@article{c83fd770bf994659b834ea75b705b4ad,
title = "A two-axis cable-driven ankle-foot mechanism",
abstract = "This paper describes a novel cable-driven ankle-foot mechanism with two controllable degrees of freedom (DOF) in dorsiflexion-plantarflexion (DP) and inversion-eversion (IE). The presented mechanism is a proof of concept to demonstrate feasibility. Ankle kinematic measurements demonstrate that ankle IE rotations during a step turn are significantly different from walking on a straight path. This suggests that the ankle-foot mechanisms used in prostheses, exoskeletons, and bipedal robots can be improved by controlling a second degree of freedom in the frontal plane. The proposed prototype mechanism is described in detail, and its design considerations and parameters are presented. The mechanism is capable of producing trajectories similar to the human ankle during a step turn. The device shows passive mechanical impedance close to the human ankle mechanical impedance, allowing its mechanical impedance to be controlled using an impedance controller. The presented mechanism is capable of providing key mechanical characteristics similar to the human ankle, including power, range of motion, and weight, suggesting the feasibility of this design concept.",
keywords = "Ankle impedance, Ankle mechanism, Ankle rotations, Cable-driven prosthesis, Human ankle kinematics, Multi-axis ankle-foot prosthesis, Powered lower extremity prosthesis, Turning, Two-DOF ankle-foot",
author = "Ficanha, {Evandro M.} and Mohammad Rastgaar and Kaufman, {Kenton R.}",
note = "Funding Information: The prototype design consists of two DC motors and planetary gear heads (A) powered by two motor controllers (B) connected to two quadrature encoders (C) (Figure 1). Two cable drums (D) transfer the required torque to the ankle through the shock-absorbing nylon rope (E). The rope is securely attached to the cable drums to avoid slippage. A universal joint (F) connects the pylon to the foot and is supported by an elastomer to provide passive stiffness and damping to the ankle. The cable is directed to the foot with pulleys (G). The cable is attached to a carbon fiber plate (H), which is connected to a commercially available prosthetic foot (Otto Bock Axtion{\textregistered}) (I). In the rear side of the carbon fiber plate, the cable is mounted to both sides of the longitudinal axis of the foot. At the front side of the carbon fiber plate, the cable passes through a pulley (J). Torque feedback, which will be explored later, is provided by six strain gauges in the foot (K) using two strain gauge amplifiers (L). An analog to digital converter (M) is connected to a remote computer and is used to acquire the sensors data and provide the motor controllers{\textquoteright} inputs. Funding Information: This material is based upon work supported by the National Science Foundation under CAREER Grant No. 1350154.",
year = "2014",
month = nov,
day = "2",
doi = "10.1186/s40638-014-0017-0",
language = "English (US)",
volume = "1",
journal = "Mathematische Zeitschrift",
issn = "0025-5874",
publisher = "Springer New York",
number = "1",
}