QUESTION: I have a multi-vehicle simulation. One of the vehicles is
stopped for a period and then begins moving again. While it is stopped,
the lateral acceleration output is a constant -0.4g throughout this period.
Despite this, the vehicle has no v velocity during this period. Could you help
me shed some light on this?
The issue is a classic example of
the need for non-zero termination velocities: When you set them to 0, the
equations of motion continue to be executed (because in discrete timestep
numerical integration, velocity will NEVER be exactly zero). So the simulation
is continuing to calculate tire forces, which happen to have a slip angle, which
says there’s a lateral force, which says there’s a lateral
acceleration.
To solve the problem, set the
Termination Linear and Angular velocities to an acceptably small value, say 0.1.
This will have ~nil effect on your analysis and makes the equations of motion
happy.