Diesel Engine Cycle to Cycle Feed-forward plus Closed-loop Combustion Control

A model-based open-loop compensator has been combined with a cycle to cycle closed-loop controller with the aim of managing engine load and NOx (Nitrogen Oxides)emission. Both the control strategies employ a virtual sensor realized through a predictive combustion model calibrated on real test bench measurements. Thanks to the virtual sensor no direct in-cylinder pressure measurement is required. Injected fuel quantity and start of injection of the main pulse are regulated to target the desired engine load and NOx respectively. In the closed-loop control the regulation of the manipulated variables is performed by two separate loops implementing PI and lag regulators, one to control the engine load and the other the NOx. Both open-loop and closed-loop strategies have been tested separately and then in cooperation between them in order to improve the closed-loop controller time response. Model-in-the-Loop technique was exploited to develop and assess the three control strategies by co-simulation between Simulink and GT-Power executing a fast-running model of a light-duty FPT F1C Euro VI diesel engine. Simulations show promising results and real-time capacity, therefore the strategies are suitable for successive implementation on the real engine through rapid prototyping.