Pneumatic Vibration Isolation System Research Articles

Research on the Pressure Regulator Effect on a Pneumatic Vibration Isolation System

The pneumatic vibration isolator (PVI) plays an increasingly important role in precision manufacturing. In this paper, aiming to detect the performance of the pressure regulator in the PVI system, a PVI testing system with a pressure regulator is designed and developed. Firstly, the structure of the pneumatic spring is presented and analyzed, and the nonlinear stiffness is obtained based on the ideal gas model and material mechanics. Then, according to the working principle and continuity equations of ideal airflow, a dynamic model of the PVI system with a pressure regulator is established. Through the simulation analysis, the vibration isolation performance is improved with the efficient and precise pressure regulator. The average values of both the vibration velocity and transmission rate decrease when the vibration is set to 4, 10, 20 and 40 Hz, respectively. The experiments demonstrate the reliability and effectiveness of the pressure regulator. This achievement will become an important basis for future research concerning precision manufacturing.

Active pneumatic vibration isolation system using negative stiffness structures for a vehicle seat

Abstract In this paper, an active pneumatic vibration isolation system using negative stiffness structures (NSS) for a vehicle seat in low excitation frequencies is proposed, which is named as an active system with NSS. Here, the negative stiffness structures (NSS) are used to minimize the vibratory attraction of a vehicle seat. Owing to the time-varying and nonlinear behavior of the proposed system, it is not easy to build an accurate dynamic for model-based controller design. Thus, an adaptive intelligent backstepping controller (AIBC) is designed to manage the system operation for high-isolation effectiveness. In addition, an auxiliary control effort is also introduced to eliminate the effect of the unpredictable perturbations. Moreover, a radial basis function neural network (RBFNN) model is utilized to estimate the optimal gain of the auxiliary control effort. Final control input and the adaptive law for updating coefficients of the approximate series can be obtained step by step using a suitable Lyapunov function. Afterward, the isolation performance of the proposed system is assessed experimentally. In addition, the effectiveness of the designed controller for the proposed system is also compared with that of the traditional backstepping controller (BC). The experimental results show that the isolation effectiveness of the proposed system is better than that of the active system without NSS. Furthermore, the undesirable chattering phenomenon in control effort is quite reduced by the estimation mechanism. Finally, some concluding remarks are given at the end of the paper.

Active suppression of pneumatic vibration isolators using adaptive sliding controller with self-tuning fuzzy compensation

This paper develops intelligent control schemes for a diaphragm-type pneumatic vibration isolation system. The active-control schemes are applied to the pneumatic isolator to enhance isolation performances in the low-frequency range where passive techniques usually have difficulties in remaining effective, especially at the resonance frequency. The functional approximation technique (FAT) is integrated with a sliding-mode control (SMC) design to capture unknown system dynamics and release the requirement of mathematical modeling. To deal with approximation error and system dynamics variation, an adaptive fuzzy sliding-mode controller (AFSMC) is employed as a compensator of the FAT-based SMC. Lyapunov stability theory is used not only to ensure the closed-loop stability, but also to formulate the updating laws for weighting coefficients of expansion basis and fuzzy tuning parameters. To validate the proposed method, a composite control scheme using pressure and velocity measurements as feedback signals is implemented. Experimental explorations indicate that isolation performances obtained using the proposed FAT-based sliding control augmented with AFSMC compensation (FA + AFSMC) are evidently better than those of the traditional proportional integral-derivative control and solely AFSMC scheme.

이동 질량을 포함하는 능동형 공압제진대에 대한 시간지연제어기법의 적용 검토

As applying an active control technique to a pneumatic vibration isolation system, the settling time for the payload excitation could be remarkably reduced as well as the improvement of isolation performance for the ground vibration. Some previous researches were dealt with the settling time through the simulation or experiment but, the discussion on the simulation or experimental results including moving parts, such as a XY-stage, on the isolation table rarely exists. As considering the moving part, the dynamic model could be time varying system and in such a case the force imposed on pneumatic vibration isolation table could be described by inertial forces of moving parts according to Newton's 3rd law, the action and reaction law. In this paper, the simulation procedure of the 3-DOF active pneumatic vibration isolation system including moving parts by TDC(time delay control) technique is proposed and the effectiveness through simulation results are also shown.

