Design of constant-force mechanisms using origami

The origami mechanisms possess numerous unique advantages, including folding, reconfigurability, and multi-stability. The presence of multi-stability introduces a novel concept for the design of constant force mechanisms (CFM). In this study, we present a CFM with multi-segment constant-force regions by leveraging the multi-stable characteristics of the origami mechanism. The design principle behind this CFM involves combining an accordion origami structure with positive stiffness and a Kresling origami structure with multi-segment negative stiffness regions. To achieve zero stiffness, the Kresling origami structure is aligned parallel to the accordion origami. To effectively utilize both the Kresling and accordion origamis, we have established a mechanical model that describes their respective stiffness characteristics to establish design rules for the constant-force mechanism. By carefully designing the parameters of these two origami structures, we evaluate how variations in the structural parameters of Kresling influence the constant force properties of our proposed multi-segment CFM. To illustrate its inherent property of providing constant force across multiple segments, we employ finite element analysis and experiments to obtain force-displacement curves for our mechanism. The results demonstrate the feasibility of our presented design method which paves the way for constructing a simple CFM.