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Bio-inspired design and validation of the Efficient Lockable Spring Ankle (ELSA) prosthesis

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Original languageEnglish
Title of host publication2019 IEEE 16th International Conference on Rehabilitation Robotics (ICORR)
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages6
ISBN (Electronic)978-1-7281-2755-2
ISBN (Print)978-1-7281-2756-9
Publication statusPublished - 29 Jul 2019
Event16th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics (ICORR 2019) - Metro Toronto Convention Centre, Toronto, Canada
Duration: 24 Jun 201928 Jun 2019

Publication series

PublisherInstitute of Electrical and Electronics Engineers
ISSN (Print)1945-7898
ISSN (Electronic)1945-7901


Conference16th IEEE/RAS-EMBS International Conference on Rehabilitation Robotics (ICORR 2019)
Abbreviated titleICORR 2019
Internet address


Over the last decade, active lower-limb prostheses demonstrated their ability to restore a physiological gait for transfemoral amputees by supplying the required positive energy balance during daily life locomotion activities. However, the added-value of such devices is significantly impacted by their limited energetic autonomy, excessive weight and cost preventing their full appropriation by the users. There is thus a strong incentive to produce active yet affordable, lightweight and energy efficient devices. To address these issues, we developed the ELSA (Efficient Lockable Spring Ankle) prosthesis embedding both a lockable parallel spring and a series elastic actuator, tailored to the walking dynamics of a sound ankle. The first contribution of this paper concerns the development of a bio-inspired, lightweight and stiffness adjustable parallel spring, comprising an energy efficient ratchet and pawl mechanism with servo actuation. The second contribution is the addition of a complementary rope-driven series elastic actuator to generate the active push-off. The system produces a sound ankle torque pattern during flat ground walking. Up to 50% of the peak torque is generated passively at a negligible energetic cost (0:1 J=stride). By design, the total system is lightweight (1:2 kg) and low cost.


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