Internalmo del control of nonlinear systems described by velocity-based linearizations

Internal model control is applied to stable nonlinear systems described by linear parameter-varying models. Velocity-based linearizations are applied to construct a set of linearized models which provides a global description of the nonlinear system dynamics. The velocity-form linear parameter-varying system description gives an exact relation between the input and the output changes, while steady-state information is captured in an offset term. From the model structure it follows that an internal model controller based on the velocity-form linear parameter-varying model representation fails to eliminate steady-state offsets. In order to achieve a zero steady-state error when using velocity-based linearized models a modified internal model control structure is introduced. The proposed method is applied to a strongly nonlinear simulated pH neutralization process.