Air path sensors are affected foremost by any faulty conditions caused by the valve actuators. Hence, they are chosen as the focus of this study and are analyzed for the first time for such an application. The hot film mass air flow sensor is studied for its precision at dethrottled operation at low loads which is not within the typical sensor operating range. The capability of this sensor to deduce the cylinder-individual air charge information is also investigated by using a rectangular signal windowing method. The hot film mass air flow sensor is found to be useful for dethrottled engine operation with variable valve systems. On the other hand it is proven to have slow response for fully variable valve application where each cylinder can be controlled separately. Furtherrnore, a new signal model is proposed for the manifold pressure for steadystate conditions. The signal model uses only a few barmonics of the Fourier series. Contrary to existing efforts, it works in tbe time domain, thereby using the information of occurrence times to isolate faults between the intake and exhaust actuators. The modeling issues such as synchronization of the model with the sensor data and adaptive threshold for residual data are handled. The results of these studies are supported by measurements taken on a four-cylinder gasoline Audi EA 113 test bench engine equipped with an electro-hydraulic valve system for both intake and exhaust. The method is found to detect and isolate the emission-critical faults of fully variable valve actuators, and is thus recommended to fulfill tbe on-board diagnostics (OBD) requirements.
On-board diagnostics of fully variable valve actuator systems in spark-ignited combustion engines
2010
176 Seiten, 124 Bilder, 24 Tabellen
Hochschulschrift
Deutsch
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