Using optimality conditions, it is proposed to quantify the coupling between designing an artifact (i.e., the "plant") and designing its controller. For the first time, this quantification of coupling will be used to understand when the two problems can be solved sequentially (i.e., design the artifact first, then its controller) so as to simplify the design process (i.e., disciplinary decoupling, and reduced product development times via parallel design) and when they need to be solved simultaneously (i.e., combined design of the artifact and its controller) to arrive at superior performance. Again, for the first time, the quantification of this coupling will be used to investigate several important conjectures: (1) tightening performance specifications increases coupling; (2) controllability of the plant is related to coupling; (3) increased uncertainty increases coupling, and there exists a tri-lateral coupling between the artifact design, modeling and control problems. The results of the research will be applied to compelling applications, such as fuel cell vehicles and MEMS. The results of this research are expected to yield, not only a method for quantifying coupling between plant and controller design, but also to provide general methods and principles of design based upon the trade-off between convenience of decoupling versus best system performance achievable with a more complex co-design approach. The synergistic integration of mechanical, electrical, electronic, computer, optical, and control disciplines what has become known as mechatronics characterizes the design of modern engineered systems. Mature technologies, such as automobiles, are gradually yet radically changing through increased controls in powertrain (e.g., controls for idle speed, air/fuel ratio, spark timing, exhaust gas recirculation, valve timing, cylinder displacement and automatic transmissions), vehicle dynamics (e.g., anti-lock braking and traction control, cruise control, four wheel steering, active suspensions, drive-by-wire) and active safety (e.g., airbags, electronic stability control, headway control). Effective and practical introduction of new energy technologies, such as fuel cells, depends critically on designs with proper control functions. Applications of breakthrough technologies, such as MEMS and biotechnologies, to real products may not be possible without a harmonious integration of the design and control functions. The term "co-design" (combined design) refers to the fact that the design of the "plant" (or "controlled system") in the controls jargon and of the "controller" must be done in a combined, integral manner. This project aims to provide an important theoretical foundation for such co-design: a quantification of the coupling between the design and control functionality based on optimizing the overall system performance. Successful results of this research will have widespread impact on the design of a variety of mechatronic systems (e.g., automotive controls, fuel cells, MEMS).
