Design and experimental validation of a vibration isolator with high-static low-dynamic stiffness and operating point variable property

2021 ◽  
pp. 107754632199052
Author(s):  
Zhenhua Zhou ◽  
Minrui Zhou ◽  
Zhihui Dai ◽  
Xin Liu ◽  
Zhanhui Li
Keyword(s):  
Experimental Validation ◽  
Dynamic Stiffness ◽  
Negative Stiffness ◽  
Vibration Isolator ◽  
Coil Spring ◽  
Variable Property ◽  
Leaf Springs ◽  
Stiffness Characteristic ◽  
Vibration Transmissibility ◽  
And Performance

Vibration isolator with high-static low-dynamic stiffness property has been researched extensively, but the isolator’s stability and performance will be deteriorated with the operation point variation. In this article, a vibration isolator that operation point can be variable was proposed, and it was constructed by combining a coil spring and flexible leaf springs with a negative stiffness magnet spring in parallel. Unlike previous studies, this article focuses on the realization of the high-static low-dynamic stiffness characteristic of the isolator, and the operation point of the vibration isolator can be varied in a certain range. The effects of configuration parameters on the negative stiffness are investigated in detail. Furthermore, the designing procedure to realize the linear negative stiffness with the expected magnitude and range was also developed. A prototype was installed and the vibration transmissibility of the system at different operation points was measured, the experimental results indicated that the isolator can be kept stable in different operation points, and the performance does not deteriorate with the variation of the operation point. The effectiveness of the designing procedure of the realization of linear negative stiffness with the expected magnitude and range and the variable of the operation point of the isolator was validated.

The design of negative stiffness spring for precision vibration isolation using axially magnetized permanent magnet rings

2019 ◽  
Vol 25 (19-20) ◽  
pp. 2667-2677 ◽  
Author(s):  
Zhenhua Zhou ◽  
Shuhan Chen ◽  
Dun Xia ◽  
Jianjun He ◽  
Peng Zhang
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Design Procedure ◽  
Air Gap ◽  
Negative Stiffness ◽  
Linear Component ◽  
Vibration Isolator ◽  
Stiffness Characteristic ◽  
Isolation Performance

A negative stiffness element is always employed to generate high-static–low-dynamic stiffness characteristic of the vibration isolator, reduce the resonance frequency of the isolator, and improve the vibration isolation performance under low and ultra-low frequency excitation. In this paper, a new compact negative stiffness permanent magnetic spring (NSPMS) that is composed of two axial-magnetized permanent magnetic rings is proposed. An analytical expression of magnetic negative stiffness of the NSPMS is deduced by using the Coulombian model. After analyzing the effect of air-gap width, air-gap position, height difference between the inner ring and outer ring on the negative stiffness characteristic, a design procedure is proposed to realize the negative stiffness characteristic with a global minimum linear component and uniformity stiffness near the equilibrium position. Finally, an experimental prototype is developed to validate the effectiveness of the NSPMS. The experimental results show that combining a vibration isolator with the NSPMS in parallel can lower the natural frequency and improve the isolation performance of the isolator.

Design of a Miniaturized Pneumatic Vibration Isolator With High-Static-Low-Dynamic Stiffness

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Yuhu Shan ◽  
Wenjiang Wu ◽  
Xuedong Chen
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Structure Design ◽  
Negative Stiffness ◽  
Vibration Isolator ◽  
Load Bearing Capacity ◽  
Compact Structure ◽  
Chamber Volume ◽  
Isolation Systems ◽  
Magnetic Rings

In the ultraprecision vibration isolation systems, it is desirable for the isolator to have a larger load bearing capacity and a broader isolation bandwidth simultaneously. Generally, pneumatic spring can bear large load and achieve relatively low natural frequency by enlarging its chamber volume. However, the oversized isolator is inconvenient to use and might cause instability. To reduce the size, a miniaturized pneumatic vibration isolator (MPVI) with high-static-low-dynamic stiffness (HSLDS) is developed in this paper. The volume of proposed isolator is minimized by a compact structure design that combines two magnetic rings in parallel with the pneumatic spring. The two magnetic rings are arranged in the repulsive configuration and can be mounted into the chamber to provide the negative stiffness. Then dynamic model of the developed MPVI is built and the isolation performances are analyzed. Finally, experiments on the isolator with and without the magnetic rings are conducted. The final experimental results are consistent with the dynamical model and verify the effectiveness of the developed vibration isolator.

scholarly journals A bistable mechanism with linear negative stiffness and large in-plane lateral stiffness: design, modeling and case studies

2020 ◽  
Vol 11 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Zhanfeng Zhou ◽  
Yongzhuo Gao ◽  
Lining Sun ◽  
Wei Dong ◽  
Zhijiang Du
Keyword(s):  
Vibration Isolation ◽  
Compliant Mechanism ◽  
Dynamic Stiffness ◽  
Negative Stiffness ◽  
Analytical Models ◽  
Lateral Stiffness ◽  
Constant Force ◽  
The Novel ◽  
Stiffness Characteristic ◽  
Bistable Mechanism

