The Experts below are selected from a list of 53028 Experts worldwide ranked by ideXlab platform
Claire J Tomlin - One of the best experts on this subject based on the ideXlab platform.
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decentralized overlapping control of a formation of unmanned aerial vehicles
Automatica, 2004Co-Authors: Dusan M. Stipanovic, R. Teo, Gokhan Inalhan, Claire J TomlinAbstract:Decentralized overlapping feedback laws are designed for a formation of unmanned aerial vehicles. The dynamic model of the formation with an information structure constraint in which each vehicle, except the leader, only detects the vehicle directly in front of it, is treated as an interconnected system with overlapping subsystems. Using the mathematical framework of the inclusion principle, the interconnected system is expanded into a Higher Dimensional Space in which the subsystems appear to be disjoint. Then, at each subsystem, a static state feedback controller is designed to robustly stabilize the perturbed nominal dynamics of the subsystem. The design procedure is based on the application of convex optimization tools involving linear matrix inequalities. As a final step, the decentralized controllers are contracted back to the original interconnected system for implementation.
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Decentralized overlapping control of a formation of unmanned aerial vehicles
Proceedings of the 41st IEEE Conference on Decision and Control 2002., 2002Co-Authors: Dusan M. Stipanovic, R. Teo, Gokhan Inalhan, Claire J TomlinAbstract:Decentralized overlapping feedback laws are designed for a formation of unmanned aerial vehicles. The dynamic model of the formation with an overlapping information structure constraint is treated as an interconnected system with overlapping subsystems. Using the mathematical framework of the inclusion principle, the interconnected system is expanded into a Higher Dimensional Space in which the subsystems appear to be disjoint. On a subsystem level, a static state feedback controller is designed to robustly stabilize the perturbed nominal dynamics of the subsystem. The design procedure is based on the hierarchical application of convex optimization tools involving linear matrix inequalities. As a final step, the decentralized controllers are contracted back to the original interconnected system for implementation.
Ming Cao - One of the best experts on this subject based on the ideXlab platform.
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singularity free guiding vector field for robot navigation
IEEE Transactions on Robotics, 2021Co-Authors: Weijia Yao, Hector Garcia De Marina, Bohuan Lin, Ming CaoAbstract:In robot navigation tasks, such as unmanned aerial vehicle (UAV) highway traffic monitoring, it is important for a mobile robot to follow a specified desired path. However, most of the existing path-following navigation algorithms cannot guarantee global convergence to desired paths or enable following self-intersected desired paths due to the existence of singular points where navigation algorithms return unreliable or even no solutions. One typical example arises in vector-field guided path-following (VF-PF) navigation algorithms. These algorithms are based on a vector field, and the singular points are exactly where the vector field diminishes. Conventional VF-PF algorithms generate a vector field of the same dimensions as those of the Space where the desired path lives. In this article, we show that it is mathematically impossible for conventional VF-PF algorithms to achieve global convergence to desired paths that are self-intersected or even just simple closed (precisely, homeomorphic to the unit circle). Motivated by this new impossibility result, we propose a novel method to transform self-intersected or simple closed desired paths to nonself-intersected and unbounded (precisely, homeomorphic to the real line) counterparts in a Higher Dimensional Space. Corresponding to this new desired path, we construct a singularity-free guiding vector field on a Higher Dimensional Space. The integral curves of this new guiding vector field is thus exploited to enable global convergence to the Higher Dimensional desired path, and therefore the projection of the integral curves on a lower Dimensional subSpace converge to the physical (lower Dimensional) desired path. Rigorous theoretical analysis is carried out for the theoretical results using dynamical systems theory. In addition, we show both by theoretical analysis and numerical simulations that our proposed method is an extension combining conventional VF-PF algorithms and trajectory tracking algorithms. Finally, to show the practical value of our proposed approach for complex engineering systems, we conduct outdoor experiments with a fixed-wing airplane in windy environment to follow both 2-D and 3-D desired paths.
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singularity free guiding vector field for robot navigation
arXiv: Robotics, 2020Co-Authors: Weijia Yao, Hector Garcia De Marina, Bohuan Lin, Ming CaoAbstract:Most of the existing path-following navigation algorithms cannot guarantee global convergence to desired paths or enable following self-intersected desired paths due to the existence of singular points where navigation algorithms return unreliable or even no solutions. One typical example arises in vector-field guided path-following (VF-PF) navigation algorithms. These algorithms are based on a vector field, and the singular points are exactly where the vector field diminishes. In this paper, we show that it is mathematically impossible for conventional VF-PF algorithms to achieve global convergence to desired paths that are self-intersected or even just simple closed (precisely, homeomorphic to the unit circle). Motivated by this new impossibility result, we propose a novel method to transform self-intersected or simple closed desired paths to non-self-intersected and unbounded (precisely, homeomorphic to the real line) counterparts in a Higher-Dimensional Space. Corresponding to this new desired path, we construct a singularity-free guiding vector field on a Higher-Dimensional Space. The integral curves of this new guiding vector field is thus exploited to enable global convergence to the Higher-Dimensional desired path, and therefore the projection of the integral curves on a lower-Dimensional subSpace converge to the physical (lower-Dimensional) desired path. Rigorous theoretical analysis is carried out for the theoretical results using dynamical systems theory. In addition, we show both by theoretical analysis and numerical simulations that our proposed method is an extension combining conventional VF-PF algorithms and trajectory tracking algorithms. Finally, to show the practical value of our proposed approach for complex engineering systems, we conduct outdoor experiments with a fixed-wing airplane in windy environment to follow both 2D and 3D desired paths.
Gia Dvali - One of the best experts on this subject based on the ideXlab platform.
