[IEEE 1997 IEEE/RSJ International Conference on Intelligent Robot and Systems. Innovative Robotics for Real-World Applications. IROS '97 - Grenoble, France (7-11 Sept. 1997)] Proceedings of the 1997 IEEE/RSJ International Conference on Intelligent Robot and Systems. Innovative Robotics for Real-World Applications. IROS '97 - Design of biped walking robots having antagonistic driven joints using nonlinear spring mechanism