[1] Univ Zaragoza, Dept Ingn Mecan, C Maria Luna S-N, Zaragoza 50018, Spain
[2] Lecitrailer SA, Camino Huertos S-N, Zaragoza 50620, Spain
[3] Univ Politecn Madrid, INSIA, Campus UPM,Carretera Valencia A-3,Km7, Madrid 28031, Spain
[4] Univ Oviedo, Escuela Politecn Ingn Gijon, Campus Gijon S-N, Gijon 33203, Spain