Dynamic Humanoid Locomotion: A Scalable Formulation for HZD Gait Optimization
Publication Type:
Journal
Authors:
Co-Authors:
Ayonga Hereid, Eric A. Cousineau, and Aaron D. Ames
Year Published:
2018
Abstract:
Hybrid zero dynamics (HZD) has emerged as a popular
framework for dynamic walking but has significant implementation
difficulties when applied to the high degrees of freedom
humanoids. The primary impediment is the process of gait design—
it is difficult for optimizers to converge on a viable set of virtual
constraints defining a gait. This paper presents a methodology that
allows for fast and reliable generation of dynamic robotic walking
gaits through the HZD framework, even in the presence of underactuation.
Specifically, we describe an optimization formulation
that builds upon the novel combination of HZD and direct collocation
methods. Furthermore, achieving a scalable implementation
required developing a defect-variable substitution formulation to
simplify expressions, which ultimately allows us to generate compact
analytic Jacobians of the constraints. We experimentally validate
our methodology on an underactuated humanoid, DURUS,
a spring-legged machine designed to facilitate energy-economical
walking. We show that the optimization approach, in concert with
the HZD framework, yields dynamic and stable walking gaits in
hardware with a total electrical cost of transport of 1.33.
Journal:
IEEE Transactions on Robotics
Volume:
34
Issue:
2
Pagination:
ISSN:
Short Title:
Date Published:
1/17/2018