accomplish control functions. Applying passive dynamics Adding actuation to passive dynamic walkers result in highly efficient robotic walkers. Such walkers can be implemented at lower mass and use less energy because they walk effectively with only a couple of motors. This combination results in a superior "specific cost of transport". Energy efficiency in level-ground transport is quantified in terms of the dimensionless "specific cost of transport", which is the amount of energy required to carry a unit weight a unit distance. Passive dynamic walkers such as the Cornell Efficient Biped have the same specific cost of transport as humans, 0.20. Not incidentally, passive dynamic walkers have human-like gaits. By comparison, Honda's biped ASIMO, which does not utilize the passive dynamics of its own limbs, has a specific cost of transport of 3.23. The current distance record for walking robots, 65.17 km, is held by the passive dynamics based Cornell Ranger. Passive dynamics have recently found a role in the design and control of prosthetics. Since passive dynamics provides the mathematical models of efficient motion, it is an appropriate avenue to develop efficient limbs that require less energy for amputees. Andrew Hansen, Steven Gard and others have done extensive research in developing better foot prosthetics by utilizing passive dynamics. Passive walking biped robots exhibit different kinds of chaotic behaviors e.g., bifurcation, intermittency and crisis. See also Underactuation References Bibliography and External links Cornell Biorobotics and Locomotion Lab — videos and papers on passive dynamic walkers, including McGeer's originals, the Cornell Efficient Walker, and the Cornell Ranger Droid Logic — simulations of passive dynamic walkers and runners created using evolutionary robotics MIT Leg Lab — walking and running robots that utilize natural dynamics Steve Collins' Robots page — the Cornell Efficient Walker, its passive predecessor, and additional references Robot kinematics 1980s in robotics