Nikitas M. Sgouros

The autonomous mobile robot SENARIO: a sensor aided intelligent navigation system for powered wheelchairs

The SENARIO project is develoing a sensor-aided intelligent navigation system that provides high-level navigational aid to users of powered wheelchairs. The authors discuss new and improved technologies developed within SENARIO concerning task/path planning, sensing and positioning for indoor mobile robots as well as user interface issues. The autonomous mobile robot SENARIO, supports semi- or fully autonomous navigation. In semi-autonomous mode the system accepts typical motion commands through a voice-activated or standard joystick interface and supports robot motion with obstacle/collision avoidance features. Fully autonomous mode is a superset of semi-autonomous mode with the additional ability to execute autonomously high-level go-to-goal commands. At its current stage, the project has succeeded in fully supporting semi-autonomous navigation, while experiments on the fully autonomous mode are very encouraging.

Dynamic dramatization of multimedia story presentations

We describe a novel dynamic dramatization method for narrative presentations. This method accepts as input the original story material, along with a description of its plot written in a special-purpose language. It then analyzes the plot to iden~ interesting dramatic situations in the story. Based on this content analysis, a presentation manager organizes the presentation and enriches it with appropriate multimedia effects. These effects are associated with interesting dramatic situations, and serve to increase suspense and emphasize plot developments in the narrative. Our method can be used for the development of intelligent front-ends to story databases, for directing assistants in computer-based renditions of narrative works, or for real-time direction of interactive entertainment systems. We are integrating this system in an interactive storytelling environment for Greek mythology.

Global path planning for autonomous qualitative navigation

We describe a novel global path planning method for autonomous qualitative navigation in indoor environments. Global path planning operates on top of a qualitative map of the environment that describes variations in sensor behavior between adjacent regions in space. The method takes into consideration the global topology of the environment and applies a set of criteria that can minimize the errors in the navigational accuracy of a robotic wheelchair. Our approach uses a modified version of the Dijkstras shortest path algorithm that takes into consideration the curvature of the trajectory and the off-wall distance of the map points. The algorithm computes in real-time a set of optimal paths for reaching the destination. We have tested our global path planning method in simulation in representative indoor environments with above average complexity. Based on these experiments we have determined empirically a set of values for the parameters of the algorithm that almost always lead to the selection of optimal paths in these environments.

Localized qualitative navigation for indoor environments

We describe a novel architecture for indoor navigation, based on qualitative representations of the variations in the interactions between the robot and its environment. We use these representations to localize and guide planning and reaction. The system accepts off-line as input a topological diagram of the environment. It then uses numerical simulation to generate a map, describing qualitative variations in the sensor behavior between adjacent regions in space. An off-line planner stores localized navigation information at each point in the map. During execution, an adaptive controller uses a short-term memory to improve its operation. The qualitative nature of our method, along with the localization performed by the topological planner result in a compact map representation and in linear-time performances for position estimation and path planning during execution. This architecture has been tested in simulation. Our results show that the proposed navigation method is tolerant of sensor inaccuracies, both in obstacle detection and orientation.

ATTRIBUTE GRAMMAR BASED MODELING OF CONCURRENT CONSTRAINT LOGIC PROGRAMMING

The development of more powerful Concurrent Constraint Logic Programming (CCLP) languages depends largely on the development of environments that facilitate the specification and integration of constraints in the semantics of a logic program and automatically extract the inherent parallelism of Logic Programming. This paper presents a novel method for automating the parallel AND/OR execution of CCLP applications. This method consists of two stages. The first stage translates a logic program into an equivalent Attribute Grammar providing a common language in which the specifications of constraints and the semantics of a logic program can be expressed. The second stage evaluates this Attribute Grammar using MPAGE, a Multipass Parallel Attribute Grammar Evaluation algorithm. Support for the processing of constraints in the logic program is provided with the creation of a dependency graph between the variables of a logic rule during the first stage. Using this dependency graph MPAGE delays, if necessary, the evaluation of variables in a constraint until they become bound at some later point in processing. As a result our method supports rule representations in CLP languages with no restrictions on the ordering of subgoals. Furthermore, during execution MPAGE allows single rules in a CLP program to deal with multiple assignments of bindings, thus generating a minimal number of processes. Finally, this method is independent from the underlying hardware and its memory organization, therefore it can be implemented on both shared and distributed memory systems.

Multimedia presentation techniques for interactive plots

Interactive plots support the creation of engaging stories or games that are meaningfully interactive. The authors describe a novel multimedia presentation method for interactive plots that dynamically links story content with appropriate presentation styles. This method accepts at each point in time a set of interactions between the story or game characters. It then analyzes these interactions to identify interesting dramatic situations and enrich them with appropriate multimedia effects. These effects serve to increase suspense and emphasize plot developments during story delivery. They are using this method for the design and real-time direction of interactive entertainment systems.

Dependency-Directed Binding of Variables For Constraint Logic Programming

Constraint Logic Programming (CLP) environments should be able to delay, if necessary, the evaluation of variables in a constraint (e.g. equation) until they become bound at some later point in processing. This paper presents a general method for supporting the automatic creation of delayed bindings in CLP environments that is applicable not only in the case of constraints but for any predicate in a logic rule as well. Consequently this method supports rule representations in CLP languages with no restrictions on the ordering of subgoals.