Flatness-based feedforward control of a two-stage turbocharged diesel air system with EGR

In this work, a nonlinear inversion-based feed-forward controller for a two-stage turbocharged diesel air system with exhaust-gas recirculation is developed. A nonlinear mathematical model is derived for the controller design on the basis of a high-order reference model by applying the singular perturbation theory. In this context, simplified models of different air system components are formulated in such a way that the resulting reduced-order model is differentially flat. Thereafter, the differential flatness property of the design model is exploited to derive the feedforward controller. The approximation performance of the reduced-order model as well as the suitability of the developed feedforward control scheme are finally evaluated by means of simulation studies.