A robotic arm that consists of three joints with four degrees of freedom (DOF) has been developed. It can carry an end-effector to acquire and transfer samples by using active control and comply with surface topology in a passive mode during a brief surface contact. The three joints are arranged in such a way that one joint of two DOFs is located at the shoulder, one joint of one DOF is located at the elbow, and one joint of one DOF is located at the wrist. Operationally, three DOFs are moved in the same plane, and the remaining one on the shoulder is moved perpendicular to the other three for better compliance with ground surface and more flexibility of sample handling. Three out of four joints are backdriveable, making the mechanism less complex and more cost effective.

Having joints of a robotic arm accomplish two different tasks is a new concept. The preliminary engineering shows this concept is workable with proper selection of actuators.

This work was done by Jun Liu, Michael L. Underhill, Brian P. Trease, and Randel A. Lindemann of Caltech for NASA’s Jet Propulsion Laboratory. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it.. NPO-47099

Motion Control Technology Magazine

This article first appeared in the August, 2010 issue of Motion Control Technology Magazine.

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