2009

the motion of a child part according to a parent part through the degree of
freedom (DOF) of the joint that links them. As a result, select the initial velocity
of a degree of freedom carefully.
Coherent Masses and Inertia
Ensure that the mechanism is well-conditioned. For example, the mass and
inertia of the mechanism should be in the same order of magnitude. The most
common error is a bad definition of density or volume of the CAD parts.
Continuity of Laws
Numerical computing is sensitive toward incontinuities in imposed laws. Thus,
while a velocity law defines a series of linear ramps, the acceleration is
necessarily discontinuous. Similarly, when using contact joints, it is better to
avoid profiles or outlines with straight edges.
NOTE Using little fillets eases the computation by breaking the edge.
48 | Chapter 7 Get Started with Simulation