Energy and Passivity Based Control for Bipeds and Assistive Walking Devices

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2020-11-24

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Abstract

Locomotion is inherently an energy regulation challenge; ground impacts deplete the mechanical energy of the walking system with every step. When a person’s leg is amputated, one of the conventional medical devices used to help them recover their mobility is a passive prosthesis. However, this device is incapable of doing positive work on the human body to counteract energy depletion and restore the user’s mechanical energy. Powered prostheses have been developed and researched to address this, but recent control methods have focused on tracking joint trajectories or impedance while ignoring the fundamental kinetic aspect of human locomotion. The prevailing goal of this work is to construct a control method for a powered lower-limb prosthesis that explicitly and directly enhances the kinetics of the combined human-prosthesis system to assist human locomotion. The method proposed to accomplish this utilizes energy and passivity based control techniques to modify the dynamics of the prosthesis. This dissertation develops control theory related to these techniques for autonomous bipedal robots so that they can then be translated onto the target prosthesis system. Specifically, it shows how to use energy shaping and regulation to change characteristics of a walking gait, like walking speed, via switching of a small set of physically meaningful parameters. Experimental results that demonstrate proof-of-concept on a powered knee-ankle prosthetic leg are presented.

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Bipedalism, Nonlinear control theory, Passivity-based control, Artificial legs

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