Modeling and analysis of dual-chamber pneumatic spring with adjustable damping for precision vibration isolation

Dual-chamber pneumatic spring with adjustable damping (DCPS-AD) employs a variable orifice mechanism (VOM) to obtain the adjustable stiffness and damping characteristics. These adjustable characteristics are aimed at improving the performance of the pneumatic vibration isolation system (VIS). In order to understand thoroughly how the adjustable parameter of VOM affects the behavior of DCPS-AD, the model of DCPS-AD is derived analytically and validated experimentally. The influence of VOM on the performance of DCPS-AD is analyzed quantitatively. All the results demonstrate that VOM has the ability to vary complex stiffness distribution in frequency domain. Based on these results, the approach optimizing the performance of VIS is proposed, which is realized by adjusting VOM actively. Performance experimental measurements of VIS in frequency domain are carried out under different payload masses. The measurement results validate the proposed approach, which can optimize the performance of VIS when some application conditions varying.

Investigation on Harmonic Response of Pneumatic Vibration Isolation System with Single and Double-Frequency Excitations

In this paper, a nonlinear model of pneumatic vibration isolator was established, considering the volumetric compressibility of air. Based on this, simulation analyses were done using matlab/simulink software. The response to two different types of disturbances is studied: single-frequency excitation and double-frequency excitation. Single-frequency excitation can induce harmonic frequency response and offset response at the zero frequency. When the frequency is near to the the linearized natural frequency, the harmonic frequency response become stronger. Nonlinear characters have much to do with the drive amplitude. When the drive amplitude become large, the nonlinear characters are more obvious. Double-frequency excitation can induce combination resonance. When the two drive frequencys are close, combination resonance are more strong.

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

This paper aims at accurate modeling and sensitivity analysis for a pneumatic vibration isolation system (PVIS) as a foundation for practical design. Even though the PVIS is widely used for its effective performance in vibration isolation, its design has depended largely on trial-and-error methods. In previous studies, nonlinear characteristics of the diaphragm and the air flow restrictor, which significantly affect the performance of a PVIS, have been investigated. However, several hurdles, such as the absence of a mathematical model for the diaphragm, still remain with regard to the model-based prediction of performance. Therefore, a fractional derivative model for the diaphragm and a quadratic damping model for the air flow restrictor are newly developed based on the careful examination of previous studies. Then, sensitivities of vibration isolation performance indices with regard to major design variables are analyzed and new approximation formulas are created based on the dynamic characteristics of the PVIS. Our models with a transmissibility-computing algorithm are verified by comparison with experimental data. The sensitivity analyses and approximation formulas are expected to be useful for practical PVIS design owing to their simplicity and accuracy.

Pneumatically Isolated Inertia Base with Active Damping for a Transmission Electron Microscope (TEM)

Low frequency sound and vibration affects the performance and use of electron microscopes, by disturbing the stability and resolution of the specimen's video image. A transmission electron microscope (TEM) addition was proposed to an existing research suite that had three scanning electron microscopes (SEM). The TEM, which is very heavy, rather tall and has a high center of gravity, is very sensitive to floor vibrations. This case study presents sources of disturbing vibration with spectrum measurements. The designs of the microscope room and an actively damped, pneumatic vibration isolation system are discussed. Post-installation vibration measurement results to validate performance are presented in spectral analysis charts versus criteria. Drawings and photographs illustrate the installation.

Modeling and Verification of an Innovative Active Pneumatic Vibration Isolation System

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.

Optimization of Pneumatic Vibration Isolation System for Vehicle Suspension

The suspension system of a vehicle provides the means by which forces and movements are transferred from the body to the wheels and vice versa. While the general outline of vehicle suspension behavior is fairly well known, little interest has been shown in the detailed dynamic performance of the various components. Air springs are perhaps the most versatile and adaptable type of suspension element. They provide practically frictionless action, adjustable load capacity and simplicity of height control. Initially, a vehicle suspension system with a pneumatic isolator connected to a fixed volume tank via parallel plate restrictor is considered. Here the damping is provided by the flow of air through the restricted passage which has an advantage over the conventional viscous shock absorber. Body movements are only considered to be vertical harmonic displacement. An optimization technique is applied to evaluate the optimum values of many parameters involved for which the maximum transmitted motion to the body would be minimum over the broad frequency range. Theoretical expressions for the transmissibility of the body and the wheel, optimum values of mass ratio, stiffness ratio and damping ratio are presented. Design data are presented nondimensionally for parameter variations which are sufficiently broad to encompass a wide range of practical engineering problems.