Varying the stiffness of Lamina Emergent Joint through origami and mortise-tenon structure

Abstract

The variable stiffness joints can balance accuracy and safety compared to the single stiffness joints. To further explore the variable stiffness mode of Lamina Emergent Joint (LEJ), we designed a passive variable stiffness LEJ (PVS-LEJ) based on origami and mortise-tenon structure. Compared to the active variable stiffness flexible joints, the stiffness of PVS-LEJ can be adjusted according to load. This paper describes the working principle and design process of the PVS-LEJ in detail and explains the calculation process of block sizes. Then some simulation tests are conducted on the PVS-LEJ. The simulation results show that the contact between two blocks gradually failed in the high stiffness mode of the PVS-LEJ, and the stiffness deviated significantly from the theoretical calculation value. To address this contact failure problem, the PVS-LEJ is improved. The improved PVS-LEJ is also simulated, and the results indicate that the position where stiffness varies is the same as the design. The stiffness obtained from the simulation and theoretical calculation is consistent with each other, with an error of about 2%. Besides, some experimental tests are performed to verify the feasibility of PVS-LEJ. Finally, some problems encountered during the fabrication of PVS-LEJ are discussed, and appropriate suggestions are given.