Reciprocal variable feedback concept for design and control

System performance can be significantly improved when both the design of the plant and of the controller are considered concurrently. Control theory can be applied to diverse systems, including those that are physical in nature and many that are not. Despite the generality afforded by control theory, there are many situations in which opportunities are missed for using less conservative control laws and simpler overall implementations. This is due to formulations that do not explicitly reveal the existence of intrinsic information pertaining to the particular domain of application. Such is the case with many physical systems. The various constraints of physical reality (in the form of principles, laws, etc.) open several possibilities which can be exploited for system design and control. In this paper, we propose the Reciprocal Variable Feedback principle as a means for facilitating the control of plants with complicated nonlinear dynamics in the presence of parameter and/or structural uncertainty. The RVF principle exploits the effort-flow relationships associated with power interactions in order to assist in the design and control of physical processes. This is accomplished by using sensors instead of computation based models and can be implemented within many physical domains. A motion control example is used to provide insight into the nature of the principle. It is expected that in the future, additional principles will be identified and introduced for integrating design with the control of dynamic systems.