Reliability and availability measures are well defined for simple systems, but many real
systems are not simple. Many systems are designed to perform more than one task. In
addition, these systems may be performing at one of many levels. When these factors are
not considered, the system availability analysis changes considerably.
Many modern systems are designed to perform more than one function. Sols (1992) and
Sols and Nachlas (1993) discuss the importance of multifunctional systems and the need to
redefine availability to accommodate them. Furthermore, in most traditional reliability
theory, components are assumed to be either functioning or failed which oversimplifies
many physical situations. Multistate models have been developed in the literature, and
conditions for the system structure function have been defined.
Multifunctional systems and systems with multistate components have been discussed in
the literature individually, however a model for systems with both multifunctional
capability and potentially degraded components has not been discussed. By synthesizing
the previous work on multistate systems and on multifunctional systems, this research
presents a general model for multifunctional, multistate systems. The model is specialized
to a general class of multifunctional, multistate systems. Expressions are derived for the
element, function, and system availability. The availability for an example system is then
computed.
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