Stabilization methods for adaptive engine controls

The current engine systems to achieve extremely low emission has a wide range λ sensor positioned upstream of a catalyst and a switching λ sensor downstream. The system is required to maintain the output of the switching λ sensor to optimal target value under all engine load and catalyst aging conditions in order to optimize the conversion rate of catalyst. A standard STC (Self-Tuning Controller) and the robust adaptive controller composed of an identifier, a predictor and a sliding-mode controller are applied to the system at the beginning of this research. However, the standard STC caused the drift phenomena of adaptive parameters and could not provide sufficient control performance. The robust adaptive controller also caused the oscillation behavior of the output of the switching λ sensor. Consequently, the identification algorithms of two adaptive controllers are modified to avoid these issues. As a result, the control performance of the output of the switching λ sensor was dramatically improved and the emission from the engine controlled by the system was reduced to the level meeting LEV-II emission standard in California.