Experimental Robustness Analysis of Magneto-Rheological Tuned Vibration Absorbers Subject to Mass Off-Tuning

2005 ◽  
Vol 128 (1) ◽  
pp. 126-131 ◽  
Author(s):  
Jeong-Hoi Koo ◽  
Mehdi Ahmadian ◽  
Mehdi Setareh
Keyword(s):  
Primary Structure ◽  
Robustness Analysis ◽  
Steel Plates ◽  
Test Apparatus ◽  
Practical Applications ◽  
Tuning Parameters ◽  
Optimal Tuning ◽  
Tuned Vibration Absorbers ◽  
Magneto Rheological ◽  
Structural Mass

This paper offers an experimental robustness analysis of a semi-active tuned vibration absorber (TVA) subject to structural mass off-tuning, which occurs frequently in practical applications of TVAs. One of the critical problems of a conventional TVA is off-tuning or miss-tuning because off-tuned TVAs may amplify the vibrations of the primary structure. This study intends to evaluate how well semi-active TVAs are able to adapt to structural mass changes (mass off-tuning) as compared with passive TVAs. To this end, a test apparatus was built to represent a two-degree-of-freedom structure model coupled with a TVA. The semi-active TVA considered in this study employed a magneto-rheological (MR) damper as its damping element to enhance overall performance. Using this test apparatus, a series of tests were conducted to identify the optimal tuning parameters of the TVAs. After obtaining each TVA’s optimal tuning parameters based on equal peak transmissibility criteria, the mass off-tuning tests were then performed on the optimally tuned TVAs. In order to off-tune the system, the mass of the primary structure varied from −19% to +19% of its nominal mass using a set of steel plates. Overall, the experimental results show that the semi-active MR TVA outperforms the passive TVA in reducing maximum vibrations. Moreover, the results show that the semi- active TVA is more robust to changes in the primary mass (mass off-tuning) The results further show that the semi-active MR TVA offers larger performance gains as the structure mass increases.

Robustness Analysis of Semi-Active Tuned Vibration Absorbers With Magneto-Rheological Dampers: An Experimental Study

2003 ◽  
Author(s):  
Jeong-Hoi Koo ◽  
Mehdi Ahmadian ◽  
Mehdi Setareh ◽  
Thomas M. Murray
Keyword(s):  
Robustness Analysis ◽  
Operating Conditions ◽  
Primary System ◽  
Test Apparatus ◽  
Practical Applications ◽  
Tuning Parameters ◽  
Optimal Tuning ◽  
Primary Mass ◽  
Frequency Changes ◽  
Magneto Rheological

This paper offers an experimental robustness analysis of a semiactive tuned vibration absorber (TVA) as well as a passive TVA. A conventional passive TVA is only effective when it is tuned properly; otherwise, it may amplify the vibrations of the primary system. In many practical applications, inevitable off-tuning of a TVA often occurs because of system’s operating conditions or parameter changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system are responsible for “off-tuning” of TVAs. When TVAs are off-tuned, their effectiveness is sharply reduced. In our experimental robustness analysis, we focused on the dynamic performance of both the passive and the semiactive TVAs when the mass of the primary system changed (mass off-tuning). To this end, a test apparatus was built to represent a two-degree-of-freedom structure model coupled with a TVA. The semiactive TVA considered in this study employed a Magneto-Rheological (MR) damper as its damping element to enhance overall performance. Using this test apparatus, a series of tests were conducted to identify the optimal tuning parameters of each of the TVAs. The optimal tuning parameters were obtained based on equal peak transmissibility criteria. The mass off-tuning tests were then performed on the optimally tuned semiactive TVA and the optimally tuned passive TVA. In order to off-tune the primary mass, the mass of the primary system varied from −23% to +23% of its nominal mass. The experimental results showed that the semiactive TVA with MR dampers are more robust to changes in the primary mass (off-tuning) than the passive TVA.

Experimental Dynamic Analysis of Magneto-Rheological Tuned Vibration Absorbers

2003 ◽  
Author(s):  
Jeong-Hoi Koo ◽  
Mehdi Ahmadian ◽  
Mehdi Setareh ◽  
Thomas M. Murray
Keyword(s):  
Active Control ◽  
Primary Structure ◽  
Control Policy ◽  
Vibration Absorbers ◽  
Control Policies ◽  
Output Displacement ◽  
Tuned Vibration Absorbers ◽  
Control Schemes ◽  
Displacement Based ◽  
Magneto Rheological

The primary purpose of this study is to experimentally evaluate the dynamics of a Magneto-Rheological Tuned Vibration Absorber (MR TVA) with several semi-active control schemes. A test rig was built to represent a two-degree of freedom primary structure model coupled with an MR TVA, and four semi-active control policies were considered. The four control policies include: velocity-based, on-off groundhook control (on-off VBG); velocity-based, continuous groundhook control (continuous VBG); displacement-based, on-off groundhook control (on-off DBG); and displacement-based, continuous groundhook control (continuous DBG). Using the test apparatus, a series of tests were conducted to investigate the dynamics of the MR TVA with each control policy. The performances of each of the cases were then analyzed along with the equivalent passive TVA. The performance index was the transmissibility between the input and the output displacement of the structure. The experimental results indicated that the MR TVA with all of the semi-active control policies, outperformed the passive TVA in reducing structural vibrations. Furthermore, the displacement-based groundhook control policies perform better in reducing the resonant vibrations of the primary structure than the velocity-based groundhook control schemes.

