Design and Analysis of a Programmable Rotational Element Utilizing Coupled Kresling Origami Modules

Origami–inspired designs are being explored extensively for structural and material applications in a variety of different engineering fields because of their attractive kinematic and mechanical properties, design flexibility, and multi-functionality. However, most if not all of these studies have focused on translational motions. Utilizing origami in replacing or enhancing torsional components, such as joints, shafts and motors, has received little attention. With this in mind, this research introduces an origami-inspired rotational element via a coupled Kresling modular design (CKMD). Two Kresling origami modules with opposite chirality are integrated, achieving pure rotational motion between two ends of polygon surfaces. A model with nondimensionalized parameters is developed and a key design variable (natural height ratio) is varied to investigate the kinematic and mechanical properties of CKMD. Results show that these properties can be tailored by strategic selection of the natural height ratio, which alters the energy landscapes of both Kresling modules and leads to qualitatively distinct mechanical responses. Further investigation shows that the rotational stability characteristics of CKMD — monostability, symmetric and asymmetric bistability — may be programmed in a similar manner. Design guidelines are discussed, and the outcomes lay the foundation for integrating programmable, origami-inspired, rotational components in mechanical systems.

The Accurate Modeling and Performance Analysis of Cross-Spring Pivot as a Flexure Module

The load-displacement behavior of a cross-spring pivot as a kind of rotational element or module in compliant mechanisms is a subject of keen interest for many researchers. The model allowing not only quick design but also characteristics capture is pursued. This paper addresses some accurate closed-form results via approximations. These expressions are simple for a designer to understand the parameters without resorting to a tedious iterative procedure. The rotational displacement and center shift of the pivot are analyzed both qualitatively and quantitatively, with a general-purposed load applied including bending moment, horizontal and vertical forces. Meanwhile, a concise expression for center shift without approximations is proposed. The validity of the model is verified by finite element analysis (FEA). The relative error of the rotational displacement is less than 1.8% even if the rotational angle reaches ±20° the relative errors for the two components of center shift are less than 6% and 4% respectively, in the case of typical but general configurations and loads.