The design and technical evaluation of ERiKA
An Energy Recovering Knee-Ankle prosthesis that provides support during standing up and sitting down
S.G. van der Helm (TU Delft - Mechanical Engineering)
Heike Vallery – Mentor (TU Delft - Biomechatronics & Human-Machine Control)
G Smit – Graduation committee member (TU Delft - Medical Instruments & Bio-Inspired Technology)
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Abstract
The Sit-to-Stand (SitTS) and Stand-to-Sit (StandTS) transitions are among the most demanding activities of daily living in terms of required muscle strength. Many elderly struggle with the transitions, which become even harder after a transfemoral amputation. The current state of the art in knee prostheses does not supply any support to reduce the required muscle strength. A new, energy-recovering ankle-knee prosthesis was designed to provide support during SitTS and StandTS, with a natural torque profile. The prosthesis uses pneumatic cylinders to store energy during StandTS, and recover it during SitTS. To make the use of the prosthesis as intuitive as possible, the design was optimized to mimic natural torque profiles during the transition. The addition of an ankle joint enables a more posterior placement of the prosthetic limb, which should reduce the required knee torque. The prototype provides a peak extending knee torque of 21.7 Nm and a peak plantarflexing ankle torque of 10.8 Nm during SitTS, which can be further increased by increasing the pre-pressure in the system. It is concluded that the current prototype has the potential to provide support during the SitTS and StandTS transitions, but that alterations are required to improve the available joint torques. The next phase will be user tests with transfemoral amputees.