Propulsive Characteristics of Rotary Force and Its Influence on Bipedal Gait Initiation and Gait Transition Speed
Abstract
This dissertation explores the role of rotational leg force in human locomotion as an actuation strategy for common locomotion tasks including walking and running at different speeds, reaching high speed walking limits, and initiating walking gaits. First, the rotary component of the ground reaction force (acting perpendicular to the leg) is investigated experimentally for both walking and running. The results suggest that the rotary component of leg force provides a propulsive contribution to the forward motion of body mass center: rotary force has significant magnitude (peak values from 5% to 38% of body weight, from slow walking to moderate running respectively) and its power contribution to mass center motion is positive and changes with positive correlation to speed. Second, the influence of rotary leg forcing on the speed of walking and mechanical limits to walking speed is studied using a theoretical analysis based on an actuated bipedal spring-loaded inverted pendulum model. Compared to previous locomotion models without rotary actuation, the predicted mechanical limits of walking speed are found to occur closer to the experimentally-observed range of preferred transitions speed (~2.0 m/s), suggesting that the mechanics of locomotion with rotary actuation could be a factor involved in preferred gait transition. Finally, a strategy for regulating rotary leg force during gait initiation is studied using the same actuated spring-loaded inverted pendulum modeling framework, but extended to include representation of anticipatory postural adjustments. A sublinear relationship between the rotary leg force used at each step and the velocity error (with steady state speed) was found to predict the velocity progression observed in experiments. Absence of anticipatory postural adjustments increased step lengths and rotary leg force in the model, making initiation more challenging.
Degree
Ph.D.
Advisors
Seipel, Purdue University.
Subject Area
Mechanical engineering|Biomechanics
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