Support provided by the Office of Naval Research

Robust Robotic Mechanisms and Sensors via Shape Deposition Manufacturing One of the greatest successes of biologically-inspired design has been the development of mechanically robust robots. One promising biomimetic facbrication technique is Shape Deposition Manufacturing (SDM), which alternates material deposition and machining to produce robot structures with compliant joints and embedded sensing and actuation elements. We explore the benefits of using Shape Deposition Manufacturing for constructing a simple two-fingered gripper and add to the tools available to robot designers by developing a range of sensing modalities compatible with the process. These include Hall-effect sensors for joint angle sensing, embedded strain gauges for 3 axis force measurements, optical reflectance sensors for tactile sensing, and piezoelectric polymers for contact detection. In addition to a simple construction process, the resulting parts are extremely robust, fully functional after high impact loads and other forces due to unintended contact.

Compliant Grasping for Unstructured Environments Compliance conveys several advantages for robotic grasping. In unstructured environments, sensing uncertainties are large and target object size and location may be poorly known. Finger compliance allows the gripper to conform to a wide range of objects while minimizing contact forces. Robot joint compliance or stiffness has often been considered in the context of active control, where active control uses sensors and actuators to achieve a desired force-deflection relationship. In contrast, passive compliance, implemented through springs in robot joints, offers additional benefits, particularly in impacts, where control loop delays may lead to poor control of contact forces. The reduced need for the sensing required to create active compliance can also lead to lower implementation costs.

"Soft" Grippers and Bugbots: Collaborators from Stanford and UC Berkley have designed and produced a robot modeled after the cockroach, utilizing knowledge of the insect's locomotion characteristics and new manufacturing techniques. The interesting feature of the robot is a passive rubber spring joint connecting the legs to the body. This joint, mimicking the springy, resilin lined joints of the insect, aids in disturbance rejection, accomplished without sensory feedback. Our contribution to the project will be a mechanical gripper designed using similar, passive spring joints with variable stiffness, which will aid in the task of grasping an object in a unfamiliar environment, without the use of complex sensory technology.