Space Grant Consortium - University of Wisconsin - Green Bay

Figure 1. Assembled hydraulic excavator model as seen in MSC/ADAMS
New Computational Model. Work was then done on replicating the MSC/ADAMS track
model so it could be used by ChronoEngine. ChronoEngine is a research-grade dynamics engine
which has no graphical user interface, unlike MSC/ADAMS which allows users to see and
visually inspect models as they are created. There are classes implemented in the program which
allow the user to write programs that model and simulate multibody systems. Functions were
written using a C++ programming environment so that the rigid body information and kinematic
constraints for the tracked vehicle model were identical in ChronoEngine and MSC/ADAMS.
Rigid body frictional contacts using the new formulation were created between the track shoes
and all the other bodies in the system. However, problems were encountered when attempting to
create collision objects for the complex geometry in the model. More accurate collision objects
were created by substituting a set of convex hulls for each rigid body collision object, also
known as convex decomposition, which is discussed in the next section.
Convex Decomposition. In the early stages of testing the track model using ChronoEngine, it
became apparent that the program lacked the ability to represent complex geometry correctly as
collision objects. There are only two types of bodies that have complex geometry in the model,
the track shoes and the gears of the drive sprocket. Figure 2 shows a Computer-Aided Design
(CAD) representation of the excavator track shoe.
20