The availability of multifunctional systems with multistate components

Abstract

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.