1. Institute for Automation Engineering; Otto-von-Guericke University; Universitaetsplatz 2 Magdeburg 39106 Germany
2. Max Planck Institute for Dynamics of Complex Technical Systems; Magdeburg Germany
3. Laboratoire d'Automatique; École Polytechnique Fédérale de Lausanne; CH-1015 Lausanne Switzerland
4. Universtiy of Applied Science Biberach; Biberach Germany