Flatness-Based Control of Mode Transitions Between Conventional and Premixed Charge Compression Ignition on a Modern Diesel Engine With Variable Valve Actuation

Energy needs in the transportation sector and strict emissions regulations have caused a growing focus on increasing engine efficiency while simultaneously minimizing engine out emissions. One method for accomplishing this is to leverage advanced combustion strategies which are efficient yet very clean. One such combustion mode is premixed charge compression ignition (PCCI). PCCI can lead to drastically lower emissions than conventional diesel combustion while still maintaining engine efficiencies; however, the engine operation region over which it can be utilized is limited. In order to take advantage of this advanced combustion mode, engines must be designed to move between conventional diesel combustion and PCCI. To achieve transitions between different combustion modes, a control strategy was developed which utilizes a extensively validated gas exchange model and flatness-based methods for trajectory planning and trajectory tracking to enable smooth transitions between different combustion modes on a modern diesel engine with variable valve actuation. Since the engine considered here has the ability to alter valve timings, the control method exploits both capabilities to control the gas exchange process as well as the effective compression ratio of the engine. Simulation results indicate that this flatness-based approach is effective in enabling mode transitions.