Management System for Continuously Variable Valve Lift Gasoline Engine 2007-01-1200
A continuously variable valve lift gasoline engine can improve fuel consumption by reducing pumping loss and increase maximum torque by optimizing valve lift and cam phase according to engine speed. In this research, a new control system to simultaneously ensure good driveability and low emissions was developed for this low fuel consumption, high power engine. New suction air management through a master-slave control made it possible to achieve low fuel consumption and good driveability. To regulate the idle speed, a new controller featuring a two-degree-of-freedom sliding-mode algorithm with cooperative control was designed. This controller can improve the stability of idle speed and achieve the idle operation with a lower engine speed. To reduce emissions during cold start condition, an ignition timing control was developed that combine I-P control with a sliding mode control algorithm. This enables the engine speed to reach the target value smoothly and promotes early activation of the catalytic converter. To reduce influence of disparities between individual cylinder air-fuel ratios, a new optimal control was designed using a sliding mode control mechanism with an expanded delta-sigma modulation algorithm. By applying this to secondary O2 feedback, the post-catalyst O2 sensor output can be controlled precisely and the catalytic conversion efficiency can be improved. Using these new technologies, simultaneous low emissions and good driveability were made possible without compromising the CVTL engine's unique advantages of low fuel consumption and high output.