We are running a vehicle shell model with additional lumped masses where needed attached to the shell structure. We achieve reasonable results, 6 rigid body modes followed by 20 modes that align with our other software tools. There is some discrepancy and we are not clear on whether displacement of the cg is occurring in modes 7-20. In the .pch file we are able to see the displacement of the mass elements as a result of each mode. Are those values real displacements, both positive and negative in a coordinate direction, or is there an imaginary component to the displacement? Is there a was to determine the motion of the CG of the system for each mode?
