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Design of Minimally Actuated Legged Milli-Robots Using Compliant Mechanisms and Folding


This thesis explores milli- and meso-scale legged robot

design and fabrication with compliant mechanisms. Our approach

makes use of a process that integrates compliant flexure hinges

and rigid links to form parallel kinematic structures through the

folding of flat-fabricated sheets of articulated parts. Using

screw theory, we propose the formulation of an equivalent mechanism

compliance for a class of parallel mechanisms, and we use that

compliance to evaluate a scalar performance metric based on the

strain energy stored in a mechanism subjected to an arbitrary load.

Results from the model are supported by experimental measurements of a

representative mechanism. With the insight gained from the kinematic

mechanism design analysis, we propose and demonstrate compliant

designs for two six-legged robots comprising the robotic, autonomous,

crawling hexapod (RoACH) family of robots. RoACH is a two

degree of freedom, 2.4 gram, 3 cm long robot capable of untethered,

sustained, steerable locomotion. RoACH's successor, DynaRoach,

is 10 cm long, has one actuated degree of freedom and is capable of

running speeds of up to 1.4 m/s. DynaRoACH employs compliant legs

to help enable dynamic running and maneuvering and is three orders of

magnitude more efficient than its milli-scale predecessor. We experimentally

demonstrate the feasibility of a biologically-inspired approach to turning

control and dynamic maneuvering by adjusting leg stiffness. While the result

agrees qualitatively with predictions from existing reduced order models,

initial data suggest the full 3-dimensional dynamics play an important

role in six-legged turning.

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