Performance of optimised prosthetic ankle designs that are based on a hydraulic variable displacement actuator (VDA)

Gardiner, James; Bari, AZ; Kenney, Laurence; Twiste, Martin; Moser, David; Zahedi, Saeed; Howard, David

Abstract

Current energy storage and return (ESR) prosthetic
feet only marginally reduce the cost of amputee locomotion
compared to basic solid ankle cushioned heel (SACH) feet,
possibly due to their lack of push-off at the end of stance. To our knowledge, a prosthetic ankle that utilises a hydraulic variable displacement actuator (VDA) to improve push-off performance has not previously been proposed. Therefore, here we report a design optimisation and simulation feasibility study for a VDA based prosthetic ankle. The proposed device stores the eccentric ankle work done from heel strike to maximum dorsiflexion in a
hydraulic accumulator and then returns the stored energy to
power push-off. Optimisation was used to establish the best
spring characteristic and gear ratio between ankle and VDA. The corresponding simulations show that, in level walking, normal push-off is achieved and, per gait cycle, the energy stored in the accumulator increases by 22% of the requirements for normal push-off. Although the results are promising, there are many unanswered questions and, for this approach to be a success, a new miniature, low-losses, lightweight VDA would be required that is half the size of the smallest commercially available device.

Citation

Gardiner, J., Bari, A., Kenney, L., Twiste, M., Moser, D., Zahedi, S., & Howard, D. (2017). Performance of optimised prosthetic ankle designs that are based on a hydraulic variable displacement actuator (VDA). IEEE Transactions on Neural Systems and Rehabilitation Engineering, 25(12), 2418-2426. https://doi.org/10.1109/TNSRE.2017.2763999

• Journal Article Type: Article
• Acceptance Date: Oct 3, 2017
• Online Publication Date: Nov 2, 2017
• Publication Date: Dec 1, 2017
• Deposit Date: Nov 7, 2017
• Publicly Available Date: Nov 7, 2017
• Journal: IEEE Transactions on Neural Systems and Rehabilitation Engineering
• Print ISSN: 1534-4320
• Electronic ISSN: 1558-0210
• Publisher: Institute of Electrical and Electronics Engineers
• Volume: 25
• Issue: 12
• Pages: 2418-2426
• DOI: https://doi.org/10.1109/TNSRE.2017.2763999
• Publisher URL: http://dx.doi.org/10.1109/TNSRE.2017.2763999
• Related Public URLs: http://ieeexplore.ieee.org/Xplore/home.jsp; http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=7333