1. A controller for controlling a multi-variable input plant having a plurality of manipulatible variables (MVs) as inputs, and operable to provide an output, comprising: a predictive model of the dynamics of selected aspects of the operation of the plant for modeling the dynamics thereof, said model having at least two discrete models associated therewith that model at least two of the selected aspects, said at least two discrete models having different dynamic responses; an optimizer for receiving desired values for the selected aspects of the operation of the plant modeled by said model and optimizing the inputs to the model to minimize error between the predicted and desired values; and a control input device for applying the optimized input values to the plant after optimization thereof.