(Georgia Institute of Technology, 2010-04-22)
Li, Chen; Umbanhowar, Paul B.; Komsuoglu, | Haldun; Goldman, Daniel I.
Achieving effective locomotion on diverse terrestrial substrates can require subtle changes of limb kinematics. Biologically inspired legged robots (physical models of organisms) have shown impressive mobility on hard ground but suffer performance loss on unconsolidated granular materials like sand. Because comprehensive limb- ground interaction models are lacking, optimal gaits on complex yielding terrain have been determined empirically. To develop predictive models for legged devices and to provide hypotheses for biological locomotors, we systematically study the performance of SandBot, a small legged robot, on granular media as a function of gait parameters. High performance occurs only in a small region of parameter space. A previously introduced kinematic model of the robot combined with a new anisotropic granular penetration force law predicts the speed. Performance on granular media is maximized when gait parameters minimize body acceleration and limb interference, and utilize solidification features of granular media.
(Georgia Institute of Technology, 2008-09)
Slatton, Andrew; Cohen, Daniel; Ding, Yang; Umbanhowar, Paul B.; Goldman, Daniel I.; Haynes, G. Clark; Komsuoglu, Haldun; Koditschek, Daniel E.
We are interested in the development of a variety
of legged robot platforms intended for operation in
unstructured outdoor terrain. In such settings, the traditions of
rational engineering design, driven by analytically informed and
computationally assisted studies of robot-environment models,
remain ineffective due to the complexity of both the robot
designs and the terrain in which they must operate. Instead,
empirical trial and error often drives the necessary incremental
and iterative design process, hence the development of such
robots remains expensive both in time and cost, and is often
closely dependent upon the substrate properties of the locomotion
terrain. This paper describes a series of concurrent but
increasingly coordinated software development efforts that aim
to diminish the gap between easily interfaced and physically
sound computational models of a real robot’s operation in a
complex natural environment. We describe a robot simulation
environment in which simple robot modifications can be easily
prototyped along and “played” into phenomenological models
of contact mechanics. We particularly focus on the daunting
but practically compelling example of robot feet interacting
granular media, such as gravel or sand, offering a brief report
of our progress in deriving and importing physically accurate
but computationally tractable phenomenological substrate models
into the robot execution simulation environment. With a
goal of integration for future robot prototyping simulations,
we review the prospects for diminishing the gap between the
integrated computational models and the needs of physical
platform development.