Here you can find CAD files, assembly instructions, assembly videos, specs, etc. for fabricating linear Series Elastic Actuator SEA23-23. Feel free to use the files, but note that neither IHMC nor Yobotics, Inc. provides any warranty, guarantee, or liability of anysort whatsoever. The files are AS-IS and will require someone skilled in the art of mechatronics and robotics to derive any value from them.
These actuators used to be available for sale by Yobotics, Inc., but are no longer. Instead the design has been made open source on these pages. If you do use these designs, please let us know and send us a link that we can add here. If you improve on the designs (which we recommend), please let us know so we can improve on ours.
Fabrication and construction is relatively straightforward for someone versed in custom robot design and construction. The most complex parts are: acquiring the custom ball screw, removing the magnets from the shaft of the motor if you don't get a motor part set, compressing the springs during assembly, various glueing operations during assembly, being careful not to bend the ball screw during assembly.
Series Elastic Actuators provide many benefits in force control of robots in unconstrained environments. These benefits include high force fidelity, extremely low impedance, low friction, and good force control bandwidth. Series Elastic Actuators employ a novel mechanical design architecture which goes against the common machine design principal of “stiffer is better”. A compliant element is placed between the gear train and driven load to intentionally reduce the stiffness of the actuator. A position sensor measures the deflection, and the force output is accurately calculated using Hooke’s Law (F=Kx). A control loop then servos the actuator to the desired output force. The resulting actuator has inherent shock tolerance, high force fidelity and extremely low impedance. These characteristics are desirable in many applications including legged robots, exoskeletons for human performance amplification, robotic arms, haptic interfaces, and adaptive suspensions.
Publications related to SEAs can be found here.