Graduation Year


Document Type




Degree Granting Department

Mechanical Engineering

Major Professor

Kyle Reed, Ph.D.

Committee Member

Rajiv Dubey, Ph.D.

Committee Member

Jose Porteiro, Ph.D.


Bipedal, Four-legged, Robot, Prosthesis, Gait Rehabilitation


Recent interest in using passive dynamic walkers (PDWs) for gait rehabilitation studies has presented a need for a robust, easily built mechanism. Unfortunately, these passive robots are hypersensitive to many variables outside of the usual design considerations that are studied when constructing them. By accentuating previous failures instead of suppressing them, this thesis presents a number of problematic situations commonly experienced when testing and tuning a PDW.

Further, through a complete design of a 4-legged PDW with knees, simple design axioms brought about by myself and others are put into a practical context and applied directly to design. This thesis aspires to present a systematic design process, and highlight how a computational model can be used with both hand calculations and CAD packages. Using the insight from those researchers before me, I strive to further their designs and present relevant information in a design compendium that makes it more useful to those who have an application for the device.

This thesis resulted in two novel designs for a PDW. First, a changing radius foot was developed to increase knee flexion upon toe off. The decrease in radius increases joint angular velocity resulting in ramp up. Further investigation of these feet could result

in more stable and efficient walking patterns. The other design brought to attention is the planar crossbar mechanism for coupling the inner and outer legs. The crossbar provides a rigid coupling without changing the rotational inertia between the coupled pair about the hip axis.