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4. Powered hip exoskeleton improves walking economy in individuals with above-knee amputation

Author

Ishmael, Marshall K., Archangeli, Dante, and Lenzi, Tommaso

Subjects
Ambulation aids -- Innovations, Prosthesis -- Complications and side effects -- Patient outcomes, Implants, Artificial -- Complications and side effects -- Patient outcomes, Amputation -- Complications and side effects -- Patient outcomes, Biological sciences, Health
Abstract

Above-knee amputation severely reduces the mobility and quality of life of millions of individuals. Walking with available leg prostheses is highly inefficient, and poor walking economy is a major problem limiting mobility. Here we show that an autonomous powered hip exoskeleton assisting the residual limb significantly improves metabolic walking economy by 15.6 [plus or minus] 2.9% (mean [plus or minus] s.e.m.; two-tailed paired t-test, P = 0.002) in six individuals with above-knee amputation walking on a treadmill. The observed metabolic cost improvement is equivalent to removing a 12-kg backpack from a nonamputee individual. All participants were able to walk overground with the exoskeleton, including starting and stopping, without notable changes in gait balance or stability. This study shows that assistance of the user's residual limb with a powered hip exoskeleton is a viable solution for improving amputee walking economy. By significantly reducing the metabolic cost of walking, the proposed hip exoskeleton may have a considerable positive impact on mobility, improving the quality of life of individuals with above-knee amputations. In individuals with above-knee amputation, a powered hip exoskeleton, which reduces the metabolic cost of walking by adding energy at the hip joint, greatly improves walking economy and has the potential to improve mobility., Author(s): Marshall K. Ishmael [sup.1] , Dante Archangeli [sup.1] , Tommaso Lenzi [sup.1] Author Affiliations: (1) Department of Mechanical Engineering and Robotics Center, University of Utah, Salt Lake City, USA [...]

Published
2021
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11. Continuous A-Mode Ultrasound-Based Prediction of Transfemoral Amputee Prosthesis Kinematics Across Different Ambulation Tasks

Author

Mendez, Joel, Murray, Rosemarie, Gabert, Lukas, Fey, Nicholas P., Liu, Honghai, and Lenzi, Tommaso

Abstract

Objective: Volitional control systems for powered prostheses require the detection of user intent to operate in real life scenarios. Ambulation mode classification has been proposed to address this issue. However, these approaches introduce discrete labels to the otherwise continuous task that is ambulation. An alternative approach is to provide users with direct, voluntary control of the powered prosthesis motion. Surface electromyography (EMG) sensors have been proposed for this task, but poor signal-to-noise ratios and crosstalk from neighboring muscles limit performance. B-mode ultrasound can address some of these issues at the cost of reduced clinical viability due to the substantial increase in size, weight, and cost. Thus, there is an unmet need for a lightweight, portable neural system that can effectively detect the movement intention of individuals with lower-limb amputation. Methods: In this study, we show that a small and lightweight A-mode ultrasound system can continuously predict prosthesis joint kinematics in seven individuals with transfemoral amputation across different ambulation tasks. Features from the A-mode ultrasound signals were mapped to the user's prosthesis kinematics via an artificial neural network. Results: Predictions on testing ambulation circuit trials resulted in a mean normalized RMSE across different ambulation modes of 8.7 ± 3.1%, 4.6 ± 2.5%, 7.2 ± 1.8%, and 4.6 ± 2.4% for knee position, knee velocity, ankle position, and ankle velocity, respectively. Conclusion and Significance: This study lays the foundation for future applications of A-mode ultrasound for volitional control of powered prostheses during a variety of daily ambulation tasks.

Published
2024
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12. Neuro-robotics Paradigm for Intelligent Assistive Technologies

Author

Vitiello, Nicola, Oddo, Calogero Maria, Lenzi, Tommaso, Roccella, Stefano, Beccai, Lucia, Vecchi, Fabrizio, Carrozza, Maria Chiara, Dario, Paolo, Siciliano, Bruno, Series editor, Khatib, Oussama, Series editor, Mohammed, Samer, editor, Moreno, Juan C., editor, Kong, Kyoungchul, editor, and Amirat, Yacine, editor

Published
2015
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43. Indirect Volitional Swing Control Allows for Level-ground Walking and Crossing over Obstacles with a Powered Knee and Ankle Prosthesis

Author

Mendez, Joel, Hood, Sarah, Gunnel, Andy, and Lenzi, Tommaso

Subjects
Knee Joint, Joint Prosthesis, Artificial Limbs, Walking, Prosthesis Design, Models, Biological, Article, Biomechanical Phenomena, Amputees, Humans, Computer Simulation, Range of Motion, Articular, Knee Prosthesis, Gait, Ankle Joint
Abstract

Powered prostheses aim to mimic the missing biological limb with controllers that are finely tuned to replicate the nominal gait pattern of non-amputee individuals. Unfortunately, this control approach poses a problem with real-world ambulation, which includes tasks such as crossing over obstacles, where the prosthesis trajectory must be modified to provide adequate foot clearance and ensure timely foot placement. Here, we show an indirect volitional control approach that enables prosthesis users to walk at different speeds while smoothly and continuously crossing over obstacles of different sizes without explicit classification of the environment. At the high level, the proposed controller relies on a heuristic algorithm to continuously change the maximum knee flexion angle and the swing duration in harmony with the user's residual limb. At the low level, minimum-jerk planning is used to continuously adapt the swing trajectory while maximizing smoothness. Experiments with three individuals with above-knee amputation show that the proposed control approach allows for volitional control of foot clearance, which is necessary to negotiate environmental barriers. Our study suggests that a powered prosthesis controller with intrinsic, volitional adaptability may provide prosthesis users with functionality that is not currently available, facilitating real-world ambulation.

Published
2020

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