Coordinated Performance Optimization of a Variable Geometry Compressor With Model Predictive Control for a Turbocharged Diesel Engine

The concept of variable geometry compressor (VGC) has been recently proposed as a future improvement for automotive turbochargers to further increase the efficiency and boosting at low engine speed, and to provide a more direct control over the stability margin at medium-high engine load. This paper presents a control design for the air path system of an automotive diesel engine equipped with exhaust gas recirculation (EGR), variable geometry turbine (VGT), and VGC systems. Starting from a validated model, a study of the steady-state and dynamic responses is conducted to understand the influence of the VGC combined with VGT-EGR actuators on the performance of the system. Then, a feedback control strategy that coordinates the VGC actuator with the existing VGT-EGR controller based on model predictive control is proposed to optimize the compressor performance. The new methodology shows how the VGC can be used to increase the stability range of the compressor while providing the opportunity to improve its efficiency, by means of shifting the surge limit and reshaping the peak efficiency region of the machine. Simulation results on a vehicle acceleration profile with gear shift transients are provided to verify the effectiveness of the proposed methodology.