Burden, SamSullivan, Joseph Garrett2025-08-012025-08-012025-08-012025Sullivan_washington_0250E_28597.pdfhttps://hdl.handle.net/1773/53566Thesis (Ph.D.)--University of Washington, 2025This dissertation explores the potential of Handed Shearing Auxetic (HSA) structures ascomponents in energy-efficient robotic actuators. We present a novel parallel elastic actuator that integrates an HSA with a quasi-direct drive motor, combining passive compliance and static braking in a compact and mechanically efficient design. To characterize the actuator’s nonlinear viscoelastic behavior, we develop a structured modeling framework grounded in Lagrangian mechanics, using convex elastic and dissipation potentials. A variational loss based on the Euler–Lagrange residual enables tractable system identification from trajectory data using only motor telemetry. We validate this approach on a vertically hopping monopod robot, where the learned models are integrated into a trajectory optimization framework. Experiments demonstrate improved electrical efficiency during hopping and load-bearing tasks, particularly under op- timized control. These results suggest that HSAs can contribute meaningfully to compliant actuation and motivate further research into their use in more general legged locomotion systems.application/pdfen-USCC BYActuatorAuxeticCompliantHoppingRobotViscoelasticRoboticsMechanicsMaterials ScienceElectrical and computer engineeringThesis