Abstract. To overcome the limitations of conventional bistable mechanisms, this paper proposes a novel type of bistable mechanism with linear negative stiffness and large in-plane lateral stiffness. By connecting the novel negative-stiffness mechanism in parallel with a positive-stiffness mechanism, a novel quasi-zero stiffness compliant mechanism is developed, which has good axial guidance capability and in-plane lateral anti-interference capability. Analytical models based on a comprehensive elliptic integral solution of bistable mechanism are established and then the stiffness curves of both conventional and novel bistable mechanisms are analyzed. The quasi-zero stiffness characteristic and High-Static-Low-Dynamic-Stiffness characteristic of the novel compliant mechanism are investigated and its application in constant-force mechanism and vibration isolator is discussed. A prototype with adjustable load-carrying capacity is designed and fabricated for experimental study. In the two experiments, the effectiveness of the proposed quasi-zero stiffness mechanism used in the field of constant-force output and vibration isolation is tested.

scholarly journals An Air Spring Vibration Isolator Based on a Negative-Stiffness Structure for Vehicle Seat

2021 ◽  
Vol 11 (23) ◽  
pp. 11539
Author(s):  
Cong Hung Nguyen ◽  
Cong Minh Ho ◽  
Kyoung Kwan Ahn
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Negative Stiffness ◽  
Vibration Isolator ◽  
Air Spring ◽  
Nonlinear Force ◽  
Mechanical Spring ◽  
Negative Stiffness Mechanism ◽  
Vehicle Seat

This research introduces an air spring vibration isolator system (ASVIS) based on a negative-stiffness structure (NSS) to improve the vehicle seat’s vibration isolation performance at low excitation frequencies. The main feature of the ASVIS consists of two symmetric bellows-type air springs which were designed on the basis of a negative stiffness mechanism. In addition, a crisscross structure with two straight bars was also used as the supporting legs to provide the nonlinear characteristics with NSS. Moreover, instead of using a vertical mechanical spring, a sleeve-type air spring was employed to provide positive stiffness. As a result, as the weight of the driver varies, the dynamic stiffness of the ASVIS can be easily adjusted and controlled. Next, the effects of the dimension parameters on the nonlinear force and nonlinear stiffness of ASVIS were analyzed. A design process for the ASVIS is provided based on the analytical results in order to achieve high static–low dynamic stiffness. Finally, numerical simulations were performed to evaluate the effectiveness of the ASVIS. The results obtained in this paper show that the values of the seat displacement of the ASVIS with NSS were reduced by 77.16% in comparison with those obtained with the traditional air spring isolator without NSS, which indicates that the design of the ASVIS isolator with NSS allows the effective isolation of vibrations in the low-frequency region.

Modelling and Performance of an Experimental Active Vibration Isolator

1995 ◽  
Vol 117 (3A) ◽  
pp. 272-278 ◽  
Author(s):  
L. R. Miller ◽  
M. Ahmadian ◽  
C. M. Nobles ◽  
D. A. Swanson
Keyword(s):  
Transfer Functions ◽  
Dynamic Stiffness ◽  
Graph Model ◽  
Electromagnetic Actuator ◽  
Vibration Isolator ◽  
Bond Graphs ◽  
Inertia Effects ◽  
Active Vibration ◽  
And Performance ◽  
Insight Into

The performance of an active vibration isolator consisting of a fluid mount and an electromagnetic actuator is discussed. The electromagnetic actuator augments the inertia effects of the fluid mount to reduce the dynamic stiffness of the mount at the vibrational disturbance frequencies of the engine. The active isolator is modeled using bond graphs. Dynamic stiffness, blocked force, and free displacement transfer functions are developed from the bond graph model to gain insight into the active mount’s performance. A mount effectiveness analysis shows that reducing the mount’s dynamic stiffness results in better dynamic isolation. Numerical simulations along with laboratory testing of the active isolator are used to evaluate the performance of the mount. A simple laboratory experiment shows that an active mount can be controlled to have a dynamic stiffness that is 100 times (40 dB) lower than a passive mount, without sacrificing static stiffness.

scholarly journals An Ultra-Low Frequency Two DOFs’ Vibration Isolator Using Positive and Negative Stiffness in Parallel

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Min Wang ◽  
Xuedong Chen ◽  
Xiaoqing Li
Keyword(s):  
Natural Frequency ◽  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Vertical Direction ◽  
Negative Stiffness ◽  
Effective Bandwidth ◽  
Vibration Isolator ◽  
Analysis System ◽  
The Stability

With the improvement of performance in the ultra-precision manufacturing engineering, the requirements for vibration isolation have become increasingly stringent. In order to get wider effective bandwidth and higher performance of vibration isolation in multiple DOFs system, an ultra-low frequency two DOFs’ vibration isolator with positive and negative stiffness in parallel (PNSP) is proposed. The two DOFs’ isolator which combines a positive stiffness (PS) air spring with a negative stiffness (NS) magnetic spring in parallel and combines a PS flat spring with an NS inverted pendulum in parallel is designed to reduce the natural frequency and broaden the effective bandwidth in horizontal and vertical direction. Based on this structure, stiffness models of different components in different directions are established. Compared with a PS isolator, it possesses the characteristic of high-static-low-dynamic stiffness. The simulation curves also provide strong evidence. Last, a real-time active control system and a spectrum testing and analysis system are used for the contrast experiment between the mentioned PNSP structure and PS only. The experimental results demonstrate that the isolator with PNSP can obviously reduce the natural frequency to 1 Hz and simultaneously maintain the stability of the system and consequently verify the validity and superiority of the mentioned structure.

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