Komsuoglu, Haldun
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Publication Integrating a Hierarchy of Simulation Tools for Legged Robot Locomotion(2008-09-01) Slatton, Andrew; Ding, Yang; Umbanhowar, P B; Goldman, Daniel; Haynes, Galen C; Komsuoglu, Haldun; Koditschek, Daniel E; Cohen, DanielWe 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.Publication Dynamic Legged Mobility---an Overview(2009-05-20) Komsuoglu, HaldunAbility to translate to a goal position under the constrains imposed by complex environmental conditions is a key capability for biological and artificial systems alike. Over billions of years evolutionary processes have developed a wide range of solutions to address mobility needs in air, in water and on land. The efficacy of such biological locomotors is beyond the capabilities of engineering solutions that has been produced to this date. Nature has been and will surely remain to be a source of inspiration for engineers in their quest to bring "real mobility" to their creations. In recent years a new class of dynamic legged terrestrial robotic systems \cite{Autumn-Buehler-Cutkosky.SPIE2005,Raibert.Book1986,Raibert-Blankesport-Nelson.IFAC2008,Saranli-Buehler-Koditschek.IJRR2001} have been developed inspired by, but without mimicking, the examples from the Nature. The experimental work with these platforms over the past decade has led to an improved appreciation of legged locomotion. This paper is an overview of fundamental advantages dynamic legged locomotion offers over the classical wheeled and tracked approaches.Publication Sensitive dependence of the motion of a legged robot on granular media(2009-02-09) Li, Chen; Umbanhowar, P B; Komsuoglu, Haldun; Koditschek, Daniel E; Goldman, DanielLegged locomotion on flowing ground (e.g., granular media) is unlike locomotion on hard ground because feet experience both solid- and fluid-like forces during surface penetration. Recent bioinspired legged robots display speed relative to body size on hard ground comparable with high-performing organisms like cockroaches but suffer significant performance loss on flowing materials like sand. In laboratory experiments, we study the performance (speed) of a small (2.3 kg) 6-legged robot, SandBot, as it runs on a bed of granular media (1-mm poppy seeds). For an alternating tripod gait on the granular bed, standard gait control parameters achieve speeds at best 2 orders of magnitude smaller than the 2 body lengths/s (≈60 cm/s) for motion on hard ground. However, empirical adjustment of these control parameters away from the hard ground settings restores good performance, yielding top speeds of 30 cm/s. Robot speed depends sensitively on the packing fraction φ and the limb frequency ω, and a dramatic transition from rotary walking to slow swimming occurs when φ becomes small enough and/or ω large enough. We propose a kinematic model of the rotary walking mode based on generic features of penetration and slip of a curved limb in granular media. The model captures the dependence of robot speed on limb frequency and the transition between walking and swimming modes but highlights the need for a deeper understanding of the physics of granular media.Publication March of the Sandbots(2009-04-01) Komsuoglu, Haldun; Goldman, Daniel; Koditschek, Daniel EGoldman at Georgia Tech, Koditschek and Komsuoglu at the University of Pennsylvania, in Philadelphia, and other collaborators - are hoping that by studying the zebra-tailed lizard and a menagerie of other desert-dwelling creatures, we can create more agile versions of their six-legged robot, SandBot.Publication Design of a Bio-Inspired Dynamical Vertical Climbing Robot(2007-01-01) Clark, Jonathan E; Goldman, Daniel I; Lin, Pei-Chun; Lynch, Goran; Komsuoglu, Haldun; Chen, Tao S; Full, Robert J; Koditschek, Daniel EThis paper reviews a template for dynamical climbing originating in biology, explores its stability properties in a numerical model, and presents empirical 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.Publication Classification and Identification of Environment Through Dynamic Coupling(2010-07-15) Komsuoglu, HaldunThis paper presents a methodology enabling robotic systems to classify and identify their environment according to the mechanical properties of the local contact dynamics. Described approach employs existing proprioceptive sensors and requires no additional specialized hardware. Identification process is performed in real-time with temporal resolution of measurement updates determined by the periodicity of the limit behavior. While the basic concept has a wide application spectrum, our discussion focuses on terrestrial locomotion where contact properties, such a compliance, damping, sheer friction and surface topology, are important environmental markers. Accurate identification of environmental parameters enables two types of applications. In behavioral control, availability of measurements on environmental parameterization can facilitate better adaptation of actuation strategy. In localization and map building applications, such mechanical characteristics of the environment, which are typically hard to attain, can serve as a new set of classifiers. Presented approach is founded on the observation that locomotive behaviors, and particularly the dynamic ones, emerge from the interaction between the active actuation actions of the mechanism with its environment. To evaluate our concept in a systematic fashion we constructed a simplified numerical model of a dynamic hexapod robot. We present results on numerical simulations and outline a path for a physical implementation on dynamic hexapod robot.Publication The Role of Reflexes Versus Central Pattern Generators(2002-01-01) Komsuoglu, Haldun; Klavins, Eric; Koditschek, Daniel E; Full, Robert JAnimals execute locomotor behaviors and more with ease. They have evolved these breath-taking abilities over millions of years. Cheetahs can run, dolphins can swim and flies can fly like no artificial technology can. It is often argued that if human technology could mimic nature, then biological-like performance would follow. Unfortunately, the blind copying or mimicking of a part of nature [Ritzmann et al., 2000] does not often lead to the best design for a variety of reasons [Vogel, 1998]. Evolution works on the "just good enough" principle. Optimal designs are not the necessary end product of evolution. Multiple satisfactory solutions can result in similar performances. Animals do bring to our attention amazing designs, but these designs carry with them the baggage of their history. Moreover, natural design is constrained by factors that may have no relationship to human engineered designs. Animals must be able to grow over time, but still function along the way. Finally, animals are complex and their parts serve multiple functions, not simply the one we happen to examine. In short, in their daunting complexity and integrated function, understanding animal behaviors remains as intractable as their capabilities are tantalizing.Publication A Physical Model for Dynamical Arthropod Running on Level Ground(2008-05-30) Komsuoglu, Haldun; Sohn, Kiwon; Full, Robert J; Koditschek, Daniel EArthropods with their extraordinary locomotive capabilities have inspired roboticists, giving rise to major accomplishments in robotics research over the past decade. Most notably bio-inspired hexapod robots using only task level open-loop controllers [22, 9] exhibit stable dynamic locomotion over highly broken and unstable terrain. We present experimental data on the dynamics of Sprawl- Hex — a hexapod robot with adjustable body sprawl — consisting of time trajectory of full body configuration and single leg ground reaction forces. The dynamics of SprawlHex is compared and contrasted to that of insects. SprawlHex dynamics has qualitative similarities to that of insects in both sagittal and horizontal plane. SprawlHex presents a step towards construction of an effective physical model to study arthropod locomotion.