A Closed-Form Optimal Tuning of Mass Dampers for One Degree-of-Freedom Systems Under Rotating Unbalance Forcing

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
T. Argentini ◽  
M. Belloli ◽  
P. Borghesani
Keyword(s):  
Analytical Study ◽  
Mass Parameter ◽  
Primary System ◽  
Practical Applications ◽  
Tuning Parameters ◽  
Optimal Tuning ◽  
State Response ◽  
Optimal Damping ◽  
Mass Damper ◽  
Tuned Damper

This paper is focused on the study of a vibrating system forced by a rotating unbalance and coupled to a tuned mass damper (TMD). The analysis of the dynamic response of the entire system is used to define the parameters of such device in order to achieve optimal damping properties. The inertial forcing due to the rotating unbalance depends quadratically on the forcing frequency and it leads to optimal tuning parameters that differ from classical values obtained for pure harmonic forcing. Analytical results demonstrate that frequency and damping ratios, as a function of the mass parameter, should be higher than classical optimal parameters. The analytical study is carried out for the undamped primary system, and numerically investigated for the damped primary system. We show that, for practical applications, proper TMD tuning allows to achieve a reduction in the steady-state response of about 20% with respect to the response achieved with a classically tuned damper.

scholarly journals An Optimal Tail Selection in Risk Measurement

Risks ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 70
Author(s):  
Małgorzata Just ◽  
Krzysztof Echaust
Keyword(s):  
Mean Squared Error ◽  
Real Data ◽  
Random Variable ◽  
Threshold Level ◽  
Middle Part ◽  
Risk Measurement ◽  
Practical Applications ◽  
Tuning Parameters ◽  
Path Stability ◽  
Asymptotic Mean Squared Error

The appropriate choice of a threshold level, which separates the tails of the probability distribution of a random variable from its middle part, is considered to be a very complex and challenging task. This paper provides an empirical study on various methods of the optimal tail selection in risk measurement. The results indicate which method may be useful in practice for investors and financial and regulatory institutions. Some methods that perform well in simulation studies, based on theoretical distributions, may not perform well when real data are in use. We analyze twelve methods with different parameters for forty-eight world indices using returns from the period of 2000–Q1 2020 and four sub-periods. The research objective is to compare the methods and to identify those which can be recognized as useful in risk measurement. The results suggest that only four tail selection methods, i.e., the Path Stability algorithm, the minimization of the Asymptotic Mean Squared Error approach, the automated Eyeball method with carefully selected tuning parameters and the Hall single bootstrap procedure may be useful in practical applications.

Experimental Validation of a State-Switched Absorber Used to Control Vibrating Continuous Systems

2005 ◽  
Author(s):  
Mark Holdhusen ◽  
Kenneth A. Cunefare
Keyword(s):  
Experimental Validation ◽  
Frequency Component ◽  
Effective Bandwidth ◽  
Continuous Systems ◽  
Vibration Absorbers ◽  
Numerical Work ◽  
Tuned Vibration Absorbers ◽  
Resonance Frequencies ◽  
Magneto Rheological ◽  
The Magnetic Field

A state-switched absorber (SSA) is a device capable of instantaneously changing its stiffness, thus it can switch between resonance frequencies, increasing its effective bandwidth as compared to classical tuned vibration absorbers for vibration control. Previous numerical work has shown that an optimized SSA outperforms an optimized TVA at controlling vibrations of both a beam and a plate. This paper details the experimental validation of these simulation results. An SSA was realized by employing magneto-rheological elastomers to achieve a stiffness change. The stiffness of these elastomers is a function of the magnetic field put across them. Experiments were conducted on both a cantilever beam and a square plate clamped on all sides. Each system was excited by several two-frequency component excitations. For each forcing combination, several tuning configurations of the SSA were applied and the kinetic energy of the system was found. This observed performance was compared to the performance found through numerical simulations of a system with a similar tuning and excitation configuration. It was found that the observed performance follows closely with results found through numerical simulation.

scholarly journals A simple method for implementing Monte Carlo tests

2019 ◽  
Vol 35 (3) ◽  
pp. 1373-1392 ◽  
Author(s):  
Dong Ding ◽  
Axel Gandy ◽  
Georg Hahn
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Statistical Test ◽  
Uniform Bound ◽  
Data Set ◽  
Simple Method ◽  
Practical Applications ◽  
Tuning Parameters ◽  
Sequence Method ◽  
Uniformly Bounded

