1. Austrian Center of Competence in Mechatronics GmbH (ACCM), Altenbergerstraße 69, A-4040 Linz, Austria e-mail:
2. Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, IA 52242 e-mail:
3. Department of Mechanical Engineering, Lappeenranta University of Technology, 53850 Lappeenranta, Finland e-mail: