Showing papers by "Paul Morris published in 1999"

Managing Temporal Uncertainty Through Waypoint Controllability

Abstract: Simple Temporal Networks have proved useful in applications that involve metric time. However, many applications involve events whose timing is not controlled by the execution agent. A number of properties relating to overall controllability in such cases have been introduced in [Vidal and Ghallab, 1996] and [Vidal and Fargier, 1997], including Weak and Strong Controllability. We derive some new results concerning these properties. In particular, we prove the negation of Weak Controllability is NP-hard, confirming a conjecture in [Vidal and Fargier, 1997]. We also introduce a more general controllability property of which Weak and Strong Controllability are special cases. A propagation algorithm is provided for determining whether the property holds, and we identify tractable cases where the algorithm runs in polynomial time.

Next Generation Remote Agent Planner

Abstract: In May 1999, as part of a unique technology validation experiment onboard the Deep Space One spacecraft, the Remote Agent became the first complete autonomous spacecraft control architecture to run as flight software onboard an active spacecraft. As one of the three components of the architecture, the Remote Agent Planner had the task of laying out the course of action to be taken, which included activities such as turning, thrusting, data gathering, and communicating. Building on the successful approach developed for the Remote Agent Planner, the Next Generation Remote Agent Planner is a completely redesigned and reimplemented version of the planner. The new system provides all the key capabilities of the original planner, while adding functionality, improving performance and providing a modular and extendible implementation. The goal of this ongoing project is to develop a system that provides both a basis for future applications and a framework for further research in the area of autonomous planning for spacecraft. In this article, we present an introductory overview of the Next Generation Remote Agent Planner. We present a new and simplified definition of the planning problem, describe the basics of the planning process, lay out the new system design and examine the functionality of the core reasoning module.