PERFORMANCE GAINS WITH EGR-FLOW INVERSION FOR HANDLING NON-LINEAR DYNAMIC EFFECTS IN EGR VGT CI ENGINES

A static non-linear compensator, that handles a sign reversal and a nonminimum phase behavior in diesel engines, is investigated. It inverts the EGR-flow model and is used in an inner loop in a control structure for coordinated control of EGR-fraction and oxygen/fuel ratio λO. An investigation of the advantages with the proposed non-linear compensator shows less overshoots in λO and less pumping work compared to a control structure without a non-linear compensator. Simulations also quantifies how much the control performance can be improved if an ideal EGR-actuator is used. The result is that the mean absolute EGR error can be reduced with 95%.