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With a view to application of model base development to exhaust catalyst design, a numerical model for catalytic reaction was formulated so as to be able to predict tailpipe emission during test mode running. In order to grasp the catalytic reaction characteristics, catalyst characteristics test using catalyst test pieces and synthetic gas was conducted and the basic reaction that takes place inside the exhaust catalyst was modeled by employing the 3 overall reaction models: Arrhenius model, competitive adsorption model, and adsorption model. By using the formulated numerical catalyst model, tailpipe emission estimation for a gasoline engine vehicle was carried out, and an estimated accuracy of within ±10% error range from the actual measurement was realized for all of CO, HC, and NO.

Recently, automotive emission regulations are being further tightened, such as the Tier III/LEV III in the U.S. As a result, reducing cost of after-treatment systems to meet these strict regulations has become an urgent issue, and then the demand for high-precision air-fuel ratio (A/F) control which can achieve this cost reduction is high [1]. On the other hand, in order to meet rapidly changing market needs, it is becoming difficult to keep enough development periods that enable sufficient calibration by trial-and-error, such as feedback-gain calibration. This leads to an increase in three-way catalytic converter costs in some cases. For these reasons, it is necessary to construct control system that can make full use of hardware capabilities, can shorten development periods regardless of the skill level of engineers.