Robust and stable locomotion over compliant terrains: application to lower-limb prostheses and bipedal robots
Date
2024
Authors
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Publisher
University of Delaware
Abstract
Over 2 million Americans are currently living with amputation, primarily of the lower limb. Although powered lower-limb prostheses manage to restore functional mobility and adapt to different speeds, conditions, and rigid terrains, no control strategy has been proposed so far to address walking over compliant terrains frequently encountered in everyday life. Similarly, despite significant advances in the design of bipedal robots, most existing control methodologies focus primarily on locomotion over rigid terrain. In real-world applications though, unforeseen compliant terrains are often encountered with highly variable ground properties. Therefore, in contrast to non-disabled humans who are considered the ``gold standard" of legged locomotion, consistent performance and safety cannot be guaranteed. As a result, the need emerges for a control methodology that enables stable locomotion over various compliant terrains. This dissertation proposes control strategies for achieving dynamic bipedal locomotion across various compliant surfaces. First, a novel model-based framework is proposed that allows the dynamic locomotion of bipeds across a wide range of compliant surfaces. Additionally, an admittance controller is proposed for powered ankle-foot prostheses to improve walking stability over various unilaterally and bilaterally compliant terrains. The results of this dissertation show that adjusting the quasi-stiffness of lower-limb prostheses and the leg stiffness of bipedal models allow for more effective, robust, and stable bipedal locomotion across various compliant terrains. As robust and stable walking over a wide range of compliant terrains is an important problem in legged locomotion, this work can significantly advance the field of bipedal walking by improving the control of bipedal robots and lower-limb prostheses. As a result, the performance of lower-limb prostheses could be significantly improved in daily activities, resulting in a better quality of life for people with lower-limb amputation. Similarly, bipedal robots could achieve high levels of versatility, reliability, and safety in real-world applications.
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Keywords
Bipedal locomotion, Compliant terrain, Stiffness, Walking stability, Lower-limb prostheses