Abstract
Common rail diesel engines are widely employed for the research and the development of the advanced compression-ignition (CI) combustions which includes premixed charge compressionignition (PCCI) and low temperature combustion (LTC). In these combustion systems, flexibilities on the control of injection pressure are required. Fuel spray atomization and engine emission can be benefited from the high injection pressure which is much higher than in normal CI applications. These combustion systems can deliver both high efficiencies and very low emissions. However they are currently not capable to cover the whole load and speed range of the engine. Therefore, a special operating condition which requires a large step change of the rail pressure setpoint is accordingly needed while switching between and advanced CI combustion and the normal CI combustion. This condition is not existed in traditional diesel engine management systems. Traditional control strategy utilizing PID controller is difficult to fulfill the requirement of fast transient response of rail pressure in the control of the combustion mode switching. Therefore an advanced model-based controller is developed. By combining the feed-forward common rail model including injector, rail, pump and the ECU (Engine Control Unit) driver models with the modules of leak compensation control and the control quality monitoring module, this model-based controller (MBC) has not only the advantages of traditional PID controller but also the improved features of fast response, no overshoot and easy calibration. Experiments show that MBC can improve the control performance in engine transient and is able to assure the system safety. This controller has been practically applied in the development of engine management system for a prototype of the advanced CI diesel engine.
Keywords: Advanced Compression-ignition, Common Rail, Model-based Control, Control Quality Monitoring