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Dynamic Characterization of a Grasshopper-Inspired Gliding and Deployable Wing for Efficient Multi-Modal Locomotion

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Nature's Inspiration

Many of the current flying insect-scale robots utilize a single mode of locomotion. At this scale, multi-modal locomotion is limited since each mode of locomotion requires supplemental devices and additional actuators, which is challenging given the volume, power, and size constraints. Compared to the current insect-scale robots, grasshoppers are excellent examples of a system displaying energy-efficient flight and multi-modal locomotion. Grasshoppers can crawl, jump, flap and glide. Unlike most insects, which rely primarily on flapping, grasshoppers demonstrate energy-efficient flight through gliding. Grasshoppers are one of the few insects that currently use gliding as a considerable part of their flight. They flap to gain velocity and perform intricate movements while they glide to save energy and travel long distances. In addition to multiple locomotion modes, grasshoppers can inspire micro-scale robots in terms of their transition dynamics from terrestrial to aerial locomotion. The transition from terrestrial to aerial locomotion is initiated with a jump. The wings are folded close to the body during the jump to reduce drag and maximize jump height. As the grasshopper is launched from ground to air, the grasshoppers' fore and hind wings unfold to generate aerodynamic forces. Grasshoppers have evolved a wing deployment mechanism as an adaption for multi-modal locomotion. Thus, the grasshoppers' gliding flight and deployable wing mechanism are outstanding inspirations for current insect-scale robotic applications, especially for those performing multiple modes of locomotion.

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Collected Grasshoppers for Inspiration

BAM Approach and Recent Results

This research project centers on the development of an insect-scale glider inspired by grasshoppers. Its primary aim is to unravel the intricacies of grasshoppers' jump-glide transition locomotion, with a particular focus on potential applications in insect-scale robotics. The research unfolds in several phases, commencing with an in-depth characterization of the wing morphology of grasshoppers. Notably, the hindwings, constituting approximately 70 of total lift production, become the focal point for measurement. These comprehensive morphological measurements lay the foundation for the ensuing stages of the research. Building upon this understanding, the study proceeds with a thorough examination of the aerodynamics of grasshopper-inspired wing models. Using flat plate models resembling the planforms observed in grasshoppers, a wind tunnel experiment is conducted, sweeping the angle of attack from 0 to 30 degrees in 3-degree increments at a Reynolds number of 3750, the range at which grasshoppers fly. The outcomes reveal the aerodynamic forces, with lift and drag coefficients, where the lift-to-drag ratio ranges from 1.6 to 3.8.

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Wind Tunnel Aerodynamic Characterization

Subsequently, the research advances into the realm of free-flight experiments, with the creation of a glider closely mirroring the hindwing morphology of Schistocerca americana grasshoppers. The initial design employs flat plates, which, disappointingly, fail to generate the anticipated amount of lift. This leads to a redesign incorporating an ESA reflexed camber airfoil, resulting in an improved lift-to-drag ratio ranging from 3.5 to 4.2.

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Grasshopper Inspired Glider for Free Flight Aerodynamic Characterization

While this is a significant enhancement, it falls within the lower end of the grasshoppers' aerodynamic performance range. The research delves deeper into the wing structures of grasshoppers, particularly the intriguing corrugations found in their wings. These corrugations are renowned for their pivotal role in insect aerodynamics. As a result, our current research focuses on the inclusion of these wing corrugations in the glider design for future research endeavors.

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Comparison to Grasshopper

Engineering Impact

The research stands to make impact on the engineering landscape by pushing the boundaries of insect-scale robotics. By drawing inspiration from the gliding behavior of grasshoppers, it offers a promising path toward creating more versatile and energy-efficient robotic systems. These advancements are particularly relevant for applications where small, agile, and autonomous robots are needed, such as in surveillance missions or environmental monitoring in challenging terrains. The notion of untethered operation is a particularly compelling prospect, as it could potentially eliminate the need for frequent recharging or complex power tethering systems. Furthermore, the focus on incorporating biologically inspired features, such as wing corrugations and complex wing profiles, underscores the potential for entirely new paradigms in bio-inspired engineering, opening doors to innovative solutions to a wide array of engineering challenges across various industries.

Acknowledgments

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