Enhancing Vibration Isolation Performance by Exploiting Novel Spring-Bar Mechanism

Abstract

This study investigates the use of a spring-bar mechanism (SBM) in a vibration suppression system to improve its performance. The SBM, comprising bars and springs, is configured with a conventional linear spring-damper isolator unit. The dynamic response, force transmissibility, and vibration energy flow behaviour are studied to evaluate the vibration suppression performance of the integrated system. It is found that the SBM can introduce hardening, softening stiffness, or double-well potential characteristics to the system. By tuning the SBM parameters, constant negative stiffness is achieved so that the natural frequency of the overall system is reduced for enhanced low-frequency vibration isolation. It is also found that the proposed design yields a wider effective isolation range compared to the conventional spring-damper isolator and a previously proposed isolator with a negative stiffness mechanism. The frequency response relation of the force-excited system is derived using the averaging method and elliptical functions. It is also found that the system can exhibit chaotic motions, for which the associated time-averaged power is found to tend to an asymptotic value as the averaging time increases. It is shown that the time-averaged power flow variables can be used as uniform performance indices of nonlinear vibration isolators exhibiting periodic or chaotic motions. It is shown that the SBM can assist in reducing force transmission and input power, thereby expanding the frequency range of vibration attenuations.

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

“…Hence, the lower ends of the straight bar (19) could rotate circularly by means of a pin (20), while the upper ends could freely slide along the surface of the upper plate (7). Furthermore, two air bellows (15) were installed between the left link (14) and the right link (16). One side of the air bellows (15) was connected with a bellows fork (13), and the other side was connected with the crisscross mechanism by using a rotating joint (17).…”

“…This joint could move up and down while slipping on the bellows' linear guide (18). Finally, a negative-stiffness structure consisted of the air bellows (15), the bellows fork (13), the left link (14), and the right link (15), which produced a negative stiffness in the vertical direction. The schematic diagram of the ASVIS in the static equilibration position is described in Figure 1b.…”

“…A nonlinear vibration isolation system with an NSS was investigated in terms of dynamics and power flow by J. Yang et al [13]. Shi et al [14] suggested to use a novel spring bar mechanism to improve the vibration isolation performance of the NSS. Moreover, other researchers designed vibration isolation systems that used a cam-roller mechanism combined with negative-stiffness elements [15].…”