Joint optimal mission aborting and replacement and maintenance scheduling in dual-unit standby systems

Abstract

This paper models a dual-unit standby system with non-identical, reusable units that perform the mission task alternatively according to a pre-specified replacement and maintenance schedule (RMS). When one unit is online operating, the other unit undergoes maintenance of a particular type determined by the RMS. In the case of one unit failing and the amount of work completed before the unit failure not exceeding a threshold value, the system aborts the primary mission and immediately activates a rescue procedure to avert or alleviate the risk of system failure and thus any associated damages. Both the RMS and the mission abort threshold parameter adopted can affect the mission success probability (MSP) significantly. This paper makes contributions by formulating and solving a constrained optimization problem that determines the joint RMS and mission abort policy, maximizing the MSP while meeting a constraint on the damage avoidance probability (DAP). A probabilistic method is suggested to evaluate the MSP and DAP of the considered system. Based on the string solution representation designed in this work, the genetic algorithm is then implemented to solve the optimization problem. A case study on a dual-pump liquid transfer system used in the chemical reactor is conducted to demonstrate the proposed model, and optimization solutions balancing MSP and DAP.