Study on Design Method of Combustion Reference Values for Model-Based Control of Advanced Diesel Engine

Model-based control systems are drawing attention in relation to implementing next-generation combustion technologies with high thermal efficiency and low emissions, such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) combustion, which have low robustness. A model-based control system derives control inputs according to reference values and operating conditions during every cycle and has potential to replace the conventional control map, which requires a large number of experiments. However, model-based control for engines requires reference values for combustion, such as heat release peak timing and heat release peak value; such values represent the combustion state. Therefore, the reference for the transient condition is important for utilizing the benefit of model-based control systems, given that such systems derive control outputs cycle by cycle. In this study, a design method for the combustion reference values for the transient operating condition is described for advanced diesel combustion, which uses premixed compression ignition combustion by multiple fuel injections. Specifically, a statistical method and a method based on model prediction considering the driving characteristics are proposed and compared in engine control experiments. These proposed methods were evaluated under defined simple transient operation conditions and worldwide harmonized light vehicles test cycles (WLTC) mode considering real road conditions. Results showed that designing the combustion reference values for transient operation by model prediction is effective, and such method has the potential to reflect the driving characteristics.