1. Department of Mechanical and Manufacturing Engineering; Aalborg University; Fibigerstraede 16 Aalborg East DK-9220 Denmark
2. Siemens Wind Power A/S; Assensvej 11 Aalborg East DK-9220 Denmark
3. AMADE, Polytechnic School; University of Girona; Campus Montilivi s/nGirona 17071 Spain