1. a Department of Electrical Engineering , Ohio State University , Columbus, OH, 43210, U.S.A.
2. b Automatic Control and Systems Analysis Group, Department of Technology , Uppsala University , Box 27, S-751 03, Uppsala, Sweden
3. c Automatic Control and Systems Analysis Group, Department of Technology , Uppsala University , Box 27, S-751 03, Uppsala, Sweden
4. d Automatic Control and Systems Analysis Group, Department of Technology , Uppsala University , Box, 27, S-751 03, Uppsala, Sweden