Low-order controller design for SISO systems using coprime factors and LMI

This paper develops a low-order controller design method for linear continuous time-invariant single-input, single-output systems requiring only the solution of a convex optimization problem. The technique integrates several well-known results in control theory. An important step is the use of coprime factors so that, based on strictly positive real functions, feedback stabilization using low-order controllers becomes a zero-placement problem which is convex. From this result, we develop algorithms to solve two optimal control problems