Cycle to cycle closed-loop combustion control through virtual sensor in a diesel engine

A cycle to cycle closed-loop combustion controller for the management of engine load and NOx (Nitrogen Oxides) emission has been developed and tested for the light-duty FPT F1C Euro VI diesel engine. The closed loop controller exploits the feedback coming from a predictive combustion model used as a virtual sensor and calibrated on real test bench measurements. Thanks to the virtual sensor no direct in cylinder pressure measurement is required. The control system is composed by two separate loops implementing PI and lag regulators, one to control the engine load and the other the NOx. These two quantities are regulated through the correction of the main injected fuel quantity and the start of injection respectively. Nominal values for the two command actions are retrieved from steady state maps, so adding a feed-forward action. Each cylinder is controlled separately so that, in total for the 4 cylinders engine, 8 regulators are used. All the tests necessary to tune the regulators were carried out on the mono-dimensional simulation software GT-Power by Gamma Technologies that has proven to be very effective. The GT power model was also used for the assessment of the controllers: simulations show very encouraging results also in presence of high disturbances on the outputs.