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This paper proposes a new Electric Power Steering (EPS) control strategy that enables improvement to steering-wheel returnability. Using a conventional EPS controller, frictional loss torque in the steering mechanism reduces steering-wheel returnability, which drivers occasionally perceive as unpleasant. This phenomena occurs in any EPS system regardless of motor type or mounting location. To improve steering-wheel returnability for EPS-equipped vehicles, we developed a new control strategy based on estimation of alignment torque generated by tires and road surfaces. This proposed control strategy requires no supplemental sensors like steering-wheel angle or motor-angle sensors. We experimented with this proposed control algorithm using a test vehicle and confirmed that it enables improved steering wheel returnability and also better on-center feeling.

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 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.