Specifications

87
Why would anything in a smoothly running model behave like this? The answer lies in the ordinate axis. You
will notice that it has no values on it, and if you hold the mouse over a point on the curve a small window
will pop up and show you the value:
You can see that the value is 4.45e-14. For all practical purposes this is zero, and this is also why there are
no values on the ordinate axis. What you see here is really zero augmented by numerical round-off errors.
Final remarks
Notice that kinematic analysis determines velocities and accelerations in addition to positions. The position
analysis is by far the more challenging because the equations are nonlinear, whereas solution for velocity
and acceleration involves linear equations once the positions have been determined. Please notice also that
due to the very general approach used by the AnyBody Modeling System, it handles closed kinematic chains.
This is crucial in biomechanics where closed chains occur very frequently, for instance in bicycling, gait, and
whenever the model grabs something with both hands.
Although the kinematic analysis is useful in its own right for lots of purposes, it is also the first step of the
InverseDynamicAnalysis operation, the subject of the next lesson
.