Design of Minimally Actuated Legged Milli-Robots Using Compliant Mechanisms and Folding
- Author(s): Hoover, Aaron Murdock
- Advisor(s): Fearing, Ronald S.
- et al.
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.