2DOF controller parametrization for systems with a single I/O delay

This note puts forward a parametrization of all stabilizing two-degrees-of-freedom controllers for (possibly unstable) processes with dead-time. The proposed parametrization is based on a doubly coprime factorization of the plant and takes the form of a generalized Smith predictor (dead-time compensator) feedback part and a finite-dimensional feedforward part (prefilter). Some alternative dead-time compensation schemes and disturbance attenuation limitations are also discussed.