Leg Stiffness and Articulated Leg Design for Dynamic Locomotion

A number of legged robots capable of dynamic running have been constructed, although, in most cases, very little explanation has been given for how the stiffness of the legs was selected. This paper proposes that a reasonable design value for a robot’s leg stiffness is the effective leg stiffness of an animal having the same mass. It further details a simple, kinetostatic analysis of articulated legs that can be used to determine the leg design geometry for a desired stiffness. The technique allows the designer to exploit the non-linearities in the leg mechanism to achieve an advantageous non-linear leg stiffness. An example of the method is given, and preliminary experimental results with the corresponding prototype leg are presented.