Initial conditions on joints

SDB666

Hi guys,

 

I would like to ask you why cannot I apply displacement initial conditions on joints? This happens for all kinds of joints, I can only apply velocity initial condition as shown in the figure below.

 

Thank you all.

 

 

Chris Coker_21312

In general, it's a better practice to apply your initial conditions to the Bodies, rather than the Joints.  In the real (non virtual) world, F=m * a.  The forces and accelerations act on the mass.  The joints add constraints to the degrees of freedom to the bodies.

 

Applying an initial displacement to a joint implies that you want an initial translation to occur immediately at time =0, because the joint is not initially in the desired location for the start of the simulation.  Numerically, this can lead to problems achieving a robust solution.

 

You can also apply a Motion to a Joint as a function of time if you need to move that joint to a particular position.  This is a more reliable way to position the joint, as you are applying an enforced displacement.

 

Chris