Internal Combustion Engine (ICE) Valve Train Modeling using Virtual Test Bed (VTB)

Daniel Sloope



Virtual Test Bed (VTB) is a real-time simulation environment that runs mathematical models.  A new camless engine is being designed by the Advanced Actuators Research Group.  To understand how the engine currently responds while the engine is running a mathematical model was written and then executed in VTB that showed valve train component position, velocity, and acceleration.  Figure 1 shows a schematic of the valve train that was modeled.


Figure 1. Overhead-Valve Valve Train


The basis of the mathematical model is a set of equations written in the User Defined Device (UDD) that relates each of the valve train componentsí mass, acceleration, velocity, position, stiffness, and damping constants.  UDD is a program related to VTB which generates C++ code so that VTB can understand it.  Once the model was written and the model was created the model was ran in VTB using different input parameters. Initially a sine wave was used to simulate the cam profile.  However, a cam profile program was also written and created in VTB.  Figure 2 is a schematic of the valve train and cam models in VTB.


Figure 2.  Valve Train Model Schematic


Simulation tests were run on the model.  Visual Extension Engine, a graphical program that accompanies VTB, shows the results of the model.  Figure 3 shows the graphical results of the model.



Figure 3.  Model Output, Position, Velocity, and Acceleration of Model



The valve train was based on an actual Honda GX31 engine.  To get accurate parameters for testing the model, the parts were modeled in ProEngineer.  Using ProE allows the user to get the moment of inertia which is then used to compute the stiffness and damping coefficients.  Having the correct constants will allow the model to be accurate.  Future work includes testing and verifying of the model.