Control and Controllability of Electrohydraulic Valvetrain in High and Medium Speed Diesels 2002-01-2175

An electrohydraulic valvetrain for experimental engine, having power density twice the level of current production engines, has been developed by the Institute of Hydraulics and Automation of Tampere University of Technology. Valvetrain offers significant benefits in comparison to traditional cam actuated valvetrain to control of the engine and also to general engine design.

Applying an electrohydraulic subsystem for valve actuation into the engine, having speed range up to 1600 rpm and combustion pressure range up to 400 bar, sets speed and controllability requirements of the electrohydraulic system to very unusual level. Hydraulic system peak power of approx. 100 kW and the nominal actuation time of 6 ms make hydraulic component and both hydraulic and control system design very different from traditional hydraulic systems. Delays caused by single hydraulic components and hydraulic volumes as well as dynamics of them have much more significant effects on the performance of the complete system than in traditional hydraulic systems. Speed of the system also makes it impossible to utilize control strategies usually used in electrohydraulic systems but a completely new approach is needed.

The paper will give an indepth introduction to valvetrain and its control system design. Simulation models used in design, hardware-in-the-loop models for testing the control system and combined Amesim hydraulics model / Simulink control system model are discussed. Also the final valvetrain construction and dSpace control system are introduced.