A New Air-Fuel Ratio Feed Back Control for ULEV/SULEV Standard

A new A/F F/B control has been developed composed of two controls using one linear A/F sensor at the confluence point of exhaust gas to meet emission regulations such as the ULEV/SULEV. One control is individual cylinder A/F F/B control using the DFT algorithm with the linear A/F sensor at the confluence point. The other is confluence point A/F F/B control using the Smith Dead Time (SDT) controller. We discuss each A/F control and show results of their respective engine tests. These A/F F/B controls are integrated and, compared with conventional controls, show the good performance in the FTP mode test.