Foundations Of Cognitive Science

Passive Dynamic Walker

A passive dynamic walker is a walking device inspired by simple walking toys that were available in the 19th century. This type of walker is passive because it does not require motors or active mechanisms are to propel the device. Instead, gravity and inertia are all that are required. Passive dynamic walkers are usually placed on a gently sloping surface and walk down hill without additional power. They are of interest because their movement is clearly a walking movement. McGeer (1990a) provided a mathematical analysis that demonstrated that passive dynamic walking could be viewed as the rotation of a minimal wheel that consisted of a single spoke that served as a leg. He also created a straight-legged device that brought his mathematics to life. More advance passive dynamic walkers that have jointed legs have also been created and mathematically analyzed (Collins, Wisse & Ruina, 2001; McGeer, 1990b). Passive dynamic walkers are of interest to roboticists because humanoid robots expend a great deal of energy to generate walking gaits. Passive dynamic walkers point researchers in the direction of robots that walk, but do so with a much smaller expenditure of energy.


  1. Collins, S. H., Wisse, M., & Ruina, A. (2001). A three-dimensional passive-dynamic walking robot with two legs and knees. International Journal of Robotics Research, 20(7), 607-615.
  2. McGeer, T. (1990a). Passive dynamic walking. International Journal of Robotics Research, 9(2), 62-82.
  3. McGeer, T. (1990b). Passive walking with knees. Paper presented at the Proceedings of the IEEE International Conference On Robotics And Automation, Cincinnati OH.

(Added January 2010)