RAISE: Spring & Wings: Resonance in insect and engineered flight with synchronous and stretch-activated actuation

本研究由跨学科科学与工程（RAISE）项目推进，将开发一个动力学模型，以加强对昆虫飞行作为一个综合系统的理解，并将这些信息应用于机器人设计。昆虫那么大的体型飞行是非常具有能量挑战性的。尽管如此，飞行的进化刺激了我们今天看到的昆虫的进化多样性。昆虫能飞很远的距离，能在拥挤和有风的环境中机动，还能以人类工程系统无法比拟的方式克服扑翼飞行的能量限制。昆虫将有弹性的外骨骼连接到翅膀上，以帮助在每个翅膀上储存和返回能量；然而，为了使能量回报最大化，昆虫必须以稳定的速度拍打翅膀。该项目将探索昆虫如何将弹簧和翅膀结合在一起，在一系列条件下管理能量需求和飞行控制。该项目还将探索昆虫用于飞行的两种不同类型的肌肉收缩如何在相同的潜在力学和肌肉特性下实现，从而为理解昆虫如何实现这种不同类型的飞行提供数学框架。该项目将使用带有弹性外骨骼和翅膀的机器人物理模型，以及昆虫级的拍打机器人来建立一个通用的“弹簧翼”框架。两家合作机构的研究将包括一个沉浸式的、垂直整合的本科研究项目。学生团队将在学年期间获得指导和现场研究经验，并将前往他们的交换地点进行跨学科的暑期研究。至少两名研究生和一名博士后也将接受跨学科培训。昆虫级的扑翼飞行需要高功率驱动和低延迟控制。为了减轻对飞行动力的需求，大多数昆虫通过肌肉来间接驱动翅膀，这些肌肉会使坚硬而有弹性的外骨骼变形。将弹性元件耦合到翅膀上，使昆虫有可能像一个共振系统一样运行，这将降低动力成本，但也会引入控制限制，例如限制翅拍频率调制。为了给拍动飞行提供动力，昆虫进化出了两种不同的驱动策略：同步飞行，由神经系统定时强迫拮抗肌肉，以及异步飞行，其中肌肉由于应变依赖性激活而建立自激振荡。该项目将建立弹簧翼系统的分析框架，测试昆虫是否在假设的谐振频率下工作，并开发一个动态缩放的机器人物理弹簧翼襟翼，以探索单个无量纲参数韦斯-福格数如何影响弹性能量储存和气动力控制。然后将这两种肌肉驱动策略结合起来，测试从异步昆虫进化而来的同步昆虫是否保留了自激（异步）振荡的必要生理特征。一个可以从两种稳定扑动状态转换的单一动力系统将在机器人物理系统和一个大规模的仿生扑翼机器人中进行测试。最后，将研究弹簧翼系统在共振处或远离共振处工作的权衡。该项目将生物和物理科学联系起来，将扩大对飞行中涉及的生理和生物力学原理和权衡的理解，并将通过应用于机器人技术来改变目前对昆虫飞行的理解。本科生和研究生以及一名博士后将参加导师指导的跨学科研究团队，并将在国家科学会议上展示研究成果。研究成果也将通过一个以生物为灵感的设计工作坊传播。该奖项由土木、机械和制造创新部门的动力学、控制和系统诊断项目、工程理事会以及生物科学理事会综合有机系统部门的生理机制和生物力学项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Research Advanced by Interdisciplinary Science and Engineering (RAISE) project will develop a dynamical model to enhance understanding of insect flight as an integrated system and apply this information to robotic design. Flight at the size of insects is very energetically challenging. Nonetheless, the evolution of flight spurred much of the evolutionary diversity of insects we see today. Insects fly long distances, maneuver in crowded and gusty environments, and overcome the energetic limitations of flapping wing flight in ways that cannot yet be matched in human-engineered systems. Insects couple springy exoskeletons to their wings to help store and return energy on every flap; however, to maximize energy return, insects would have to beat their wings at a steady rate. This project will explore how insects couple springs and wings together to manage energy requirements and flight control under a range of conditions. This project will also explore how the two distinct types of muscle contraction that insects use to power flight could both be achieved with the same underlying mechanics and muscle properties, enabling a mathematical framework for understanding how insects achieve such different types of flight. The project will use robophysical models with springy exoskeletons coupled to wings and insect-scale flapping robots to establish a general “spring-wing” framework. Research at both collaborating institutions will include an immersive, vertically integrated undergraduate research program. Student teams will receive mentorship and on-site research experience during the school year and will travel to their exchange location for interdisciplinary summer research. At least two graduate students and a post-doctoral fellow will also receive cross-disciplinary training.Insect-scale flapping-wing flight demands both high-power actuation and low-latency control. To mitigate flight power requirements, most insects actuate their wings indirectly via muscles that deform a stiff, elastic exoskeleton. Coupling elastic elements to the wings allows insects potentially to operate as a resonant system, which would reduce power costs but also would introduce control constraints, such as limiting wingbeat frequency modulation. To power flapping flight, insects evolved two distinct actuation strategies: synchronous flight, with time-periodic forcing of antagonistic muscles paced by the nervous system, and asynchronous flight, in which muscles set up self-excited oscillations due to strain-dependent activation. The project will establish an analytic framework for spring-wing systems, test if insects operate at their hypothesized resonant frequencies, and develop a dynamically scaled robophysical spring-wing flapper to explore how a single non-dimensional parameter, the Weis-Fogh number, influences elastic energy storage and aerodynamic force control. The two muscle actuation strategies will then be combined, testing if synchronous flying insects that have evolved from asynchronous insects retain the necessary physiological signatures of self-excited (asynchronous) oscillations. A single dynamic system that can transition from the two regimes of stable flapping will be tested in the robophysical system and in an at-scale, bio-inspired flapping wing robot. Finally, the tradeoffs of operating at or away from resonance in spring-wing systems will be investigated. The project bridges the biological and physical sciences, will expand understanding of physiological and biomechanical principles and trade-offs involved in flight, and should transform the current understanding of insect flight, with applications to robotics. Undergraduate and graduate students and a post-doctoral fellow will participate in mentored, interdisciplinary research teams, and will present research results at national scientific meetings. Research results will also be disseminated through a bio-inspired design workshop. This award is co-funded by the Dynamics, Control and Systems Diagnostics Program in the Division of Civil, Mechanical and Manufacturing Innovation, Directorate for Engineering, and the Physiological Mechanisms and Biomechanics Program in the Division of Integrative Organismal Systems, Directorate for Biological Sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.