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For global environmental protection and resource conservation, Honda has developed a low precious-metal perovskite catalyst system in response to LEV-II, which achieves both low emissions and a reduction in the amount of precious metal used. The amount of precious metals used in the catalyst, per vehicle, is expected to be 50% less than in conventional systems. This system is comprised of an air-fuel ratio control system based on Honda's unique high-accuracy air-fuel control system, combined with a perovskite catalyst jointly developed with the US Company CSI. This system's performance is expected to reach the levels required by LEV-II regulations. Perovskite is a mix-metal oxide material that is widely used in general applications other than catalysts. However, it has not been widely used in automobile catalysts, because, in comparison with precious-metal catalysts, both the heat resistance and conversion efficiency during the warm-up process is reduced.

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.