© 1991 by Institute of Mathematics and its Applications
The Unmixing Problem
Institute for Dynamical Systems, University of Bremen P.O. Box 330 440, D-2800 Bremen, Germany bengt{at}mathematik.uni-Bremen.de
High-gain adaptive stabilization of minimum-phase linear systems raises the so-called unmixing problem: finding a finite set A of matrices, with the property that for any M
GL(n),
(AM)
C+ for at least one A
. First, some preliminary results will be given, leading up to a non-constructive proof of the existence of such finiteA's. For the cases n = 2 and 3, a fairly satisfying solution is presented. In higher dimensions, the situation is more complicated, and negative results are given. Based on the Euler angles for
O(n), an explicit solution is given for arbitrary n.