@TechReport{	  it:2003-042,
  author	= {Gerardo Schneider},
  title		= {Invariance Kernels of Polygonal Differential Inclusions},
  institution	= {Department of Information Technology, Uppsala University},
  department	= {Division of Computer Systems},
  year		= {2003},
  number	= {2003-042},
  month		= aug,
  note		= {Updated October 2003},
  abstract	= {Polygonal hybrid systems are a subclass of planar hybrid
		  automata which can be represented by piecewise constant
		  differential inclusions (SPDIs). Here, we identify and
		  compute an important object of SPDIs' phase portrait,
		  namely \emph{invariance kernels}. An \emph{invariant set}
		  is a set of initial points of trajectories which keep
		  rotating in a cycle forever and the \emph{invariance
		  kernel} is the largest of such sets. We show that this
		  kernel is a non-convex polygon and we give a non-iterative
		  algorithm for computing the coordinates of its vertices and
		  edges.}
}