Liu, TianchenCo-design refers to the process of integrating optimization of the physical design with a controller for a system. The challenge in co-design is that the optimization is simultaneously applied to both static/time-invariant (e.g., physical plant design) variables and dynamic/time-variant (e.g., state and control) variables, which can be coupled with each other. The objective of this dissertation is to explore new formulations and approaches in co-design for multi-subsystem and vehicle routing-and-control problems. Specifically, four research questions are considered and resolved. In Research Question 1 (RQ1), the critical issue is how to formulate a class of multi-subsystem co-design problems with convex physical design subproblems and linear quadratic regulator control subproblems, and construct a decentralized solution approach for such problems. In Research Question 2 (RQ2), solution methods for a broader class of multi-subsystem co-design problems than those considered in RQ1 are investigated. In Research Question 3 (RQ3), the question is whether, in the context of co-design, the combined routing and control costs of a fleet of vehicles can be improved if optimal control is introduced into the routing. Finally, an extension of RQ3 is considered in Research Question 4 (RQ4), where the possibility of constructing an integrated vehicle routing-and-control problem with load-dependent dynamics is investigated. Beyond the articles published by the author of this dissertation, the proposed research questions, models and methods presented have not been considered elsewhere in the literature.enDissertationMechanical engineeringCo-design OptimizationVehicle Routing Problems