Reliable systems for micro aerial vehicles -- Design approach
Editor's Note: Embedded designers must contend with a host of challenges in creating systems for harsh environments. Harsh environments present unique characteristics not only in terms of temperature extremes but also in areas including availability, security, very limited power budget, and more. In Rugged Embedded Systems, the authors present a series of papers by experts in each of the areas that can present unusually demanding requirements. A separate excerpt of the book addresses fundamental concerns in reliability and system resiliency.
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Adapted from Rugged Embedded Systems, Computing in Harsh Environments, by Augusto Vega. Pradip Bose, Alper Buyuktosunoglu.
CHAPTER 7. Reliable electrical systems for micro aerial vehicles and insect-scale robots: Challenges and progress (Cont.)
By X. Zhang, Washington University, St. Louis, MO, United States
3 OVERVIEW OF RoboBee
3.1 MOTIVATED BY A GLOBAL CRISIS
Our intrepid pursuit to build an insect-scale aerial robot is driven with a mission to address a global crisis—the decline of pollinator populations in nature. Bees and other animal pollinators are responsible for the pollination of 60–80% of the world’s flowering plants and 35% of crop production, and hence the continuing decline could cost the global economy more than 200 billion dollars and spell devastating effect on human nutrition that is beyond the measure of monetary values. To these days, the exact cause of the decline remains to be determined, but its disastrous consequence calls for awareness and actions.
While the near-term remedy to this problem will certainly have to come out of the toolbox of entomologists, ecologists, and environmental scientists, as engineers and technologists, we would like to approach it with a longer-term out-of-the-box proposal by looking at the feasibility of building artificial robotic pollinators at the insect scale. We consider it a moonshot idea whose merits lie mostly in the creativity it spurs and the discovery it enables rather than its immediate practicality. It is against this backdrop that we, a team of investigators from Harvard University’s John A. Paulson School of Engineering and Applied Sciences and Department of Organismic and Evolutionary Biology and Northeastern University’s Department of Biology, conceived the project of RoboBee.
3.2 INSPIRED BY NATURE
It is no coincidence that we look to nature for inspiration to build tiny autonomous flying apparatus. As we mentioned earlier in the chapter, larger-scale man-made aerial vehicles can take advantage of passive stability that is associated with a large Reynolds number, whereas smaller-sized MAVs commonly employ unsteady mechanisms such as wing flapping to sustain flight. Insects are among the most agile flying creatures on Earth, and we probably have all experienced this first hand at failed attempts to swat an evasively maneuvering fly or mosquito.
Since no existing vehicles have been demonstrated before to achieve comparable maneuverability at the insect scale, we modeled the form and functionality of RoboBee directly after the morphology of Diptera (flies), because Dipteran flight has been well-studied and documented in the past .
3.3 BASIC DESIGN AND IMPLEMENTATION
RoboBee requires mechanical components with feature sizes between micrometers and centimeters that fall between the gap of conventional machining and assembly methods and MEMS fabrication. To tackle this problem, the mechanical experts on our team developed a design and manufacturing methodology called “smart composite microstructure” (SCM), which stacks different material layers together with adhesives and applies laser-micromachining and lamination to bring them into desired shape. We are able to employ this monolithic planar process to manufacture all the electromechanical elements of the robotic fly, including flight muscles, thorax, skeleton, and wings. High stiffness-to-weight-ratio carbon fiber-reinforced composites are used for the structural elements, while polyimide film flexure hinges are used for articulation to emulate low-friction revolute joints.