Resonance Characteristics of Unidirectional Viscous and Coulomb-Damped Vibration Isolation Systems

1967 ◽  
Vol 89 (4) ◽  
pp. 729-740 ◽  
Author(s):  
Jerome E. Ruzicka
Keyword(s):  
Resonant Frequency ◽  
Vibration Isolation ◽  
Elementary Theory ◽  
Rate Of Change ◽  
Design Data ◽  
Isolation System ◽  
Extensive Evaluation ◽  
Wide Range ◽  
Isolation Systems ◽  
Damped Systems

Elementary vibration theory based on transfer response analyses of single-degree-of-freedom systems indicates that an increase in isolation system damping causes a decrease in resonant transmissibility. This theory further specifies that, for viscous-damped systems, an increase in damping decreases the resonant frequency whereas, for Coulomb-damped systems, an increase in damping increases the resonant frequency. It is frequently found in practice that an increase in damping may increase the resonant transmissibility and cause a change in resonant frequency opposite to that predicted by elementary theory. This paper presents a more extensive evaluation of the resonance characteristics of unidirectional vibration isolation systems, including the effects of directly coupled and elastically coupled damping elements. Mathematical models and absolute transmissibility characteristics of viscous and Coulomb-damped vibration isolation systems are discussed and resonance characteristics are analyzed in terms of the resonant frequency ratio, the resonant transmissibility, and the rate of change of these parameters with damping. Design data are presented graphically for parametric variations of stiffness and damping which are sufficiently broad to encompass a wide range of practical engineering problems.

Theoretical and Experimental Investigation of Electrohydraulic Vibration Isolation Systems

1969 ◽  
Vol 91 (4) ◽  
pp. 981-990 ◽  
Author(s):  
Dale W. Schubert ◽  
Jerome E. Ruzicka
Keyword(s):  
Vibration Isolation ◽  
Broad Band ◽  
System Stability ◽  
Automatic Frequency ◽  
Hydraulic Actuator ◽  
Isolation System ◽  
Response Characteristics ◽  
Wide Range ◽  
Isolation Systems ◽  
System Configurations

This paper presents the results of an investigation of electrohydraulic vibration isolation systems that employ multiple electronic feedback signals to control the action of a hydraulic actuator in a closed-loop servocontrol system. The theoretical basis for the operation of the isolation system is discussed, including consideration of system stability. Experimental data are provided for unidirectional single-mass isolation system configurations that provide limited-band isolation, broad-band isolation, single-notch isolation, combined notch and broad-band isolation, multiple-notch isolation, and notch isolation with automatic frequency tracking. The results emphasize the unique performance characteristics of electrohydraulic isolation systems, including isolation of ultralow-frequency vibration, zero static and steady-state relative deflections, response substantially independent of the weight of the isolated body, and the ability to tailor the frequency-response characteristics to satisfy a wide range of specific requirements.

Design and analysis of a vibration isolation system with cam–roller–spring–rod mechanism

2021 ◽  
pp. 107754632110005
Author(s):  
Yonglei Zhang ◽  
Guo Wei ◽  
Hao Wen ◽  
Dongping Jin ◽  
Haiyan Hu
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Experimental Studies ◽  
Excitation Amplitude ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Stiffness Characteristic ◽  
Negative Stiffness Mechanism ◽  
Isolation Systems ◽  
Vibration Isolation Performance

The vibration isolation system using a pair of oblique springs or a spring-rod mechanism as a negative stiffness mechanism exhibits a high-static low-dynamic stiffness characteristic and a nonlinear jump phenomenon when the system damping is light and the excitation amplitude is large. It is possible to remove the jump via adjusting the end trajectories of the above springs or rods. To realize this idea, the article presents a vibration isolation system with a cam–roller–spring–rod mechanism and gives the detailed numerical and experimental studies on the effects of the above mechanism on the vibration isolation performance. The comparative studies demonstrate that the vibration isolation system proposed works well and outperforms some other vibration isolation systems.

scholarly journals Analysis and design of the power law damping based on the nonlinear vessel isolation system

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881719 ◽  
Author(s):  
You Wang ◽  
Xinghua Zhu ◽  
Rong Zheng ◽  
Zhe Tang ◽  
Bingbing Chen
Keyword(s):  
Resonant Frequency ◽  
Working Conditions ◽  
Power Law ◽  
Nonlinear Damping ◽  
Frequency Region ◽  
Isolation System ◽  
Analysis And Design ◽  
Force Transmissibility ◽  
Isolation Systems ◽  
Isolation Performance

In this study, the applications of the cubic power law damping in vessel isolation systems are investigated. The isolation performance is assessed using the force transmissibility of the vessel isolation system, which is simplified as a multiple-degree-of-freedom system with two parallel freedoms. The force transmissibilities of different working conditions faced in practice are discussed by applying the cubic power law damping on different positions of the vessel isolation system. Numerical results indicate that by adding the cubic power law damping to an appropriate position, the isolation system can not only suppress the force transmissibility over the resonant frequency region but also keep the force transmissibility unaffected at the nonresonant frequency region. Moreover, the design of the nonlinear vessel isolation system is discussed by finding the optimal nonlinear damping of the isolation system.

