Modeling and Verification of an Innovative Active Pneumatic Vibration Isolation System

Abstract

This paper presents a novel concept in active pneumatic vibration isolation. The novelty in the concept is in utilizing an air-spring-orifice-accumulator combination to vary the natural frequency as well as inject damping into the system per requirement, thereby eliminating the need for a hydraulic cylinder or a magnetorheological damper. This continuously variable natural frequency and damping (CVNFD) technology is aimed at achieving active vibration isolation. For analysis purposes, a particular application in the form of pneumatic seat suspension for off-road vehicles is chosen. A mathematical model representing the system is derived rigorously from inertial dynamics and first principles in thermodynamics. Empirical corelations are also used to include nonlinearities such as friction that cannot be accounted for in the thermodynamic equations. An exhaustive computational study is undertaken to help understand the physics of the system. The computational study clearly depicts the CVNFD capability of the vibration isolation system. An experimental test rig is built to experimentally validate analytical and simulation modeling of the system. Experimental verification corroborated the variable natural frequency and damping characteristic of the system observed through computational simulations.

Notice of Retraction: Nonlinearity analyses of pneumatic vibration isolation system with simple harmonic excitations

“…An overwhelming majority of researches were done under the assumptions of linearity by small amplitude, and the pneumatic vibration isolation system were often simplified as spring-damper-mass system. Under the condition of large amplitude, the nonlinear influence of air spring was often simplified as the change of stiffness coefficient and natural vibration frequency of the air spring [5][6]. In the area of active control this linear model is also used often [7].…”

Modeling and sensitivity analysis of a pneumatic vibration isolation system with two air chambers

“…(22) and (23) by A p and substituting Eqs. (11) and (16) into the result, the equivalent elastic forces caused by the damping and spring chambers can be expressed as…”

“…Some previous studies regarded the flow restrictor as a linear damper, in which case the transfer function of the PVIS is easily formulated [12,14,18]. However, the nonlinearity of the damping characteristics of the flow restrictor was demonstrated in many studies [11,[19][20][21]. Lee and Kim [13] advanced the analysis of a PVIS by considering the flow restrictor as a nonlinear damper.…”

“…Vibration isolation performance enhancement of the PVIS has been attempted by a variety of ways such as reshaping of elastomeric diaphragm [4], usage of an air flow restrictor of porous media [5], energy dissipation by a gimbal piston in oil chamber [6], parallelization with a negative-stiffness device [7] and adoption of active control schemes [8][9][10][11]. In all those attempts, the basic work is the modeling of components of the PVIS since effects of design variables on vibration isolation performance can be predicted only with accurate mathematical models and corresponding computational techniques.…”

Nonlinear primary resonances of a pneumatic spring under simple harmonic excitations

“…Compared to mechanical or electromechanical devices, pneumatic isolators combine the ability to support large masses with a small stiffness characteristic, so pneumatic vibration isolation system is widely used [1][2][3][4][5][6][7]. Because of the complexity of nonlinear dynamical systems, the nonlinear influence of elastic restoring force was not studied as the development of pneumatic vibration isolation system.…”