Incorporating flexibility into system design : a novel framework and illustrated developments

Abstract

Many complex engineering systems in general, and aerospace systems in particular, are highly ''optimized" designs, fielded to provide mission superiority or market competitive advantage. Two noticeable trends over the last few decades in engineering design have been increased optimization of the system architecture (mission-specific systems), and increased system design lifetime or service life. Unfortunately, many complex engineering systems often outlive the mission they were designed to address or the market they were designed to service (the mission being no longer relevant in the new environment or context, or in the case of a commercial system, the market has evolved beyond the need for that particular service). Because such complex engineering systems were initially highly optimized for that specific mission or market, they are often unable to modify their capabilities in order to address the new missions or markets that arise with time. In this thesis, we develop a framework that allows a system to be designed to maintain the competitive advantage despite environmental change. The resulting flexible system can refocus its core capabilities to meet new mission requirements. Within the context of this work, refocusing is achieved by exchanging key components needed for the old mission, for those needed in the new mission. A strategy to increase a system's flexibility was adapted from the art of platforming. A flexible system would enable the customer to exchange the obsolete components used for an old mission, for the components needed for a new mission (termed the frame), at a sufficiently low cost, and sufficiently short downtime.

(cont.) That which is not upgraded, and remains constant through all transitions of mission focus, is termed the platform. Increasing a system's flexibility can causes an associated detriment to the systems performance, acquisition cost, and other system evaluation metrics. Presented herein are tools to perform a cost-benefit analysis for increasing levels of flexibility. The flexibility of a system is evaluated by weighing a systems ability to fulfill different mission against the cost and time required to transition the system from one mission focus to another. The value of flexibility is seen as the performance it enables compared to the cost and time required to transition between mission focii. The developed methodology is then applied to design a mission flexible Unmanned Aerial Vehicle. Matrices to evaluate the costs and benefits of flexibility are further explained in the context of the case study. The results show that the degree of flexibility can be adjusted to trade between the point performance of each mission, and the cost and time required to transition between missions. The case study has been included to help clarify some of the trade offs inherent to increasing flexibility, and to further discuss the tools at hand to quantify the value of each option.