Type of Document Dissertation Author Seward, Lori Welte Author's Email Address firstname.lastname@example.org URN etd-32998-103459 Title Preventive Maintenance for a Multi-task System Degree PhD Department Industrial and Systems Engineering Advisory Committee
Advisor Name Title Nachlas, Joel A. Committee Chair Ioannou, George Committee Member Kobza, John E. Committee Member Rakes, Terry R. Committee Member Schmidt, J. William Committee Member Keywords
- Preventive Maintenance
- Renewal Theory
Date of Defense 1998-04-02 Availability unrestricted AbstractThis research models the behavior of a multi-task system with respect to
time. The type of multi-task system considered here is one in which not all
system components are required to perform each task. Each component may,
however, be used for more than one task. Also, it is possible that some of the
components may be required for every task that the system performs.
The components that are required for a subset of the tasks are considered
to be intermittently demanded components and those components required for
every task are continuously demanded components. This modeling approach
assumes that the system is subject to a Modified Age Replacement Policy
(MARP.) With a MARP the intermittently demanded components are maintained
during their idle periods and the continuously demanded components are replaced
according to their age replacement times.
A renewal theory approach is used to develop an availability expression
for the multi-task sytem. Past research has focused on systems consisting of
continuously demanded components and typically does not distinguish between
elapsed clock time and elapsed operating time in the renewal density function
expressions. This research recognizes that the operational age of an intermittently
demanded component is different than the chronological age of the component. The renewal density function and availability measures are modeled using joint
density functions defined on both clock time and operating time.
The expressions are evaluated numerically using a multidimensional
numerical integration routine. The results show logical behavior of the joint
density functions used to define the availability measure. The availability
measure also displays behavior consistent with the definition of a multi-task
system. This model is an important development in the need for stochastic
models of highly complex systems. The model is also a first step in defining
performance measures for systems composed of both intermittently demanded
components and continuously demanded components.
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