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We have developed an effective secondary air-injection system that reduces harmful substances such as HC and CO. The secondary air in this system is heated to 300°C and injected into the exhaust pipe. Though the temperature of the secondary air is relatively low, it can activate a three way catalyst more rapidly than conventional secondary air injection systems. Thus, in our system (a “Heated-Air-Injection System”) is expected to be very effective in reducing harmful substances in the cold transient phase of the US Federal Test Procedure. For designing the system and analyzing its performance, we developed a simulation model including the design parameters of the system, such as flow rate of heated air, heater power, and so on. Besides these design parameters, the model takes into account of heat transfer from exhaust gas to exhaust pipe, gas-conversion reactions in a three way catalyst, and heat transfer efficiency of the electric heater.

A robust cruise control system using a disturbance observer is proposed. A control design method based on the two-degree-of-freedom (2-DOF) control including a disturbance observer is introduced. The proposed controller provides that: (1) input command responses are not affected by driving condition, such as vehicle speed, and road gradient (2) input command response and disturbance suppression performance can be designed independently (3) choice of an appropriate parameter value in the disturbance observer depending on the throttle opening gives a proper trade-off between the robust performance and the robust stability over a wide driving range. Simulation and experimental results show that the proposed system is robust against both parameter variations and disturbances.

A fuel control method to reduce the harmful exhaust gas from SI engines is proposed. As is well known, both the amplitude and the frequency of the limit cycle in a conventional air-fuel ratio control system are determined uniquely by parameters in the system. And this limits our making full use of the oxygen storage effect of TWC. A simple model of TWC reaction revealed the relationship between maximum conversion efficiency and both the amplitude and the frequency in a air fuel control system. It also revealed that TWC conversion efficiency attained to maximum levels when both the amplitude and the frequency of the limit cycle are selected so as to make full use of the oxygen storage effect of TWC. In order to achieve this, it is necessary to vary both the amplitude and the frequency arbitrarily.

It is well-known that decreasing idle speeds is one of the ways to reduce fuel consumption. On the other hand, it is also well-known that even slight fluctuations of the idle speed cause unpleasant vibrations of the vehicle when this speed is set at low values. Therefore, it is important to create idle-speed control (ISC) systems that undergo less idle-speed fluctuations with respect to various load disturbances, in order to reduce fuel consumption without giving rise to unpleasant vibrations. The first topic of this paper is a linearized model which derives a new feedforward compensation method for reducing idle-speed fluctuations caused by load distrubances for specific electric loads. The second concerns the control results of our ISC system using this feedforward compensation. The final topic is a discussion of the validity of the parameter values used in the feedforward compensation.

A control strategy for reducing transient Air/Fuel ratio excursions for improvements of transient engine responses is proposed through investigations of the various factors which affect transient A/F control results. First, a large number of controlled parameters in transient A/F control such as fuel transport delay, injection timing, the static flow rate of injectors, sensing delay of the air flow rate etc. are discussed through analyzing the behaviors of both the indicated mean effective pressure Pi and A/F in various transient situations. In particular, the influence of injected fuel atomization is investigated with a visualization technique using an actually operating engine equipped with a visual manifold. Then, a transient engine dynamics is formulated, taking into account the above controlled factors. Applicability of the dynamics to transient A/F control strategies is discussed.