  We consider the problem of designing a feedback controller that guides the
input and output of a linear time-invariant system to a minimizer of a convex
optimization problem. The system is subject to an unknown disturbance that
determines the feasible set defined by the system equilibrium constraints. Our
proposed design enforces the Karush-Kuhn-Tucker optimality conditions in
steady-state without incorporating dual variables into the controller. We prove
that the input and output variables achieve optimality in equilibrium and
outline two procedures for designing controllers that stabilize the closed-loop
system. We explore key ideas through simple examples and simulations.
