Effects of radial forcing on spring-mass running
Abstract
Previous work done with legged robots and above-the-knee amputees has shown that it is possible to achieve stable legged locomotion without an active ankle. If ankles are not required for legged locomotion, do they still provide some important function that cannot be produced without them? In this context, it is interesting to ask if and what helpful function the ankle can play in stable legged locomotion. This question can be extended to an investigation of stability of locomotion and designing experiments that can isolate and elucidate ankle function. While an active ankle can provide forcing both along the leg and perpendicular to it, perpendicular forcing has been investigated with previous models. Here the effects of radial forcing along the leg are studied by way of a simplified dynamic model of legged locomotion. The effects of these forces on stability and energetics are examined. The stability of this radially-forced model is examined and compared with a model powered by forcing perpendicular to the leg. The results of this demonstrate that the ankle plays a different role in legged locomotion than the hip, and that the stability offered by a radial forcing function is distinct from a stable hip-torqued model. Additionally, a prototype device is constructed to provide insight into exo-tendons. It consists of a torsion spring in parallel with the human ankle joint. Exo-tendons like this may assist in energy storage and release during the stance phase of the gait cycle. Revisions to the design are also suggested.
Degree
M.S.
Advisors
Seipel, Purdue University.
Subject Area
Mechanical engineering
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