A composite manipulator utilizing rotary piezoelectric motors: new robotic technologies for Mars

We report a significant advance in space robotics design based on innovation of 3D composite structures and piezoelectric actuation. The essence of this work is development of a new all-composite robotic manipulator utilizing rotary ultrasonic motors (USM). “MarsArmII“ is 40% lighter than a prior “MarsArmI” JPL design based in more massive, bulky hybrid metal-composite, joint-link system architecture and DC-motor driven actuation. MarsArmII is a four d.0.f. torso-shoulder-elbow, wrist-pitch robot of over two meters length, weighing four kilograms, and carrying a one kilogram multi-functional science effector with actuated opposable scoops, micro-viewing camera, and active tooling (abrader). MarsArmIP construction is composite throughout, with all critical load-bearing joints and effector components being based in a new 3D air layup carbon fiber RTM composite process of our design, and links formed of 2D graphite epoxy. The 3D RTM composite is machinable by traditional metal shop practice, and in early tests such parts bench-marked favorably with aluminum based designs. Each arm link incorporates a surface mounted semiconductor strain gauge, enabling force-referenced closed loop positioning. The principal arm joints are six in-lb rotary USMs acting under optically encoded PID servo control through harmonic drives. We have demonstrated the M a r s M system for inverse kinematics positioning tasks (utilizing computer vision derived stereo workspace coordinates) that include simulated Martian soil trenching, sample acquisition and instrument transfers, and fresh rock surface exposure by abrasion..