Maciejewski's Ill-Conditioned Equations of Motion paper

This paper shows how ill-conditioned motion can arise as a result of
solving kinematic equations, and gives a formula for approximating the
degree of severity in a given situation. They also present an overview 
of the problem itself. The problem is that for a given hierarchical 
model, some small positional motions require large angular changes (the 
so-called ill-conditioned problem). They don't solve the problem 
completely (it can't always be solved), but they show that by damping 
singular values, they can resolve discontinuities at a singularity.

Key ideas: By first identifying singularities, and then damping them,
smoother motion can be achieved.

Contributions: A well-conditioned IK solution. A formula for identifying
the condition number (worst-case bound on relative error) in a
transformation.