# Design Methodology and Application Dynamics of Compact Quasi-Zero Stiffness Isolators
## 3 Compact Design of QZS Isolation
### Origami-Inspired Type  
Origami-inspired structural design represents a geometrically driven methodology founded upon principles derived from traditional paper folding art. This approach employs systematic folding methodologies to generate sophisticated geometric configurations and spatial architectures. Such origami-derived structures exhibit inherent mechanical characteristics of significant scientific interest, including bistable behavior, pronounced nonlinear  
Figure 13: Metamaterial cell: (**a**) Lattice core sandwich beam design proposed by [PERSON] et al. [75]; (**b**) Miur tube and QZS structure proposed by [PERSON] et al. [76]; (**c**) Multi-stage QZS metamaterial cell design proposed by [PERSON] et al. [77].  
responses, and adjustable stiffness properties. These distinctive attributes establish novel application prospects for developing QZS isolators. As demonstrated in Figure 14, exemplary configurations of origami-based isolators showcase the practical implementation of these structural principles.  
[PERSON] et al. [84] introduced a truss spring-based design to replace the deformable creases in the traditional origami structure to improve the realizability in engineering applications and also to achieve the bistable and QZS properties by adjusting the system parameters and selecting different springs. Based on the above model, [PERSON] et al. [85] investigated the effects of self-weight and damping nonlinearity of the origami structure on the dynamic performance of origami vibration isolators and concluded that the faceted mass of the origami structure and the lighter bottom faceted plate would provide better isolation performance. [PERSON] et al. [86] proposed an origami-based vibration isolation system integrated with elastic joints, and vibration experiments showed that the effective isolation frequency of this vibration isolator was below 2 Hz. [PERSON] et al. [87] proposed a lightweight vibration isolator based on the Kresling origami module with expandable and QZS characteristics, which can achieve the full frequency range of vibration isolation with small excitation amplitude and high damping and can increase the suppression effect of large-value vibration by series connection arrangement. Inspired by the symmetric conical Kresling origami unit and an axial spring, [PERSON] et al. [88] proposed a vibration isolation system consisting of two symmetric conical Kresling origami units and an axial spring, which has a lower starting vibration isolation frequency compared with the existing QZS damper system. [PERSON] et al. [89] proposed a new combined truss spring structure based on a triangular cylindrical origami model with an additional inertia mechanism, which uses elastic connecting rods to simulate all the folds to realize the adjustable stiffness and inertia.  
Figure 14: Origami structure: (**a**) Truss spring instead of deformable crease [84]; (**b**) Schematic of origami structure with self-weighting blocks [85]; (**c**) Two symmetrical conical Kresling origami units and an axial spring form the vibration isolation system [88]; (**d**) Truss-spring structure with additional inertia mechanism combination [89].  
The foldability, lightweight, and specific mechanical properties of origami structures make them ideal for QZS isolation design. However, there are many challenges in the practical application, the most critical one being how to smoothly transition from abstract theoretical modeling to practical engineering applications.