Optimization of Spark Ignition Engines with Stochastic Effects in Sensors and Actuators

A dynamic model of a vehicle equipped with an electronic controlled spark ignition engine is presented. The model is used to simulate and optimize control strategies in transient conditions, both in case of deterministic or stochastic control system operation. Fuel consumption and emissions are evaluated starting from steady-state experimental data, considering also the effects on emissions of cylinder wall temperatures unsteadiness. The following dynamic phenomena are described in the model: unsteady air flow in the intake manifold, evaluated by a filling and emptying approach; two phases fuel flow, considering fuel evaporation, transport and deposition on walls; unsteady thermal flow between combustion chamber walls and cooling system. The model, characterized by limited computational time, is employed both in simulation and optimization mode to study control strategies for injection timing and spark advance, to compensate for mixture strength excursions and to improve dynamic performance, also considering stochastic effects exerted by random errors in sensors and actuators on air-fuel ratio and spark advance variance.