ake sure that you take a minute to look at the code which runs during
      these examples.  Note the somewhat arbitrary threshold for switching to
      the balancing controller.  We'll give a much more satisfying answer for
      that in the <a href="lyapunov.html">chapter on Lyapunov methods</a>.</p>

      </example>

      <p>There are a few things that are extremely nice about this controller.
      Not only is it simple, but it is actually incredibly robust to errors we
      might have in our estima