Ktisis Collection: Δημοσιεύσεις σε συνέδρια/ Conference papers

Mixed initiative control of autonomous vehicles

Sun, 29 Oct 2006 22:58:59 GMT

Title: Mixed initiative control of autonomous vehicles

Authors: Loizou, Savvas; Kumar, Vijay R.

Abstract: While there is extensive work on motion planning and control for navigation tasks with guarantees, there is no systematic way for human operators to modify the resulting plans without losing the guarantees. In this paper we propose a systematic way of composing behaviors resulting from human inputs with behaviors derived from navigation functions. The proposed controller is based on a new class of navigation function based controllers that posses weak Input-to-State stability properties. The resulting system has analytically guaranteed safety and convergence properties. The feasibility of the proposed methodology is demonstrated through simulation examples and hardware experiments.

Material invariant poromechanics properties of shales

Fri, 29 Oct 2004 22:58:59 GMT

Title: Material invariant poromechanics properties of shales

Authors: Constantinides, Georgios; Ulm, Franz Josef; Abousleiman, Younane N.

Abstract: Is it possible to break natural composite materials down to a scale where materials no longer change from one material to another, and upscale ('nanoengineer') the behavior from the nanoscale to the macroscale of day-to-day engineering applications? - This is the challenging question which is addressed in this paper by means of a combined experimental-theoretical multiscale microporomechanics approach and its application to shales. From this analysis it is found that the existence of material invariant properties (the mechanical 'blueprint') is a consequence of the combination of intermineral surface properties and characteristic packing densities, which dominate the nanomechanical response of colloidal material systems, rather than the much stiffer mineral properties. In return, at larger scales, the behavior of natural composites is a consequence of texture which can explain much of the large diversity of mechanical behavior of shale materials. These observations hold for most natural porous composites: bones, concretes, sandstones, etc., and is the focus of the GeoGenome Project, an international research effort, that aims at 'breaking the code' of all natural composite materials.

Decentralized motion control of multiple holonomic agents under input constraints

Tue, 29 Oct 2002 22:58:59 GMT

Title: Decentralized motion control of multiple holonomic agents under input constraints

Authors: Loizou, Savvas; Dimarogonas, Dimos V.; Zavlanos, Michael M.

Abstract: The navigation function methodology, established in previous work for centralized multiple robot navigation, is extended for decentralized navigation with input constraints. In contrast to the centralized case, each agent plans its actions without knowing the destinations of the other agents. Asymptotic stability is guaranteed by the existence of a global Lyapunov function for the whole system, which is actually the sum of the separate navigation functions. The collision avoidance and global convergence properties as well as input requirements are verified through simulations.

Biologically inspired bearing-only navigation and tracking

Sun, 29 Oct 2006 22:58:59 GMT

Title: Biologically inspired bearing-only navigation and tracking

Authors: Loizou, Savvas; Kumar, Vijay R.

Abstract: In this paper we develop controllers that are used for the control of individual or groups of vehicles based only on sensors that provide bearing information. Our inspiration is derived from the observation that many ant species use landmark retinal positions to navigate without having any range information. This is specially relevant to vision-based controllers for vehicles because cameras provide very good bearing information but relatively poor range information. We present a provably correct bearing-only navigation controller and a methodology for tracking that lends itself to control of formations. The proposed feedback controllers are shown to have analytically guaranteed properties. The effectiveness of the proposed controllers is demonstrated through computer simulations.