We face countless challenges in the 21st Century: national defense, building and transportation infrastructure, energy demand and clean water, frequent natural disasters, global market competition, rising healthcare costs, and an ageing population, to name a few.

While daunting, these problems share several common features. They are complex and multifaceted, they have emergent and unpredictable behavior, and their solutions must integrate knowledge from multiple disciplines in engineering and beyond while managing a wide range of risks and uncertainties. Unfortunately, common approaches to solving these problems are ad hoc and reductionist, often resulting in cost over-runs, schedule delays, and solutions that perform poorly. It is clear that we have reached the limits of what these approaches can do. To proceed, we need a more rigorous and deeper understanding of complex engineered systems and how they should be designed.

With this in mind, we organized this Special Issue to help establish a foundation on which to build future research to support the design of complex engineered systems. Over 60 technical papers were submitted for review to the Special Issue. All papers went through the rigorous peer-review process that the Journal of Mechanical Design upholds. While the three of us administered most of these manuscripts, we would like to thank Drs. Wei Chen, Olivier de Weck, Michael Kokkolaras, Zissimos Mourelatos, Karthik Ramani, and Avinash Singh for their assistance coordinating the reviews of some papers. Finally, we would also like to thank all those who helped review all of these papers for the Special Issue.

There are 18 papers that appear in this Special Issue. The paper by Simpson and Martins, based on a report from a recent NSF workshop, describes the current state of the art of multidisciplinary design optimization and identify many of the challenges and opportunities that our research community must face.The remaining papers are organized into four groups based on common themes in the papers. These are: (1) Representation, Change and Reuse, (2) Architectures and Interdependencies, (3) Convergence, Resilience and Success Indicators, and (4) Multidisciplinary Design Optimization (MDO). A summary of the papers in each group follows.

There are five papers in the Representation, Change and Reuse group. They present new ways of representing the design of complex engineered systems or evaluating change propagation or opportunities for reuse within such systems. For instance, Chowdhury et al. present a new framework to support platform design for a family of products. Zhang et al. review the state of the art for integrated layout design for multicomponent systems, and Su offers a model identification approach based on fuzzy set theory. Siddiqi et al. present a system-level understanding and approach for a posteriori analysis of design changes within complex engineered systems. Finally, Kwak et al. analyze results of data from an e-waste collection center that can be used in support of design for reuse.

The five papers in the Architectures and Interdependencies group highlight the importance of both product and process architecture and modeling interdependencies within an architecture. Albers et al. present a new approach to design architectures that utilize function-form dependencies. Chiriac et al. analyze the impact of granularity during system decomposition on modularity for 88 idealized system architectures and an example of a complex system. Sosa et al. present results from a study in which a few subsets of components or hubs in a complex system architecture have a disproportionate number of dependencies with other components; they argue that the presence of hubs in complex systems improves their reliability. Meanwhile, Mane et al. discuss the advantages and disadvantages of interdependencies in a network of coupled systems. Finally, Devendorf and Lewis study the dependence of solution stability on the architecture of the solution process.

There are four papers in the Convergence, Resilience and Success Indicators group. In these papers, the focus is on the role of convergence and resilience of complex engineered systems as well as metrics for successful development of such systems. Wang et al. present a customer-driven modularized approach, including metrics, for design of products that “converge” from a number of distinct functionalities that existing product categories already provide. Youn et al. present an approach for designing resilient systems based on system reliability, prognostics and health management, and optimization methods. Saha and Ray present an approach for robust optimization of systems using evolutionary methods, and Kazerouni et al. present metrics that can be used as success indicators in new product development.

Finally, there are three papers in the MDO group. These papers highlight recent advancements in algorithms and frameworks to support MDO as well as new applications of MDO methods. Alexander et al. present a novel constraint management approach for MDO. Brezillon et al. offer an MDO framework tailored to applications involving small-scale supersonic aircraft. Finally, Ruiyi et al. introduce a three-level multi-objective collaborative optimization approach to support the design of complex engineered systems.

Taken together these contributions highlight the current efforts in the community and give us new avenues to investigate. Our hope is that this Special Issue stimulates further research and helps to focus interest on the multitude of problems facing the design of complex engineered systems.