Modeling of WalkMECH: A fully-passive energy-efficient transfemoral prosthesis prototype. - Ramazan Unal; F. Klijnstra; B. Burkink; S. M. Behrens; Edsko E. G. Hekman; Stefano Stramigioli; H. F. J. M. Koopman; Raffaella Carloni (ICORR, 2013)