Individual A/F Estimation and Control With the Fuel–Gas Ratio for Multicylinder IC Engines

In internal combustion engines with multicylinders, balancing the air-fuel ratio (A/F) for individual cylinders is an important issue for providing high-quality torque generation and reducing emissions. This paper addresses the individual A/F control problem for a six-cylinder engine with a single sensor. First, a modeling method to estimate the individual fuel-gas ratio, which immediately provides the A/F, is proposed, and using the estimation model, an adaptive generalized predictive control approach to balancing the individual cylinder characteristics is presented, which targets the static engine-operation mode. The effectiveness of the presented model is validated based on the experimental results, and a comparison with existing models is given based on the experiments. Finally, control performance with the proposed individual A/F control approach is demonstrated with the experiments conducted on a six-cylinder engine test bench.