An Efficient Robotic Tendon for Gait Assistance

Abstract

A robotic tendon is a spring based, linear actuator in which the stiffness of the spring is crucial for its successful use in a lightweight, energy efficient, powered ankle orthosis. Like its human analog, the robotic tendon uses its inherent elastic nature to reduce both peak power and energy requirements for its motor. In the ideal example, peak power required of the motor for ankle gait is reduced from 250 W to just 77 W. In addition, ideal energy requirements are reduced from nearly 36 J to just 21 J. Using this approach, an initial prototype has provided 100% of the power and energy necessary for ankle gait in a compact 0.95 kg package, seven times less than an equivalent motor/gearbox system.

Design of a novel knee joint for an exoskeleton with good energy efficiency for load-carrying augmentation

“…Hollander et al claimed that using a spring in series with an actuator for the ankle can reduce the peak motor power from 250 W to only 77 W [3]. Collins and Kuo developed an energy-recycling artificial foot that reduced the actuator's required power by capturing the collision energy and returning it for the push-off action [4].…”

Ankle–knee prosthesis with active ankle and energy transfer: Development of the CYBERLEGs Alpha-Prosthesis

“…In addition to the newest commercial models, there are a number of active ankle [10][11][12][13] and knee modules [14], as well as combined ankle-knee systems [15] under development, seeking to improve functionality and reduce energy consumption of both the device and the individual. These new devices have been spurred by developments in materials, electric motors, batteries, and miniaturized controllers, combined with actuators that are better suited to biomechanical use [16][17][18]. All of the modern ankle prostheses utilize some sort of passive compliance in their ankle designs.…”

A Robust Control Concept for Robotic Ankle Gait Assistance

“…One such actuator is the the Robotic Tendon [2]. The Robotic Tendon features a 'tuned' spring that is positioned at the end of a linear actuator.…”