Feedback linearization control for the air & charging system in a diesel engine

The air and charge subsystem of a diesel engine is a quite complex system with strong couplings, actuator constraints, and fast dynamics. MIMO model based control strategies are essential to deal with such a process. Furthermore, the air-path process is highly nonlinear, based on thermodynamical phenomena. Therefore, classical linear MIMO approaches are difficult to be applied and require system linearization over equilibrium operating points. Conversely, feedback linearization control can be applied smoothly. In this paper, an air and charging model-based multivariable control approach is described, which has been developed for a single-stage turbocharged diesel architecture, enabling an improved trade-off of NOx and PM (particulate matter) emissions and better transient performances. The developed approach uses a nonlinear physics-based model of the air and charging system, and the control architecture is based on the feedback linearization technique that decouples interactions and compensates nonlinearities. The nonlinear control is then coupled with PI controllers in order to guarantee the transient performances and robustness. Test-bench results show the effectiveness of the proposed approach.