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Compliant Structures |
Instead of distributing stiff material throughout a structure, this work is focused on methods of distributing compliance selectively within a structure to enable it to move. Jacob Diez finished his Master’s Thesis research under the advisement of Imme Ebert-Uphoff on their project “Design for Additive Fabrication: Building Miniature Robotic Mechanisms.” This project addresses the potential to build robotic systems (composed of rigid links, joints, actuators, and sensors) utilizing the strengths of Additive Fabrication. Miniature robotic systems are well suited for manufacture with additive fabrication techniques because these techniques have the capabilities to build both fine geometries (used for joint designs) and internal geometries (used to hold actuators and sensors). Jacob demonstrated a series of impressive devices. First, he developed different types of compliant joints. These joints demonstrate compliance only along the intended axis of rotation, and have achieved rotations up to +/- 200?. Shape Memory Alloy (SMA) actuators were utilized to successfully create motion in the robotic systems as well. These achievements led to the creation of a miniature robotic device as well as a model of the human hand (see images below). The miniature robot has 2 DOF and the hand has 9 DOF, 9 SMA actuators, 13 compliant joints, and the fingers can achieve approximately 50? of cumulative motion. Both of these devices show the clear potential for a non-assembly robotic mechanism that is able to achieve motion. In addition to compliant joints and actuators, it is also important to integrate sensors into these devices. After a review of suitable sensing technologies, a simple type of sensor, called a strip sensor, was selected for further study. Basically, strip sensors change resistance (electrical) as a result of bending them. By placing these sensors across a compliant joint, the deflection of the joint can be directly measured. Jacob demonstrated the use of 6 strip sensors in a hexagon-shaped ring of 6 compliant joints. By deforming this ring, the sensors communicate with a host computer to sense the deformation and display a model of the deformed ring on the computer screen. These demonstrations helped lead to the key ideas behind the Digital Clay project, described next. |
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