapter 21).
Because MAVs are severely constrained by body size, body weight, actuation power, energy storage, and computational resources, the development of these robots is highly challenging. The highlight of this book, at least from my perspective, is the ways researchers learn abstract design principles from nature and incorporate them into functional organisms. Such understanding-by-building approaches can be best represented, for example, by the discovery of mechanically self-stabilizing passive mechanisms (e.g., Chapters 13 and 15) and minimalistic control architectures (Chapters 17, 18, and 19).
3 Different Ways to Enjoy the Ongoing Interdisciplinary Research
Because this book introduces the active research areas and the current technical challenges one by one in great detail, each chapter is self-contained and there is relatively small coherence between chapters. For example, the issue of optic flow is explained from different perspectives in five or six chapters, and many design challenges of micro aerial vehicles are also introduced in five or six different chapters. Thus, for those who expect comprehensive introductory lessons, it will be difficult to grasp the big picture from this book. This volume is not a textbook for non-experts that explains an established discipline systematically and concisely, but is intended to provide an overview of ongoing research projects. For this reason, it might be helpful to go through some complementary materials (e.g., [6, 7]) along with this book, which provide some underlying guiding principles of bio-inspired robotics.
It is also important to mention that this volume has several faces. For biologists, it should be interesting to see the collections of success stories in which biological studies and findings were transferred to engineering sciences and applications; researchers in microfabrication and/or unconventional materials will find a number of challenges and applications that they could contribute to; and scientists in computer engineering and optics will obtain additional insights into the nature of sensory-motor processes. All in all, because of its interdisciplinary character, it should not be difficult for most scientists to find a way to enjoy this book.
In general, the book contains an excellent up-to-date collection of research projects in flying insects and robots. The recent achievements and challenges are introduced by the leading scientists of the field, and each chapter is self-contained, which may be highly beneficial for those who are interested in specific areas of research. The target audience should be both engineering and biological scientists, including mechanical, electrical, and computational engineering as well as artificial life/intelligence, neuroscience, and other behavioral sciences. I would also recommend the use of this book in advanced courses of graduate studies.
Bio-Inspired Robotics Laboratory, Institute of Robotics and Intelligent Systems, ETH Zurich, LEO-D 9.2, Leonhardstrasse 27, CH-8092 Zurich, Switzerland. E-mail: firstname.lastname@example.org