1. Christian Albrechts University,Kiel,Germany
2. Graz University of Technology,Institute of Automation and Control,Christian Doppler Laboratory for Model-Based Control of Complex Test Bed Systems,Graz,Austria
3. Graz University of Technology,Institute of Automation and Control,Graz,Austria
4. Universidad Nacional Autonoma de Mexico,Instituto de Ingenieria,Mexico,D.F.