A Modeling Framework for Jamming Structures

Abstract

Jamming is a structural phenomenon that provides tunable mechanical behavior. A jamming structure typically consists of a collection of elements with a low effective stiffness and damping. When a pressure gradient, such as vacuum, is applied, kinematic and frictional coupling increase, resulting in dramatically altered mechanical properties. Engineers have used jamming to build devices from tunable-stiffness grippers to tunable-damping landing gear. This study presents a rigorous framework that systematically guides the design of jamming structures for target applications. The force-deflection behavior of major types of jamming structures (i.e., grain, fiber, and layer) in fundamental loading conditions (e.g., tension, shear, bending) is compared. High performing pairs (e.g., grains in compression, layers in shear and bending) are identified. Parameters which go into designing, fabricating and actuating a jamming structure (e.g., scale, material, geometry, actuator) are described, along with their effects on functional metrics. Two key methods to expand on the design space of jamming structures are introduced: using structural design to achieve effective tunable-impedance behavior in specific loading directions, and creating hybrid jamming structures to utilize the advantages of different types of jamming. Collectively, this study elaborates and extends the jamming design space, providing a conceptual modeling framework for jamming-based structures.