on failure modes for components that is input through use of a variety of representations, including logic models/diagrams, event/fault trees, directed graphs, Bayesian networks, process trees, and reliability block diagrams; (3) system process, using inputs from physics and chemistry, mechanical engineering, quality control tests, assembly, and testing at various levels (system, subsystem, and component); and (4) inputs concerning the reliability of components in analogous systems, and expert opinion on the reliability of the components. All of these inputs are documented in a knowledge base that provides information at customized levels for various queries. Inputs for a given system are also available to provide information concerning the performance of similar or related systems in the future. These initial assessments are updated in accordance with the receipt of new information and test results. (Updates are also based on refinements to system structure or changes to requirements or performance measures.)

PREDICT tracks performance as system development proceeds. Once a system has been fielded, PREDICT can be used to track performance in the field; that is, it can continuously update reliability assessments on the basis of new information (e.g., on the aging of the system).

PREDICT also provides a platform that facilitates consideration of various action items, such as whether one can support a system in the field or how the number of maintenance actions can be reduced once the system has been fielded. PREDICT can also support decisions involving either the development of a new system or a choice among several system designs through balancing of the costs of development and the costs of fielding to arrive at a system that minimizes life-cycle costs.

As an example, consider an air-to-air heat-seeking missile. The major subsystems are the warhead, the missile, the aircraft, command and control, and logistics and maintenance. Taking the command and control subsystem in more detail, the aircraft has power, avionics, environmental, acquisition and fire control, flight structure, launching, flight control, and missile interface elements, as well as human intervention. There are also complex interactions between subsystems that act across major subsystems. PREDICT attempts to represent all of this structure using various forms of sensitivity analysis.

PREDICT has been used successfully by Delphi Automotive Systems and in the nuclear weapons program at Los Alamos National Laboratory. PREDICT can also be implemented in dynamic environments where testing is not feasible, such as in the nuclear weapons program.



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