Design of Complex Engineered Systems

Many past editorials have discussed definitions of design, ointing out the wide variation across individuals and industries. e adhere to a definition that recognizes design to be a matter of aking rational decisions regarding available alternatives in order o achieve one’s stated preference. In an upcoming special issue of his journal, research articles on the topic of “designing complex ngineered systems” are being invited. This begs the question: hat is a complex engineered system? Further, what are the nique design challenges of such systems? We define complex systems to be those for which tightly oupled interacting phenomena yield a collective behavior that annot be derived by the simple summation of the behavior of the arts. In essence, these are highly interdisciplinary systems in hich the existence of inherent couplings potentially leads to irational results. Complex systems may be biological human ody , natural rain forests , or engineered aerospace, naval arhitectures, drilling platforms, and medical devices . Growing human needs in national defense, environmental susainability, medical advancements, and human prosperity, in genral, have been drivers in the increased complexity seen in engieered systems. However, whether one is designing a new aterial for a particular behavior across scales or a large-scale ransportation system, involving numerous interacting disciplines, he inherent couplings wreak havoc with the practice of imposing traditional structured hierarchical design process. Further, there s little room today for an antiquated organizational approach ooted in single discipline superiority. In general, present efforts to address complexity in engineering esign tend toward managing the complexity through more proesses rather than attempting to rigorously understand it through heory or even exploit it to improve system performance. While he reliance on traditional methodologies and processes tied to a articular organizational structure can have detrimental results at he smaller scale, the failures are magnified substantially for largecale complex products. Today, the most common system engieering approaches involve using a hierarchical decomposition ithin a requirements-driven framework. Even the most meticuous implementation of this approach when used for large-scale omplex systems such as military aircraft can still lead to mindoggling cost overruns in the hundreds of millions of dollars and ubstantial time delays that set projects back by years or even ead to project cancellation . We can and we must reverse this attern. The widespread and rapidly growing prevalence of comlex engineered systems means that the critical gaps in design heory and methodology have pervasive and damaging impacts rom small to large scales. Now, more than ever, our engineering design community must ise to the challenge of addressing these issues. However, what