Design and Control of a Two-stage Electro-hydraulic Valve Actuation System

This paper discusses the design and control of a two-stage electro-hydraulic camless Variable Valve Actuation (VVA) system designed for gasoline engines that encompass a wide rpm range. The VVA portion of each engine valve assembly in the system consists of two miniature pilot valves, a proportional valve, a compound engine valve actuator and an engine valve return mechanism. The design and proper control of these devices allow for variable valve timing, lift, duration, seating velocity and flank velocity. This flexibility enables an array of combustion strategies. Many of these strategies (such as Miller cycle operation, cylinder and valve deactivation, etc.) have been tested on fired engines that have been redesigned to incorporate the VVA system. Test results for both bench and fired engines running in a dynamometer cell are presented. These results indicate the current level of controllability of the system and the power consumed by the system in a variety of test conditions.