Abstract
Fully flexible valve actuation (FFVA) systems, often referred to as camless valvetrain, employ electro-hydraulic or electro-magnetic actuators to drive the engine valves directly to achieve fully flexible valve motion. This paper presents the development and control of a laboratory electro-hydraulic fully flexible valve actuation (FFVA) system for internal combustion engines. System hardware includes servo valves, power amplifiers, hydraulic pump and cylinders, sensors and signal conditioners. They are integrated together and a robust tracking controller was designed and implemented to control the system. The FFVA system is able to generate real-time fully flexible motion for individual intake or exhaust valve and accommodate a large variety of valve profile strategies. Both bench test and combustion test were conducted to demonstrate the system´s flexibility and capability. In general, the developed electro-hydraulic valve actuation system can be used to explore the fuel economy and emission benefits of any valve-timing strategy. This includes, for example, cam phasing, two-step cam, variable valve lift, and variable valve lift and duration valve-timing strategies. It can also be used to investigate the performance of different advanced combustion concepts, such as homogeneous charge compression ignition (HCCI), low temperature diesel combustion etc..
Keywords: Camless engine, FFVA, HCCI, electro-hydraulic, motion control