Ankle-Knee prosthesis with powered ankle and energy transfer for CYBERLEGs α-prototype

Abstract

Restoring natural walking for amputees has been increasingly investigated because of demographic evolution, leading to increased number of amputations, and increasing demand for independence. The energetic disadvantages of passive pros-theses are clear, and active prostheses are limited in autonomy. This paper presents the simulation, design and development of an actuated knee-ankle prosthesis based on a variable stiffness actuator with energy transfer from the knee to the ankle. This approach allows a good approximation of the joint torques and the kinematics of the human gait cycle while maintaining compliant joints and reducing energy consumption during level walking. This first prototype consists of a passive knee and an active ankle, which are energetically coupled to reduce the power consumption.

A user-specific human-machine interaction strategy for a prosthetic shank adapter

“…Recent advancements in active prosthetics indicate the potential of such devices [1]. Most available devices focus on straight walking [2], [3] or aid ascension or descension [4], [5]. However, approximately 40% of activities in daily life are turning motions [6] and the majority of common devices does not contain a degree of freedom in the transverse plane.…”

Advances in Propulsive Bionic Feet and Their Actuation Principles

“…This tendency is obviously due to the advantage of the SEA to significantly reduce peak power in ankle-foot prostheses. Although the VSA [11] might present interesting assets considering energy efficiency issues for different walking speeds, the research of the team that developed the CYBERLEGs prosthesis [82] is still in its debut phase and has therefore not yet shown its ability to adapt to different gaits. In a near future, one can expect interesting results from this device and an answer to the following question: "Does it pay to use a variable stiffness actuator in a prosthetic foot?"…”

“…However it is expected that devices that have already undergone clinical trials will slowly evolve to commercial products in the next coming years. The highest potential candidates at first sight seem to be Vanderbilt University's transfemoral prosthesis [51,53,81] and the Vrije Universiteit Brussel's AMP-Foot [12,13,87] and CYBERLEGs prototype [82].…”

“…The overall majority of propulsive bionic feet make use of the series elastic actuator (SEA and SEAPS) [10] while only one prosthesis proposes actuation with a variable stiffness actuator (CYBERLEGs [82]). This tendency is obviously due to the advantage of the SEA to significantly reduce peak power in ankle-foot prostheses.…”

“…The first prototype CYBERLEGs -prototype (Figure 17(a)) [82], designed for transfemoral amputees, consists of a variable stiffness MACCEPA-type actuator (200 W Brushless DC motor) [11,38] that is able to provide 100% of the push-off properties at the ankle combined with a passive knee joint consisting of locking and unlocking mechanisms to fix springs in place to imitate the knee joint torque-angle characteristics. This complex set of locking mechanisms was incorporated to enable energy transfers between the knee and the ankle in the late stance phase of walking.…”