Knowing that the plant parameters can vary within their lower and upper bounds, this parametric uncertainty is formulated as an additive perturbation in the transfer function matrix. It is important to note that the controller be designed with respect to worst case uncertainty for each λij. This can be achieved by performing an optimization procedure given by (61) for 200 frequencies. Here an element by element uncertainty bound model is used for the characterization of upper bound of the uncertainty matrix. Then wij , which satisfies (62) for each λij is given in matrix form as,.
