# Experimental Study of Vibration Isolation Characteristics of a Geometric Anti-Spring Isolator
## 5 Conclusions  
In this paper, a geometric anti-spring isolator made up of several cantilever blade springs is developed. The idea of optimization based on the genetic algorithm is utilized to mathematically solve the differential boundary problem of static mechanical of the geometric anti-spring isolation structure. The dimensionless optimal design parameters of geometric anti-spring isolation structure for different nonlinear geometric parameters are achieved. A Matlab/Simulink program is used to explore the transmissibility of the geometric anti-spring isolator under base excitation. The effects of the nonlinear geometric parameter, excitation displacement amplitude, load weight and damping on the transmissibility of the geometric anti-spring isolator are discussed. A single degree of the freedom vibration evaluation system is established to investigate the vibration isolation performance and nonlinearity characteristics of the geometric anti-spring isolator with a nonlinear geometric parameter of 0.92. Discrete sine excitation experiment and linear frequency sweep excitation experiment are carried out. The initial isolation frequency is used to describe the low-frequency vibration isolation range of the isolator. Some conclusions are as follows:  
(1) The nonlinear geometric parameter i.e., the dimensionless horizontal coordinate of blades spring's vertex is the key parameter to decide the mechanical property of the geometric anti-spring isolator. With the decrement of the nonlinear geometric parameter, the dynamic stiffness of the isolator decreases quickly. When the nonlinear geometric parameter is 0.9027, the minimum dynamic stiffness approaches zero.  
(2) The geometric anti-spring isolator under the rated load has a hardening-type stiffness characteristic. As the excitation amplitude increases, the nonlinearity of the isolator enhances.  
(3) The imperfection of load weight will largely change the resonance frequency and nonlinearity characteristic of the geometric anti-spring isolator. When the working load goes away from the rated load, the resonance frequency of the geometric anti-spring isolator increases and the nonlinearity type of the isolator varies with the increment of the excitation amplitude. When the excitation amplitude is small, the isolator shows a softening-type stiffness characteristic. When the excitation amplitude is large, the isolator shows a hardening-type stiffness characteristic.  
(4) By increasing the damping, the nonlinearity of the isolator will be weakened. The attenuation rate in the isolation area does not change if the damping is not too large.  
(5) The experiment shows that the designed isolator has good low-frequency isolation performance. Under the rated working load, the initial isolation frequency is not larger than 3.6 Hz. With the excitation amplitude increases, the initial isolation frequency of the isolator decreases linearly. When the working load is changed, the initial isolation frequency will be enlarged. In the frequency sweep excitation experiment, both upward jumping and downward jumping phenomena are observed, which demonstrates that the geometric anti-spring isolator had complex nonlinearity characteristics when damping is light. The nonlinearity characteristics of the geometric anti-spring isolator vary as the excitation amplitude increases.  
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Financial support from the Chinese Academy of Sciences (Grant No. XDB22040502) was gratefully acknowledged. This study was also supported by the Collaborative Innovation Center of Suzhou Nano Science and Technology.  
The idea was proposed by [PERSON] and he gave suggestions about the experimental design. [PERSON] completed the experiment and mathematically simulation and wrote the manuscript. Both authors discussed the results and revised the manuscript.  
The authors declare no conflict of interest.