Dynamic steady-state allocation for over-actuated turbocharged diesel engines

This paper presents a control design for the air path system dynamics of a turbocharged Diesel engine equipped with exhaust gas recirculation (EGR), variable geometry turbine (VGT) and a variable geometry compressor (VGC) system. Previous work has shown that the VGC actuator provides the opportunity to improve the stability of the compressor, optimize its efficiency and increase the shaft speed to minimize the turbo lag during transients. Building upon this study, the extra degree of freedom introduced by the VGC is exploited in this paper to dynamically optimize some performance variables during transients while regulating the controlled variables to the desired set points. A linearized model, derived from a validated model of the engine air-path dynamics, is used for control design. The proposed control methodology, suitable for over-actuated systems, relies on the characterization of the redundancy in geometric terms. This redundancy is exploited to shape the steady-state response by optimizing on-line a given cost function. A case study that shows the effectiveness of the proposed control strategy is presented.