Co-simulation of valve trains and timing drives including unilateral constraints and hydraulics

At the Institute of Applied Mechanics at the Technical University of Munich, Germany, several highly specialized and efficient computer programs have been developed to compute the dynamical behavior of complex gear drives and valve trains (Dynas), chain drives (KetSim) and hydraulic systems (HySim). A short overview of the simulation models of each program will be given. This work presents new simulation models of different valve train subsystems. The theory of unilateral and bilateral constraints in combination with set-valued force laws has been applied to the contact between cam and tappet. Moreover, a detailed valve spring model which uses the same approach is shown to be accurate. Hydraulic elements in the valve train are for example hydraulic lash adjusters. A modular simulation approach will be presented herefore. Finally, a co-simulation algorithm and its implementation to combine the computer programs is presented. The mathematical formulation of the co-simulation using different time-integration methods is introduced. Here, a time-stepping discretization in combination with an ODE-integrator with root-finding is used.