Dimitrios Hristu-Varsakelis

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We propose a landmark-based representation of maps to be used for robot navigation and ezploration. Our approach is aimed towards mobile robots that operate over ezpan-sire, imprecisely known terrain without a single "global" map. Instead, a map is pieced together from local terrain and navigation data stored in a directed graph. Each of the graph's(More)
—We discuss the generation of symbolic feedback control sequences for navigating a sparsely-described and uncertain environment, together with the problem of sensing landmarks sufficiently well to make feedback meaningful. We explore the use of a symbolic control approach for mitigating the lack of a detailed map of the environment and for reducing the(More)
We revisit the problem of " sending information into the future " by proposing an anonymous, non-interactive, server-based Timed-Release Encryp-tion (TRE) protocol. We improve upon recent approaches by Blake and Chan, Hwang et al., and Cathalo et al., by reducing the number of bilinear pairings that users must compute, and by enabling additional(More)
A Networked Control System (NCS) is a control system in which the sensors and actuators are connected to a feedback controller via a shared communication medium. In an NCS, the shared medium can only provide a limited number of simultaneous connections for the sensors and actuators to communicate with the controller. As a consequence, the design of an NCS(More)
supported by the Army Research Office under the ODDR&E MURI97 Program Grant No. DAAG55-97-1-0114 (through Harvard University). This document is a technical report in the CDCSS series originating at the University of Maryland. Abstract We study the dynamics and explore the controllability of a family of sphere-plate mechanical systems. These are nonholonomic(More)
We propose a new server-based efficient protocol for time-release encryption (TRE), or - as sometimes referred to - sending information "into the future". As with other recently-proposed schemes, ours is based on the use of bilinear pairings on any Gap Diffie-Hellman group, allowing absolute release time of the encrypted data. Our protocol possesses the(More)
applies and teaches advanced methodologies of design and analysis to solve complex, hierarchical, heterogeneous and dynamic problems of engineering technology and systems for industry and government. Abstract— We study the stabilization of a networked control system (NCS) in which multiple sensors and actuators of a physical plant share a communication(More)