Abstract
This research presents the design and preliminary evaluation of an electromyographically (EMG) controlled 2-degree-of-freedom (DOF) ankle-foot prosthesis designed to enhance rock climbing ability in persons with transtibial amputation. The prosthesis comprises motorized ankle and subtalar joints, and is capable of emulating some key biomechanical behaviors exhibited by the ankle-foot complex during rock climbing maneuvers. The free space motion of the device is volitionally controlled via input from EMG surface electrodes embedded in a custom silicone liner worn on the residual limb. The device range of motion is 0.29 radians of each dorsiflexion and plantar flexion, and 0.39 radians each of inversion and eversion. Preliminary evaluation of the device was conducted, validating the system mass of 1292 grams, build height of 250 mm, joint velocity of 2.18 radians/second, settling time of 120 milliseconds, and steady state error of 0.008 radians. Clinical evaluation of the device was performed during a preliminary study with one subject with transtibial amputation. Joint angles of the ankle-foot, knee, and hip were measured during rock climbing with the robotic prosthesis and with a traditional passive prosthesis. We found that the robotic prosthesis increases the range of achieved ankle and subtalar positions compared to a standard passive prosthesis. In addition, maximum knee flexion and hip flexion angles are decreased while climbing with the robotic prosthesis. These results suggest that a lightweight, actuated, 2-DOF EMG-controlled robotic ankle-foot prosthesis can improve ankle and subtalar range of motion and climbing biomechanical function.
Highlights
C URRENT lower extremity prosthesis research and development largely focus on the design and control of devices to increase mobility and improve function during activitiesManuscript received November 19, 2019; revised May 16, 2020 and August 6, 2020; accepted October 18, 2020
The maximum plantar flexion achieved with the robotic prosthesis is −0.25 radians, and maximum dorsiflexion is 0.07 radians
Maximum knee flexion is lower while climbing with the powered prosthesis, −0.69 radians compared to −1.06 radians with the passive prosthesis
Summary
C URRENT lower extremity prosthesis research and development largely focus on the design and control of devices to increase mobility and improve function during activities. Manuscript received November 19, 2019; revised May 16, 2020 and August 6, 2020; accepted October 18, 2020. Date of publication October 23, 2020; date of current version February 25, 2021. Clites was with the Center for Extreme Bionics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA. He is with the Anatomics Laboratory, University of California at Los Angeles (UCLA), Los Angeles, CA 90095 USA
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