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phenomenology astrophysics and cosmology of theories with submillimeter dimensions and tev scale quantum gravity
Physical Review D, 1999Co-Authors: Nima Arkanihamed, Savas Dimopoulos, Gia DvaliAbstract:We recently proposed a solution to the hierarchy problem not relying on low-energy supersymmetry or technicolor. Instead, the problem is nullified by bringing quantum gravity down to the TeV scale. This is accomplished by the presence of $ng~2$ new dimensions of submillimeter size, with the SM fields localized on a 3-brane in the Higher Dimensional Space. In this paper we systematically study the experimental viability of this scenario. Constraints arise both from strong quantum gravitational effects at the TeV scale, and more importantly from the production of massless Higher Dimensional gravitons with TeV suppressed couplings. Theories with $ng2$ are safe due mainly to the infrared softness of Higher Dimensional gravity. For $n=2,$ the six Dimensional Planck scale must be pushed above $\ensuremath{\sim}30\mathrm{TeV}$ to avoid cooling SN 1987A and distortions of the diffuse photon background. Nevertheless, the particular implementation of our framework within type I string theory can evade all constraints, for any $ng~2,$ with string scale ${m}_{s}\ensuremath{\sim}1\mathrm{TeV}.$ We also explore novel phenomena resulting from the existence of new states propagating in the Higher Dimensional Space. The Peccei-Quinn solution to the strong $\mathrm{CP}$ problem is revived with a weak scale axion in the bulk. Gauge fields in the bulk can mediate repulsive forces $\ensuremath{\sim}{10}^{6}--{10}^{8}$ times stronger than gravity at submillimeter distances, as well as help stabilize the proton. Higher-Dimensional gravitons produced on our brane and captured on a different ``fat'' brane can provide a natural dark matter candidate.
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phenomenology astrophysics and cosmology of theories with submillimeter dimensions and tev scale quantum gravity
Physical Review D, 1999Co-Authors: Nima Arkanihamed, Savas Dimopoulos, Gia DvaliAbstract:We recently proposed a solution to the hierarchy problem not relying on low-energy supersymmetry or technicolor. Instead, the problem is nullified by bringing quantum gravity down to the TeV scale. This is accomplished by the presence of n{ge}2 new dimensions of submillimeter size, with the SM fields localized on a 3-brane in the Higher Dimensional Space. In this paper we systematically study the experimental viability of this scenario. Constraints arise both from strong quantum gravitational effects at the TeV scale, and more importantly from the production of massless Higher Dimensional gravitons with TeV suppressed couplings. Theories with n{gt}2 are safe due mainly to the infrared softness of Higher Dimensional gravity. For n=2, the six Dimensional Planck scale must be pushed above {approximately}30thinspTeV to avoid cooling SN 1987A and distortions of the diffuse photon background. Nevertheless, the particular implementation of our framework within type I string theory can evade all constraints, for any n{ge}2, with string scale m{sub s}{approximately}1thinspTeV. We also explore novel phenomena resulting from the existence of new states propagating in the Higher Dimensional Space. The Peccei-Quinn solution to the strong CP problem is revived with a weak scale axion in the bulk. Gauge fields in the bulk canmore » mediate repulsive forces {approximately}10{sup 6}{endash}10{sup 8} times stronger than gravity at submillimeter distances, as well as help stabilize the proton. Higher-Dimensional gravitons produced on our brane and captured on a different {open_quotes}fat{close_quotes} brane can provide a natural dark matter candidate. {copyright} {ital 1999} {ital The American Physical Society}« less
Naresh Dadhich - One of the best experts on this subject based on the ideXlab platform.
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gravitational collapse of type ii fluid in Higher Dimensional Space times
Physical Review D, 2002Co-Authors: S Ghosh, Naresh DadhichAbstract:We find the general solution of the Einstein equation for spherically symmetric collapse of type II fluid (null strange quark fluid) in Higher dimensions. It turns out that the nakedness and curvature strength of the shell focusing singularities carry over to Higher dimensions. However, there is shrinkage of the initial data Space for a naked singularity of the Vaidya collapse due to the presence of strange quark matter.
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on naked singularities in Higher Dimensional vaidya Space times
Physical Review D, 2001Co-Authors: S Ghosh, Naresh DadhichAbstract:We investigate the end state of the gravitational collapse of a null fluid in Higher-Dimensional Space-times. Both naked singularities and black holes are shown to be developing as the final outcome of the collapse. The naked singularity spectrum in a collapsing Vaidya region (4D) gets covered with the increase in dimensions and hence Higher dimensions favor a black hole in comparison to a naked singularity. The cosmic censorship conjecture will be fully respected for a Space of infinite dimension.
Sangjin Sin - One of the best experts on this subject based on the ideXlab platform.
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shear viscosity instability and the upper bound of the gauss bonnet coupling constant
Journal of High Energy Physics, 2009Co-Authors: Sangjin SinAbstract:We compute the Dimensionality dependence of �/s for charged black branes with Gauss-Bonnet correction. We find that both causality and stability constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in the infinite Dimensionality limit. We further show that Higher Dimensionality stabilize the gravitational perturbation. The stabilization of the perturbation in Higher Dimensional Space-time is a straightforward consequence of the Gauss-Bonnet coupling constant bound.
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shear viscosity instability and the upper bound of the gauss bonnet coupling constant
arXiv: High Energy Physics - Theory, 2009Co-Authors: Sangjin SinAbstract:We compute the Dimensionality dependence of $\eta/s$ for charged black branes with Gauss-Bonnet correction. We find that both causality and stability constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in the infinite Dimensionality limit. We further show that Higher Dimensionality stabilize the gravitational perturbation. The stabilization of the perturbation in Higher Dimensional Space-time is a straightforward consequence of the Gauss-Bonnet coupling constant bound.