1. A method for controlling a nonlinear system, comprising: a linear controller receiving inputs representing measured variables of the system, wherein values of the measured variables of the system are in a first operating region, and wherein the linear controller is operable to determine predicted control values for manipulable variables that control the system; executing a nonlinear model of the system, wherein the nonlinear model has been trained to represent operation of the system over a specified region of the system's operating space; initiating a change in operation of the system, wherein the change operates to move the values of the measured variables of the system from the first operating region to a second operation region, wherein said initiating comprises modifying the nonlinear model in accordance with the change in operation of the system; adjusting one or more parameters of the linear controller based on an associated one or more parameters of the nonlinear model as the values of the measured variables move; further modifying the one or more parameters of the linear controller in a specified manner as the values of the measured variables move from the first operating region to the second operating region; the linear controller determining predicted control values for the manipulable variables in response to said further modifying; and outputting the predicted control values for the manipulable variables, wherein the predicted control values are useable to control the system.