The Control Architecture for Multirobot Outpost (CAMPOUT) is a distributed-control architecture for coordinating the activities of multiple robots. In the CAMPOUT, multiple-agent activities and sensor-based controls are derived as group compositions and involve coordination of more basic controllers denoted, for present purposes, as behaviors.
The CAMPOUT provides basic mechanistic concepts for representation and execution of distributed group activities. One considers a network of nodes that comprise behaviors (self-contained controllers) augmented with hyper-links, which are used to exchange information between the nodes to achieve coordinated activities. Group behavior is guided by a scripted plan, which encodes a conditional sequence of single-agent activities. Thus, higher-level functionality is composed by coordination of more basic behaviors under the downward task decomposition of a multi-agent planner (see figure).
Robotics is a highly multidisciplinary field that requires efficient integration of many components (e.g., perception, mapping, localization, control, and learning)that involve diverse representations, frameworks, and paradigms (e.g., classical control theory, artificially intelligent planners, estimation theory, data fusion, computer vision, utility theory, decision theory, fuzzy logic, and multiple-objective decision making). The CAMPOUT provides a conceptual infrastructure for consolidating diverse techniques to enable the efficient use and integration of these components for meaningful interaction and operation.
The methodology of the CAMPOUT features a few elementary architectural mechanisms for (a) behavior representation, (b) behavior composition, (c) group coordination of teams, and (d) interfaces among (a), (b), and (c). For the purposes of the CAMPOUT, a behavior is defined and represented as a mapping from a percept (defined here as a description of raw or processed sensory input) or a sequence of percepts to an action or sequence of actions.
The mapping assigns, to each possible action, a degree of preference that ranges from 0 for most undesired to 1 for most desired. This definition of a behavior is a general recipe that does not dictate how the mapping is to be implemented. It does not exclude implementation by use of a look-up table, a finite-state machine, a neural network, an expert system, a control law, or any other such means. Each behavior can be implemented using whichever approach is appropriate.
Behavior composition is the mechanism used for building higher-level behaviors by combining lower-level ones. The activities of lower-level behaviors are coordinated within the context of the task and objective of a higher-level behavior. An explicit design goal of the CAMPOUT has been to support not one but an arbitrary number of behavior-coordination mechanisms (BCMs). The architecture can be extended by incorporation of new BCMs.
Because different BCMs often require different behavior representations, the CAMPOUT involves utilization of a multivalued behavior representation that is general enough for a large class of applications. BCMs can be divided into two main classes: arbitration and command. The CAMPOUT supports both classes.
In the CAMPOUT, the problem of coordinating a group of robots is formulated as one of coordinating multiple distributed behaviors across a network that includes more than one decision maker. In behavior coordination, one is basically concerned with resolving or managing conflicts between mutually exclusive alternatives and between behavioral objectives. Because this is as true for individual as for group decision-making, the difference between individual and group decision-making is inessential, and both can be studied in the same conceptual framework. Mechanisms that are typically used for coordination of the behavior of one robot can then be used for coordination of behaviors running on a network of robots. Hence, for example, a control loop could use sensors on one robot to drive a different robot.
This work was done by Hrand Aghazarian, Paolo Pirjanian, Paul Schenker, and Terrance Huntsberger of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Information Sciences category. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
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Refer to NPO-30345, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
An Architecture for Controlling Multiple Robots
(reference NPO-30345) is currently available for download from the TSP library.
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