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In modern Diesel engines Exhaust Gas Recirculation (EGR) and Variable Geometry Turbochargers (VGT) have been introduced to meet the new emission requirements. A control structure that coordinates and handles emission limits and low fuel consumption has been developed. This controller has a set of PID controllers with parameters that need to be tuned. To be able to achieve good performance, an optimization based tuning method is developed and tested. In the optimization the control objectives are captured by a cost function. To aid the tuning a systematic method has been developed for selecting representative and significant transients that excite different modes in the controller. The performance is evaluated on the European Transient Cycle. It is demonstrated how weighting factors in the cost function influence control behavior, and that the proposed tuning method gives a significant improvement in control performance compared to standardized tuning methods for PID controllers.

One important area of SI-engine diagnosis is the diagnosis of leakage in the air-intake system. This is because a leakage can cause increased emissions and drivability problems. A method for accurately detecting leaks is presented. The results are developed for a turbo-charged engine but they are also valid for a naturally aspirated SI-engine. The method is based on a physical model of the leaks and includes an estimation of leakage area. By knowing the area, it is possible to reconfigure the control algorithm such that, the effect of the leak on emissions, is suppressed. As small leaks as 2 mm in diameter can be detected and it is possible to distinguish between leakages before or after the throttle. The method is suitable for on-line implementation.

The main result of this paper is a real-time closed loop demonstration of spark advance control by interpretation of ionization current signals. The advantages of such a system is quantified. The ionization current, obtained by using the spark plug as a sensor, is rich on information, but the signal is also complex. A key step in our method is to use parameterized functions to describe the ionization current [1]. The results are validated on a SAAB 2.3 1, normally aspirated, production engine, showing that the placement of the pressure trace relative to TDC is controlled using only the ionization current for feedback.

Because of legislative regulations like OBDII, on-board diagnosis has gained much interest lately. A model based approach is suggested for the diagnosis of the air intake system of an SI-engine. Important research issues are modeling concepts, residual generation and evaluation, overall performance, and limiting factors. The diagnosis system is based on a non-linear semi-physical model and uses a combination of different residual generation methods. It is capable of detecting and isolating faults in the throttle actuator, throttle sensor, air mass now sensor and manifold pressure sensor. The scheme is experimentally validated on a real production engine.