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The reduction is described of the operation and fault diagnostics of a Deep Space Network heat exchanger to a rule base by the application of propositional calculus to a set of logic statements. The value of this approach lies in the ease of converting the logic and subsequently implementing it on a computer as an expert system. The rule base was w

Author: NASA Technical Reports Server (NTRS)

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N89-10205 TDA Progr_s Report 42-94 April-June 1988 lq- Heat Exchanger Expert System Logic R.
Cormier Radio Frequency and Microwave Subsystems Section This article describes the reduction of the operation and fault diagnostics of a DSN heat exchanger to a rule base by the application of propositional calculus to a set of logic statements. The value of this approach lies in the ease of converting the logic and subsequently implementing it on a computer as an -expert system.
-The rule base was written in Process Intelligent Control (PICON) software. I.
Introduction The application calculus has great The controls of formal systems analysis and propositional value in the design of an -expert system- rule base, where the need is to model knowledge.
Propositional calculus is a formal logic system from which conclusions are deduced independent of the structure of the propositions. The conclusions follow uniquely from the truth or falsity of the propositions. Once a knowledge base has been converted to propositions, assuming it has been done correctly, the process of deduction cannot lead to contradictions or to invalid conclusions.
One of the consequences is that, given an appropriate model, every deduction is a tautology.
A description of formal systems and propositional calculus can be found in [I].
The breadboard heat exchanger expert system is described in [2]. The task described in this article involved the conversion were first described in terms of factor. Two fans are provided, but these are only partially redundant. Under certain conditions, both fans are required. In addition, a number of other failures can be tolerated provided the heat exchanger is operated locally.
The Pumps Alternating command can be bypassed with a local switch, in which case both pumps may be operated simultaneously. All of these conditions were described and incorporated in the rule base, as the expert system needed the capability to distinguish between and not...






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