Abstract We consider a statistical test whose p value can only be approximated using Monte Carlo simulations. We are interested in deciding whether the p value for an observed data set lies above or below a given threshold such as 5%. We want to ensure that the resampling risk, the probability of the (Monte Carlo) decision being different from the true decision, is uniformly bounded. This article introduces a simple open-ended method with this property, the confidence sequence method (CSM). We compare our approach to another algorithm, SIMCTEST, which also guarantees an (asymptotic) uniform bound on the resampling risk, as well as to other Monte Carlo procedures without a uniform bound. CSM is free of tuning parameters and conservative. It has the same theoretical guarantee as SIMCTEST and, in many settings, similar stopping boundaries. As it is much simpler than other methods, CSM is a useful method for practical applications.

scholarly journals Regulating the Expansion Characteristics of Cementitious Materials Using Blended MgO-Type Expansive Agent

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 976 ◽  
Author(s):  
Peng Liu ◽  
Zhiyang Chen ◽  
Min Deng
Keyword(s):  
Stress Test ◽  
Cementitious Materials ◽  
Test Apparatus ◽  
Early Type ◽  
Late Type ◽  
Cement Pastes ◽  
Practical Applications ◽  
Expansive Agent

To promote the application of MgO-type expansive agents (MEAs), the expansion stresses produced by compacted MEAs with different activities cured in water at 40 °C were measured using a self-designed expansion stress test apparatus. Based on these, different MEAs were divided into the early-type MgO expansive agent and the late-type MgO expansive agent classifications according to the stress curves of compacted MEAs. The two types of MEAs were blended with each other at different ratios and added into cement pastes. Results indicated that the expansion of the cement pastes added with blended MEAs lasted from the beginning to 200 days later, and the expansion characteristics can be regulated by adjusting the blending ratio of MEAs and the choice of types of MEAs. The results suggest that the expansion of MEAs can be improved by using blended MEAs in practical applications.

Fuzzy Controller Design Used for Steel Length Measurement

2011 ◽  
Vol 383-390 ◽  
pp. 5176-5181
Author(s):  
Chong Sheng Hou
Keyword(s):  
Control System ◽  
Fuzzy Control ◽  
Steel Plate ◽  
Fuzzy Controller ◽  
Controller Design ◽  
Steel Plates ◽  
Control Technology ◽  
Practical Applications ◽  
Learning Function ◽  
Self Learning

The accurate measurement of the length of steel plate is the key to control technology for cross-cutting production line. Three steel plates determining-length control algorithms were deeply analyzed, in the set-length control strategy fuzzy control technology was introduced, and determining-length fuzzy controller structure and realization was analyzed; In order to improve the accuracy of steel plate crosscut, on the basis of the fuzzy control system self-learning function and artificial self-learning function were increased. Practical applications show that technical advancement, reliability of the control system and shear plate accuracy are high, fully meet the requirements of control.

Passive, Adaptive and Active Tuned Vibration Absorbers—A Survey

1995 ◽  
Vol 117 (B) ◽  
pp. 234-242 ◽  
Author(s):  
J. Q. Sun ◽  
M. R. Jolly ◽  
M. A. Norris
Keyword(s):  
Recent Progress ◽  
Noise Suppression ◽  
Vibration Absorbers ◽  
Optimal Tuning ◽  
Tuned Vibration Absorbers ◽  
On Line ◽  
Fail Safe

An overview of the recent development of tuned vibration absorbers (TVAs) for vibration and noise suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and presents some contemporary applications of passive TVAs. Furthermore, the paper also presents a brief discussion on the recent progress of adaptive and semi-active TVAs along with their on-line tuning strategies, and active and hybrid fail-safe TVAs.

Experimental Vibration Control of a Two-Degree of Freedom, State-Switched Absorber System

2002 ◽  
Author(s):  
Mark H. Holdhusen ◽  
Kenneth A. Cunefare
Keyword(s):  
Vibration Control ◽  
Vibration Suppression ◽  
Effective Bandwidth ◽  
Vibration Absorbers ◽  
Lumped Mass ◽  
Tuned Vibration Absorbers ◽  
Resonance Frequencies ◽  
Magneto Rheological ◽  
Theoretical Simulations ◽  
Two Degree Of Freedom

A State-Switched Absorber (SSA) is a device capable of instantaneously changing its stiffness, thus it can switch between resonance frequencies, increasing its effective bandwidth as compared to classical tuned vibration absorbers for vibration control. Previous theoretical simulations show that for a system subjected to a multi-harmonic disturbance, using an appropriate logic for switching states, the SSA reduces vibration more effectively than classical tuned vibration absorbers (TVA). This paper considers the experimental performance of the SSA for vibration suppression of an elastically mounted lumped mass base. State switching is achieved using magneto-rheological fluid to connect or disconnect a coil spring in parallel with other coil springs. The stiffness state is controlled by applying or removing a magnetic field across of the MR fluid. Experiments were performed over a range of forcing and tuning frequencies. The SSA system, optimally tuned, outperformed the optimal classical TVA system for all combinations of forcing frequencies.

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