Modelling of an electro-hydraulic variable valve actuator for camless engines aimed at controlling valve lift parameters

This paper presents the mathematical modelling of an Electro-Hydraulic Valve Actuator (EHVA) prototype and its application to the design of cycle-by-cycle Valve Lift Control(VLC). EHVA is rated in the technical literature as an apparatus enabling Variable Valve Actuation (VVA) and implementation of advanced combustion concepts in future camless engines. It is, therefore, a first step towards the development of camless engines in which valve lift and timing can be freely adjusted valve-by-valve and cycle-by-cycle. Particular attention is paid to parameter identification aimed at obtaining a predictive simulation model of valve lift trajectories and valve parameters (e.g. lift, duration, area) for a wide range of system inputs. An energy loss assessment of a valvetrain based on EHVAs is described, and the results are compared with those obtained with a traditional cam-based valvetrain. The validated model is then used to build detailed numerical maps of valve parameters that are fundamental for setting up cycle-by-cycle controllers of valve parameters. Hence, the authors present the design of a cycle-by-cycle controller of maximum valve lift, the performance of which is tuned by simulations and then verified experimentally.