Modeling and Control Analysis of a 3-PUPU Dual Compliant Parallel Manipulator for Micro Positioning and Active Vibration Isolation

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Y. Yun ◽  
Y. Li
Keyword(s):  
Vibration Control ◽  
Parallel Manipulator ◽  
Vibration Isolation ◽  
Active Vibration Control ◽  
Parallel Robots ◽  
Control Analysis ◽  
Isolation System ◽  
Wide Range ◽  
Active Vibration ◽  
Active Vibration Isolation

In recent years, many applications in precision engineering require a careful isolation of the instrument from the vibration sources by adopting active vibration isolation system to achieve a very low remaining vibration level, especially for the very low frequency under 10 Hz vibration signals. This paper presents a 3-PUPU dual parallel manipulator for both rough positioning and active vibration isolation in a wide-range workspace based on our previous research experiences in the systematical modeling and study of parallel robots. The manipulator is designed as a kind of macro/micro hybrid robot. Both the kinematics model for macro motion and dynamics model for micro motion are established by using stiffness equation and the Kane’s method, respectively. An active vibration control strategy is described by using the H2 method. Moreover, numerical simulations on the inverse solution for macro motion, workspace, and the active vibration control effects are performed at the end of this paper.

Recent Advances in Quasi-Zero-Stiffness Vibration Isolation Systems

2013 ◽  
Vol 397-400 ◽  
pp. 295-303 ◽  
Author(s):  
Fu Niu ◽  
Ling Shuai Meng ◽  
Wen Juan Wu ◽  
Jing Gong Sun ◽  
Wei Hua Su ◽  
...  
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Future Research ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Significant Development ◽  
Recent Advances ◽  
Low Frequency Vibration ◽  
Future Research Directions ◽  
Isolation Systems

The quasi-zero-stiffness vibration isolation system has witnessed significant development due to the pressing demands for low frequency and ultra-low frequency vibration isolation. In this study, the isolation theory and the characteristic of the quasi-zero-stiffness vibration isolation system are illustrated. Based on its implementation mechanics, a comprehensive assessment of recent advances of the quasi-zero-stiffness vibration isolation system is presented. The future research directions are finally prospected.

Friction Damping and Isolation Systems

1995 ◽  
Vol 117 (B) ◽  
pp. 196-206 ◽  
Author(s):  
A. A. Ferri
Keyword(s):  
Energy Dissipation ◽  
System Performance ◽  
Dry Friction ◽  
Vibration Isolation ◽  
Analytical Techniques ◽  
Experimental Treatment ◽  
Structural Systems ◽  
Friction Damping ◽  
Isolation Systems ◽  
Damped Systems

This paper surveys the literature on the use of dry friction in passive damping and vibration isolation. Several analytical techniques are presented followed by applications from various areas. Despite difficulties in the analytical and experimental treatment of friction damped systems, numerous studies have endeavored to predict, measure, and/or enhance the energy dissipation and vibration isolation properties of dry friction in order to improve system performance. Undoubtedly, friction damping will continue to play an important role in many mechanical and structural systems.

A Bidirectional-Controllable Magnetorheological Energy Absorber for Shock and Vibration Isolation Systems

2012 ◽  
Author(s):  
Xian-Xu Bai ◽  
Norman M. Wereley ◽  
Wei Hu ◽  
Dai-Hua Wang
Keyword(s):  
Mechanical Model ◽  
Vibration Isolation ◽  
Dynamic Force ◽  
Damping Force ◽  
Isolation System ◽  
Isolation Systems ◽  
Force Range ◽  
Fail Safe ◽  
Safe Performance ◽  
Vibration Isolation Performance

