Date of download: 10/25/2017 Copyright © ASME. All rights reserved. From: An Active Foot-Ankle Prosthesis With Biomechanical Energy Regeneration J. Med. Devices. 2010;4(1):011003-011003-9. doi:10.1115/1.4001139 Figure Legend: 3D plot of the RE40 motor efficiency as a function of motor torque (Nm) and motor angular velocity (rpm) . Notice that the highest efficiency of 91% is only achieved at a narrow range of torque and angular velocity. Operating the RE40 at speeds lower than 2000 rpm or torque above 0.2 Nm will significantly degrade the motor efficiency. Illustrated in the figure are two points on the mesh.