On the use of a passive control mechanism to reduce impact phenomena in dual-magnet valve actuators for camless engine applications

The use of ElectroMechanical Valve Actuators (EMVAs) can offer many advantages of improving engine performance both in terms of increasing efficiency of combustion and reducing pollutant emissions. The EMVA adopted in this study is of the type with two opposed electromagnets and two counterbalanced springs. These actuators can suffer of valve impact phenomena during valve closing and opening manoeuvres. This is mainly due to strong non-linearities exhibited by electromagnetic force when air gap between armature and electromagnet rapidly decreases during the approaching of engine valve to its end-strokes. To cope with this problem the idea to include in the EMVA a small Hydraulic Damper (HD) to act as a passive control mechanism able to reduce the intensities of such impacts and so increasing lifespan of valve actuator. To this aim, we developed a detailed dynamic model of the EMVA, equipped with such velocity limiting mechanism, which was then used to carry out a wide numerical investigation of valve actuator behaviour. Finally, simulation data have been used for developing a control-oriented model which allows to conceive novel landing control algorithms relying on low cost sensors rather than using expensive wideband sensors for valve stroke measurement.