Two-Sheet Type Rotary-Driven Thin Bending Mechanism Realizing High Stiffness

Thin construction is an advantage in the design of mechanisms. Among them, the soft-bending thin sheet actuator can fit into the shape of an object and grasp it after inserting a finger into a narrow space. However, to facilitate bending, these mechanisms are thin or made of soft materials, which leads to low stiffness. In this study, we proposed a thin metal sheet actuator that deforms its cross-section in accordance with the bending motion to achieve both thinness and rigidity. It was composed of two metal sheets connected with rotational joints and links. We focused on the anisotropic bending stiffness of the metal sheet and realized a three-dimensional deformation structure; it can be driven only with rotary-driven input using both torsional and bending deformations of the sheet. The experimental results indicate that the stiffness is up to 8.7 times higher compared to the undeformed sheet structure. In addition, we used this mechanism to realize a thin finger mechanism with a lifting motion after inserting a narrow gap between the object and the floor. Additionally, we realized a compliant contacting motion by focusing on different elasticities depending on the direction of bending.