Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis
The prevalence of major lower limb loss in the United States is projected to increase significantly due to rising rates of diabetes and obesity, highlighting an urgent need for advanced prosthetic solutions [1]. Individuals with lower limb amputations often face increased energy expenditure and seco...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2025
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| Online Access: | https://hdl.handle.net/1721.1/158319 |
| _version_ | 1826212836783685632 |
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| author | Du, Lucy W. |
| author2 | Herr, Hugh M. |
| author_facet | Herr, Hugh M. Du, Lucy W. |
| author_sort | Du, Lucy W. |
| collection | MIT |
| description | The prevalence of major lower limb loss in the United States is projected to increase significantly due to rising rates of diabetes and obesity, highlighting an urgent need for advanced prosthetic solutions [1]. Individuals with lower limb amputations often face increased energy expenditure and secondary musculoskeletal conditions as a result of using conventional prosthetic devices [2]. These challenges underscore the necessity for innovative prosthetic designs that can enhance user mobility and comfort. A promising prosthesis solution are powered ankle-foot prostheses, which have the potential to provide biologically accurate push-off power, thereby offering significant benefits such as improved walking economy, increased mobility, and reduced impact forces on the user’s residual limb. However, existing powered prostheses often lack customization and fail to adequately meet the diverse and specific needs of individual users, which can limit their effectiveness and adoption. This thesis introduces a personalized, optimized, low-profile powered ankle-foot prosthesis, known as the Cycloidal Ankle (CyAn), designed to achieve biological ranges of motion and torque during level-ground walking. The CyAn employs a cycloidal drive transmission and a series carbon fiber spring to mimic tendon-like compliance, which enhances energy storage and return while maintaining a low build height to accommodate a broader range of users. The prosthesis device is capable of 25◦ of dorsiflexion and 41◦ of plantarflexion, and is capable of outputting at least 130 Nm of torque during walking, corresponding to biological ankle torque during level ground walking at 1.5 m/s for a 50th percentile male [3]. The CyAn prosthesis uses of a cycloidal drive transmission coupled with a series carbon fiber spring. This combination replicates tendon-like compliance and allows for a reduced build height without compromising the prosthesis’s range of motion or mechanical performance. The development of the CyAn prosthesis involved a comprehensive mechanical and mechatronic design process, encompassing modeling, optimization of electrical energy consumption, component selection, and benchtop and clinical evaluation. This thesis describes the detailed design and analysis of the CyAn prosthesis, including a parametric model for predicting device performance, fatigue life calculations, and mechanical integrity assessments of device components. Benchtop testing results confirm that the device successfully achieves the targeted performance metrics, demonstrating its capability to replicate natural gait mechanics. The clinical validation study was conducted with 3 participants with unilateral transtibial amputation at 3 different walking conditions: level ground at 1.5 m/s, uphill (+10◦ slope) at 0.8 m/s, and downhill (-10◦ slope) at 1.2 m/s. During the experiment, the subjects walked on an instrumented treadmill to regulate the walking speed while force and motion data were recorded. The results of these tests demonstrate the prosthesis design’s capability to replicate natural gait mechanics and kinetics, as well as insights into further improvements and adaptations. This thesis comprehensively details the mechanical and mechatronic design processes, encompassing modeling, optimization, component selection, and empirical evaluation of the CyAn prosthesis. This thesis presents the first of its kind rotary powered ankle-foot prosthesis, utilizing a cycloidal drive mechanism and a custom series carbon fiber spring. Compared to existing powered devices, the CyAn offers a lower device mass and increased biomimetic functionality, making it a cost-effective solution for improving mobility and quality of life for transtibial amputees. This research establishes a framework for developing customized prosthetic solutions that address the unique needs of individual users, with significant clinical results demonstrating the potential of the CyAn to improve health outcomes by normalizing biomechanics, increasing energy efficiency, and reducing adverse limb loading. |
| first_indexed | 2025-03-10T13:11:18Z |
| format | Thesis |
| id | mit-1721.1/158319 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2025-03-10T13:11:18Z |
