Dissertation Defense

Advances in Feedback Control for High-dimensional Bipedal Models

Omar Harib

Bipedal machines bring with them the promise of advancements in both work and personal sectors. These machines are meant to exhibit diverse gaits, many designed with agility in mind. To take full advantage their mechanical capabilities require advanced optimization and feedback design methods, which are the central theme of this dissertation.

Our specific hardware targets are (1) an exoskeleton designed by Wandercraft that allows people with paraplegia to walk again without the use of crutches, and (2) a Cassie-series agile bipedal.

The first topic addressed is a toolset called C-FROST, which allows FROST to generate stand-alone, C++ based, executables for running optimizations allowing for parallelization and easy deployment to the cloud.

The second topic is gait and feedback control design for the Wandercraft exoskeleton. Feedback controllers are for the exoskeleton use Hybrid Zero Dynamics (HZD), Gait Libraries, and an extension of HZD called Generalized Hybrid Zero Dynamics (G-HZD).

Work on the exoskeleton revealed a fundamental drawback in the existing G-HZD approach, which motivated the third main topic of the dissertation. In G-HZD, the manifold is built from trajectories that arise from a boundary-value problem, and thus specifying the proper boundary of the manifold is crucial to the success of the method.

This dissertation proposes a novel method for the design of the boundary manifold. In this dissertation, the new approach is demonstrated on an inverted pendulum on a cart and compared to the original approach.

Then, we demonstrate how to implement the new approach on Cassie with experimental results included.

Chair: Professor Jessy Grizzle