Preliminary results of cycle-by-cycle control of timing and lift of engine valve actuated through an electro-hydraulic VVA system

Intake and exhaust valves in Internal Combustion Engines (ICEs) are traditionally actuated by means of fixed cam-based mechanisms that allow to implement just one valve lift profile for all engine operating conditions. Instead, the possibility to introduce flexibility in varying valve lift parameters, such as valve timing and/or maximum valve lift position, has been widely investigated as an effective technique to improve more and more the efficiency of ICEs and as consequence reducing fuel consumptions. In this regard different Variable Valve Actuation (VVA) technologies have been developed and nowadays adopted in modern ICEs although most of them are still based on camshaft. This is a first step ahead towards the development of future camless engines where valve lift and timing could be adjusted freely from valve to valve. In this scenario we have focussed studies on a prototype of Electro-Hydraulic Valve Actuator (EHVA) proposed as an enabling VVA technology for implementing advanced combustion concepts in future camless engines. Unfortunatley, each EHVA system needs to be properly managed to be able to vary opening duration and lift of engine valve actuated by it. To this aim, we present a preliminary design of a cycle-by-cycle controller aimed at regulating such valve parameters. The proposed control strategy relies on two controllers operating separately for regulating the opening duration and lift of an engine valve. The performance of cycle-by-cycle controller are evaluated through simulations and numerical results presented.