Eigenstructure assignment by output feedback

The eigenstructure assignment using state variable feedback is analysed. It is interesting to examine the extent of eigenstructure assign ment that is possible if only output feedback is employed (number of outputs less than the number of states). At the outset, the pole placement problem with output feedback has received much attention by researchers over the years. In the state feedback case, all system poles can be arbitrarily assigned if the system is controllable. Unfortunately such a definitive statement in case of output feed back continues to be elusive.