A unified Smith predictor based on the spectral decomposition of the plant

We point out a numerical problem in the well-known modified Smith predictor and propose a unified Smith predictor (USP) which overcomes this problem. The proposed USP combines the classical Smith predictor with the modified one, after a spectral decomposition of the plant. We then derive an equivalent representation of the original delay system, together with the USP. Based on this representation, we give a controller parameterization and we solve the standard H 2 problem.