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The purpose of this study is to develop control-oriented modeling methodology and apply to an actual control design in turbocharged spark ignition engines. A grey-box modeling approach was adapted to accelerate the system calibration time, while providing accurate system dynamics. An engine simulator based on first principles models was utilized to investigate the statistical model derivation process. A recursive least squares method with forgetting factor was employed to estimate model parameters related to turbocharger and vehicle/drivetrain behaviors, which seemed to be major factors causing delay of turbocharger system. The concept was demonstrated through its application to the actual control design, and the reliability of the proposed method was theoretically investigated. According to the model evaluation results, approximated behavior models are in good agreement with time series data yielded by the engine simulator under various transient operations.

For compliance with the exhaust emission regulations, such as SULEV and STAGE4, a new air-fuel ratio control system has been developed. The concept behind this system is that the best performance of air-fuel ratio control is achieved with the minimum of man-hours of adaptation. The system consists of a section in which an engine's air-fuel ratio is fed back and a section in which the amount of oxygen stored by the catalyst is predicted and controlled. In the feedback section, a high-precision air-fuel ratio control was achieved. In the oxygen storage mass predicting and controlling section, a catalyst model was incorporated to predict the amount of oxygen in the catalyst. The important point to note in this control system is that the air-fuel ratio feedback section requires no adaptation work when using an actual engine.

We have applied a non–linear control system to a hydraulically–operated continuous valve timing control (C–VTC) now in the mainstream of variable valve actuation systems. The system applied this time is a sliding mode control (SMC), which is found of late in a number of applications. Hydraulic pressure serving as the driving source of the C–VTC and the mechanism of the C–VTC have non–linear characteristics. We have investigated certain problems which occur, influenced by this non–linearity, when using a PID controller for C–VTC control. Typical issues include a large program memory size because of the large number of control parameters, a resultant considerable number of man–hours required for adaptation, and the low compatibility of response performance both for large step operations and for small step operations. Furthermore, high machining accuracy is required for the mechanical components.

Control of internal combustion engines depends on reduced idle speed and stabilized idling to improve fuel consumption.. Using a valve (ISC/V) to adjust air intake at idling, various idle speed control techniques have been proposed to improve response to variations in the target idle speed due to disturbance and to enhance speed control stability. Many conventional idle speed control systems utilize P and I control. They cannot compensate for the phase difference caused by the intake air volume between the throttle and intake valves. This leads to poor response to variations in the target idle speed and unsatisfactory control accuracy, that is, problems in preventing engine stalling and maintaining idle speed stability. To solve these problems, an idle speed control system based on fuzzy control(1)* theory is proposed. However, it is impossible to determine the control constant (membership function) theoretically.