Overview

This application of SRI's procedural reasoning technology emphasizes the control of multiple, loosely-coupled, intelligent processes to detect and localize submarines. Depending upon the extent of the area of uncertainty surrounding a detected submarine's location, hydrophon deployment patters are intelligently selected and applied until the uncertainty is resolved.

Domain

Aircraft like the P-3C Orion anti-submarine patrol aircraft detect and localize submarines by deploying specific patterns of sonobuoys - sensitive acoustic transducers - to listen for telltale sounds emitted by the submarines. By fusing the information from multiple sonobuoys, it is possible to make accurate determinations of the location of a submarine. This demonstration simulates the detection and localization of a submarine by a P-3C aircraft. It accomplishes this by selecting sonobuoy patterns for deployment based on its current information about the sub's position and the location of the aircraft, deploying selected patterns, interpreting the information presented by the sonobuoys, and then determining its next action. The search terminates when either the submarine has been located within an area that is sufficiently small, or the P-3C runs out of sonobuoys.

Application

The system is built on top of a collection of six PRS agents (top center): the time manager, interface manager, sonobuoy manager, airplane, submarine, and locator. The PRS message-passing facility is used extensively to provide shared knowledge and coordination among the various agents. The time manager provides the underlying temporal synchronization for the system while the airplane and submarine agents simulate the actions of the P-3C and the submarine to be tracked. The sonobuoy manager monitors the submarine's position and generates simulated contacts when the submarine enters the detection zone of any currently active sonobuoys. Responsibility for strategic decisions rests with the locator agent. Based on situational information, the locator determines when and where to deploy various patterns of sonobuoys and requests the airplane agent to undertake actual deployment of the patterns. The criteria used for pattern selection include recent contact histories and an estimate of a bounding region that contains the submarine. The bounding region, which is represented as a collection of polygons, is recomputed at each time cycle, taking into account estimated movements of the submarine and new contacts. The locator will continually choose and request deployment of patterns until the bounding region has been reduced below a prespecified success threshold. The interface agent maintains a graphical display of the scenario, including airplane and submarine positions, deployed sonobuoys, and the current bounding region (lower right).

Performance

The submarine localization and tracking system provides a good demonstration of the ability of PRS to smoothly integrate goal-driven and event-driven behavior. Within this system, a specific detection strategy can be pursued based on available situational data but rapidly modified or replaced in response to incoming information. Other capabilities of PRS that play an important role in the demonstration system include resource management to keep track of sonobuoy stores and available communication channels, metalevel reasoning for selecting among alternative actions, and the use of multiple agents with message-passing to provide modularity and flexibility.

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Karen L. Myers, <myers@ai.sri.com>
Artificial Intelligence Center
SRI International

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