| publishDate | 2025 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1583192025-03-05T15:27:24Z Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis Du, Lucy W. Herr, Hugh M. Massachusetts Institute of Technology. Department of Mechanical Engineering The prevalence of major lower limb loss in the United States is projected to increase significantly due to rising rates of diabetes and obesity, highlighting an urgent need for advanced prosthetic solutions [1]. Individuals with lower limb amputations often face increased energy expenditure and secondary musculoskeletal conditions as a result of using conventional prosthetic devices [2]. These challenges underscore the necessity for innovative prosthetic designs that can enhance user mobility and comfort. A promising prosthesis solution are powered ankle-foot prostheses, which have the potential to provide biologically accurate push-off power, thereby offering significant benefits such as improved walking economy, increased mobility, and reduced impact forces on the user’s residual limb. However, existing powered prostheses often lack customization and fail to adequately meet the diverse and specific needs of individual users, which can limit their effectiveness and adoption. This thesis introduces a personalized, optimized, low-profile powered ankle-foot prosthesis, known as the Cycloidal Ankle (CyAn), designed to achieve biological ranges of motion and torque during level-ground walking. The CyAn employs a cycloidal drive transmission and a series carbon fiber spring to mimic tendon-like compliance, which enhances energy storage and return while maintaining a low build height to accommodate a broader range of users. The prosthesis device is capable of 25◦ of dorsiflexion and 41◦ of plantarflexion, and is capable of outputting at least 130 Nm of torque during walking, corresponding to biological ankle torque during level ground walking at 1.5 m/s for a 50th percentile male [3]. The CyAn prosthesis uses of a cycloidal drive transmission coupled with a series carbon fiber spring. This combination replicates tendon-like compliance and allows for a reduced build height without compromising the prosthesis’s range of motion or mechanical performance. The development of the CyAn prosthesis involved a comprehensive mechanical and mechatronic design process, encompassing modeling, optimization of electrical energy consumption, component selection, and benchtop and clinical evaluation. This thesis describes the detailed design and analysis of the CyAn prosthesis, including a parametric model for predicting device performance, fatigue life calculations, and mechanical integrity assessments of device components. Benchtop testing results confirm that the device successfully achieves the targeted performance metrics, demonstrating its capability to replicate natural gait mechanics. The clinical validation study was conducted with 3 participants with unilateral transtibial amputation at 3 different walking conditions: level ground at 1.5 m/s, uphill (+10◦ slope) at 0.8 m/s, and downhill (-10◦ slope) at 1.2 m/s. During the experiment, the subjects walked on an instrumented treadmill to regulate the walking speed while force and motion data were recorded. The results of these tests demonstrate the prosthesis design’s capability to replicate natural gait mechanics and kinetics, as well as insights into further improvements and adaptations. This thesis comprehensively details the mechanical and mechatronic design processes, encompassing modeling, optimization, component selection, and empirical evaluation of the CyAn prosthesis. This thesis presents the first of its kind rotary powered ankle-foot prosthesis, utilizing a cycloidal drive mechanism and a custom series carbon fiber spring. Compared to existing powered devices, the CyAn offers a lower device mass and increased biomimetic functionality, making it a cost-effective solution for improving mobility and quality of life for transtibial amputees. This research establishes a framework for developing customized prosthetic solutions that address the unique needs of individual users, with significant clinical results demonstrating the potential of the CyAn to improve health outcomes by normalizing biomechanics, increasing energy efficiency, and reducing adverse limb loading. Ph.D. 2025-03-05T15:27:22Z 2025-03-05T15:27:22Z 2024-09 2025-03-03T16:17:54.650Z Thesis https://hdl.handle.net/1721.1/158319 Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Copyright retained by author(s) https://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Du, Lucy W. Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title | Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title_full | Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title_fullStr | Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title_full_unstemmed | Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title_short | Design and Evaluation of a Powered Series-Elastic Cycloidal Ankle (CyAn) Prosthesis |
| title_sort | design and evaluation of a powered series elastic cycloidal ankle cyan prosthesis |
| url | https://hdl.handle.net/1721.1/158319 |
| work_keys_str_mv | AT dulucyw designandevaluationofapoweredserieselasticcycloidalanklecyanprosthesis |