Towards a Simpler Selection Process for Maintenance Strategies

Recent research at four large manufacturing sites in the North East of England showed that maintenance organisations were failing because they were locked in a cycle of quick fix and mend despite deploying extensive planned maintenance policies. Consequently they were unable to plan and formulate strategies because they did not have the time. Simple and quick tools were needed to select the best maintenance approach for the machines and the plant. Two possible selection tools were developed. Firstly a truth table was produced based on the key characteristics of each maintenance approach and these mapped against simplified failure mode combinations. This offered a quick and easy selection method for machines, based on failure mode patterns. Secondly, the macro level was addressed using a conceptual model employing a 2x2 matrix. This consisted of two axes, the level of machine failures and the level of improvement activity. The resulting framework was used to predict how maintenance organisations would progress from a state of reactive maintenance towards world class. Then informed by the truth table it was possible to select an appropriate maintenance approach which was most suitable for each stage. It is suggested that these two methods offer simple and quick approaches to guide vital maintenance decision making at plants in difficulty. This of course does not preclude the need to develop maintenance strategies but rather facilitates this process by freeing up time and resources

The Temporal Logic of the Tower Chief System

The purpose is to describe the logic used in the reasoning scheme employed in the Tower Chief system, a runway configuration management system. First, a review of classical logic is given. Defensible logics, truth maintenance, default logic, temporally dependent propositions, and resource allocation and planning are discussed

A beginner's guide to belief revision and truth maintenance systems

This brief note is intended to familiarize the non-TMS audience with some of the basic ideas surrounding classic TMS's (truth maintenance systems), namely the justification-based TMS and the assumption-based TMS. Topics of further interest include the relation between non-monotonic logics and TMS's, efficiency and search issues, complexity concerns, as well as the variety of TMS systems that have surfaced in the past decade or so. These include probabilistic-based TMS systems, fuzzy TMS systems, tri-valued belief systems, and so on

Plausible inference: A multi-valued logic for problem solving

A new logic is developed which permits continuously variable strength of belief in the truth of assertions. Four inference rules result, with formal logic as a limiting case. Quantification of belief is defined. Propagation of belief to linked assertions results from dependency-based techniques of truth maintenance so that local consistency is achieved or contradiction discovered in problem solving. Rules for combining, confirming, or disconfirming beliefs are given, and several heuristics are suggested that apply to revising already formed beliefs in the light of new evidence. The strength of belief that results in such revisions based on conflicting evidence are a highly subjective phenomenon. Certain quantification rules appear to reflect an orderliness in the subjectivity. Several examples of reasoning by plausible inference are given, including a legal example and one from robot learning. Propagation of belief takes place in directions forbidden in formal logic and this results in conclusions becoming possible for a given set of assertions that are not reachable by formal logic