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In this work we have developed an algorithm to estimate and control the air fuel ratio of each cylinder from the measurement of an UEGO sensor placed at the confluence point in the exhaust manifold. In our case of study the exhaust manifold was very asymmetric. We have developed a simple model of this exhaust manifold capable of satisfying the control objectives. The lambda value for each cylinder is predicted from the actual lambda value measured at the confluence point by 4 different static Kalman filters depending on the cylinder that has finished its exhaust phase. The lambda feedback uses the output of the Kalman filters to control the AFR for each cylinder. The algorithm has been implemented on a production SAGEM ECU and the experimental tests have been made on a PSA 1.8 liter 4 cylinder engine The experimental results show that the algorithm is able to correct the cylinder to cylinder AFR with an accuracy around 3% for a fueling variation of 30%.

This article describes an application of sliding mode techniques to the design of an air/fuel ratio control system for a 4-stroke engine, to minimize exhaust gas and emissions. This technique allows to achieve good control performance in terms of precision, robustness, and fast transient response. To support sliding mode control a second PI stage was added, based on the signal of a second oxygen sensor installed after the catalytic converter. Experimental results were better than those obtained with a conventional PI control, currently used on production applications. The new control algorithm (sliding mode based on the first oxygen sensor, and PI on the second) is very versatile because the approach chosen allows to calculate the parameters values for the ECU using computer simulation.

This paper describes an application of the H-infinity optimal control theory to the design of an engine idle speed electronic regulator. This technique, working directly on multi-input multi-output systems, allows to achieve optimal performances, good disturbances rejection and robustness to parametric variation of the plant. Compared to the current heuristic techniques for the tuning of the control parameters, the following procedure offers the opportunities to become completely automatic, reducing in this way time and efforts. The experimental results, finally, are better than those obtained by conventional P.I.D. regulators and equivalent of an optimal L.Q.I, ones.