Design and experiments of a quasi–zero-stiffness isolator with a noncircular cam-based negative-stiffness mechanism

Abstract

This article presents a quasi–zero-stiffness isolator with a cam-based negative-stiffness mechanism, where the cam has a user-defined noncircular profile to generate negative stiffness to counterbalance the positive stiffness of the vertical spring and yield the quasi–zero-stiffness characteristic around the equilibrium position. Unlike previous studies, the proposed quasi–zero-stiffness isolator has the preferable feature that the desired cubic restoring force can be directly obtained through the well-designed profile of the cam in the negative-stiffness mechanism with the friction considered during the model design, rather than through the Taylor expansion and friction-ignoring assumption, which can avoid the approximation error between the theoretical design and the specific realization. The pure-cubic nonlinear differential equation of motion of the quasi–zero-stiffness isolator is derived and solved with the harmonic balance method, followed by the discussion of the relevant dynamic characteristics. Experimental studies are carried out based on the physical prototype of the quasi–zero-stiffness isolator. The results show that the quasi–zero-stiffness isolator can greatly extend the isolation frequency bandwidth and has a much lower resonance peak. In the low-frequency band, the quasi–zero-stiffness isolator greatly outperforms the corresponding linear system but is equivalent or even inferior in the high-frequency range with the increase of excitation force.

Design, analysis and experimental validation of high static and low dynamic stiffness mounts based on target force curves

“…11(b). Although the friction is not considered in the model design process, the friction force can be regarded as a part of the damping when the experimental results are compared with the theoretical results [29] . The static deflection of the 3rd-order HSLDS mount under the static load of the isolated mass mg is 50.5 mm (equivalent to a stiffness k e = 1195 N/m), whereas for the linear system in Fig.…”

“…12. This is because the HSLDS mount have hysteresis due to the friction of the lateral springguide-roller mechanism, which acts to increase the damping of the system as is common in HSLDS systems [29] . It can be seen from the results that the experimental resonance peak of the HSLDS mount is 1.2 Hz, with a maximum transmissibility of 2.3.…”

“…Zhou et al [28] presented a QZS vibration isolation system by using the conceptual design of cam-roller-spring mechanisms, the slideway of which is semi-circular. By replacing the slideway with a user-defined noncircular profile, Li et al [29] obtained a QZS isolator with pure-cubic restoring force. In fact, the restoring force of such a nonlinear isolator can be designed as any order, i.e.…”

Semi-active control of a new quasi-zero stiffness air suspension for commercial vehicles based on H2H∞ state feedback

“…If QZS structures are applied to the suspension field of commercial vehicles, it is expected to further greatly improve the vibration isolation performance of vehicles. Generally, QZS structures are obtained by combining a positive stiffness mechanism and a negative stiffness mechanism in parallel (Li et al, 2020). Carrella et al (2009) and Kovacic et al (2008) designed a QZS vibration isolation system based on a vertical spring with two oblique compression springs and investigated the static and dynamic characteristics.…”

An Improved Structural Analysis Method for Isolator with Quasi‐Zero‐Stiffness Characteristic

“…Besides, typical oblique coiled springs were used to provide negative stiffness. Some other forms of negative stiffness structure are proposed and studied, such as disk spring [20,21], notched flexure [22], magnetic spring [23][24][25], Euler buckled beam [26][27][28], cam roller spring [29][30][31], scissor-like structure [32][33][34], and other novel structures [35][36][37]. Different negative stiffness elements have their advantages.…”