Semi-active shock and vibration isolation systems using magnetorheological energy absorbers (MREAs) require minimization of the field-off damping force at high speed. This is because the viscous damping force for high shaft speed become excessive. This implies that the controllable dynamic force range, defined as the ratio of the field-on damping force to the field-off damping force, is dramatically reduced. In addition, fail-safe MREA performance, if power were to be lost, is of great importance to shock and vibration isolation systems. A key design goal is to minimize field-off damping force while maximizing MREA dynamic force, while maintaining fail-safe performance. This study presents the principle of a bidirectional-controllable MREA that can produce large damping force and dynamic force range, as well as excellent fail-safe performance. The bidirectional-controllable MREA is configured and its hydro-mechanical model is theoretically constructed. From the hydro-mechanical model, the mathematical model for the MREA is established using a Bingham-plastic nonlinear fluid model. The characteristics of the MREA are theoretically evaluated and compared with those of a conventional flow-mode MREA with an identical volume. In order to investigate the feasibility and capability of the bidirectional-controllable MREA in the context of the semi-active shock and vibration isolation systems, a mechanical model of a single-degree-of-freedom (SDOF) isolation system using a bidirectional-controllable MREA is constructed and the governing equation for the SDOF isolation system is derived. A skyhook control algorithm is utilized to improve the shock and vibration isolation performance of the isolation systems. Simulated vibration isolation performance using bidirectional-controllable and conventional MREAs under shock loads due to vertical impulses (the initial velocity is as high as 10 m/s), and sinusoidal vibrations, are evaluated, compared, and analyzed.

Optimization of Pneumatic Vibration Isolation System for Vehicle Suspension

1978 ◽  
Vol 100 (3) ◽  
pp. 500-506 ◽  
Author(s):  
E. Esmailzadeh
Keyword(s):  
Vibration Isolation ◽  
Load Capacity ◽  
Damping Ratio ◽  
Optimization Technique ◽  
Suspension System ◽  
The Body ◽  
Vehicle Suspension ◽  
Design Data ◽  
General Outline ◽  
Wide Range

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.

On the Performance of a Two-Stage Vibration Isolation System Which has Geometrically Nonlinear Stiffness

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Zeqi Lu ◽  
Tiejun Yang ◽  
Michael J. Brennan ◽  
Xinhui Li ◽  
Zhigang Liu
Keyword(s):  
Resonance Frequency ◽  
Vibration Isolation ◽  
Low Frequency ◽  
Single Stage ◽  
Nonlinear Stiffness ◽  
Two Stage ◽  
Isolation System ◽  
Beneficial Effects ◽  
Isolation Systems ◽  
The Right

Linear single-stage vibration isolation systems have a limitation on their performance, which can be overcome passively by using linear two-stage isolations systems. It has been demonstrated by several researchers that linear single-stage isolation systems can be improved upon by using nonlinear stiffness elements, especially for low-frequency vibrations. In this paper, an investigation is conducted into whether the same improvements can be made to a linear two-stage isolation system using the same methodology for both force and base excitation. The benefits of incorporating geometric stiffness nonlinearity in both upper and lower stages are studied. It is found that there are beneficial effects of using nonlinearity in the stiffness in both stages for both types of excitation. Further, it is found that this nonlinearity causes the transmissibility at the lower resonance frequency to bend to the right, but the transmissibility at the higher resonance frequency is not affected in the same way. Generally, it is found that a nonlinear two-stage system has superior isolation performance compared to that of a linear two-stage isolator.

scholarly journals INCREASED VIBRATION ON REFRIGERATOR SHIPS OF B437/11 PROJECT AND TECHNICAL PROPOSALS ON ITS REDUCTION

2018 ◽  
pp. 58-69
Author(s):  
Minas Armenakovich Minasyan ◽  
Aung Myo Thant ◽  
Armen Minasovich Minasyan
Keyword(s):  
Service Life ◽  
Vibration Isolation ◽  
Steel Wire ◽  
Modern Technology ◽  
Wire Rope ◽  
Diesel Generator ◽  
Vibration Isolators ◽  
Wide Range ◽  
Isolation Systems ◽  
The Impact

The paper considers the causes of increased vibration of four auxiliary diesel-generator sets of "Sulzer" 5АL25 type on board nine refrigerated vessels of B437 / 11 project after 15 years of operation. The proposed wide range of possible applications to address the problem of high vibration of diesel generators and motor vessels there were generally implemented upgraded turbocharger brackets, engine sub-frame and supporting spiral-rope vibration isolators in the shock absorption system of the diesel-generator. Four original patented technical solutions have been presented, among which one solution is implemented in 5AL25 diesel generator and 2H 8.5/11 diesel damping systems. There has been offered wide application both wire rope vibration isolators and combined isolators, in which elastic elements are made of nonflammable materials. Wire rope vibration isolators combine high bearing capacity (static loads within 1 N - 50 kN) with high elasticity under dynamic effects; their natural frequencies can drop to 2.5 Hz. Under the worst conditions 75% of the free moving weakens the impact to values that ensure the necessary safety of the object. Experience in designing vibration isolation systems allows to set the maximum range of loads within 15 - 25 g. The vibration isolators made of steel wire rope are practically not affected by the environment, they are made of stainless steel. They effectively operate at temperatures -200°C - +370°C in the presence of oil, dirt, sand, salt fog, etc. They usually have a service life comparable with the service life of the insulated object. Wire rope vibration isolators and combined vibration isolators can be used in all fields of modern technology: shipbuilding, power engineering, automotive, aviation and space industries, etc.

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