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Goldman, Daniel I.

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Author: Goldman, Daniel I. × End date: 2008 × Start date: 2008 × search.filters.applied.f.isOrgUnitOfPublicationTitle: College of Sciences ×

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    Integrating a Hierarchy of Simulation Tools for Legged Robot Locomotion
    (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.
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    Scaling and Dynamics of Sphere and Disk Impact into Granular Media
    (Georgia Institute of Technology, 2008-02-29) Goldman, Daniel I. ; Umbanhowar, Paul B.
    Direct measurements of the acceleration of spheres and disks impacting granular media reveal simple power law scalings along with complex dynamics which bear the signatures of both fluid and solid behavior. The penetration depth scales linearly with impact velocity while the collision duration is constant for sufficiently large impact velocity. Both quantities exhibit power law dependence on sphere diameter and density, and gravitational acceleration. The acceleration during impact is characterized by two jumps: a rapid, velocity-dependent increase upon initial contact and a similarly sharp depth-dependent decrease as the impacting object comes to rest. Examination of the measured forces on the sphere in the vicinity of these features leads to an experimentally based granular force model for collision. We discuss our findings in the context of recently proposed phenomenological models that capture qualitative dynamical features of impact but fail both quantitatively and in their inability to capture significant acceleration fluctuations that occur during penetration and which depend on the impacted material.
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    Design of a Bio-inspired Dynamical Vertical Climbing Robot
    (Georgia Institute of Technology, 2008) Clark, Jonathan E. ; Goldman, Daniel I. ; Lin, Pei-Chun ; Lynch, Goran ; Chen, Tao S. ; Komsuoglu, Haldun ; Full, Robert J. ; Koditschek, Daniel E.
    This paper reviews a template for dynamical climbing originating in biology, explores its stability properties in a numerical model, and presents emperical data from a physical prototype as evidence of the feasibility of adapting the dynamics of the template to robot that runs vertically upward. The recently proposed pendulous climbing model abstracts remarkable similarities in dynamic wall scaling behavior exhibited by radically different animal species. The present paper’s first contribution summarizes a numerical study of this model to hypothesize that these animals’ apparently wasteful commitments to lateral oscillations may be justified by a significant gain in the dynamical stability and, hence, the robustness of their resulting climbing capability. The paper’s second contribution documents the design and offers preliminary empirical data arising from a physical instantiation of this model. Notwithstanding the substantial differences between the proposed bio-inspired template and this physical manifestation, initial data suggest the mechanical climber may be capable of reproducing both the motions and ground reaction forces characteristic of dynamical climbing animals. Even without proper tuning, the robot’s steady state trajectories manifest a substantial exchange of kinetic and potential energy, resulting in vertical speeds of 0.30 m/s (0.75 bl/s) and claiming its place as the first bio-inspired dynamical legged climbing platform.