Dynamic Modeling and Vibration Control of Electrorheological Mounts

2004 ◽  
Vol 126 (4) ◽  
pp. 537-541 ◽  
Author(s):  
Seung-Bok Choi ◽  
Sung-Ryong Hong
Keyword(s):  
Vibration Control ◽  
Frequency Domain ◽  
Dynamic Modeling ◽  
Static Load ◽  
Equations Of Motion ◽  
The Other ◽  
Flow Mode ◽  
Governing Equations ◽  
Field Dependent ◽  
Different Types

This paper presents two different types of electrorheological (ER) mounts that can support a static load of 200 kg. One is a flow mode type, and the other is a squeeze mode type. After analyzing the governing equations of motion, two ER mounts are designed and manufactured. The field-dependent displacement transmissibilities are evaluated in the frequency domain. In addition, vibration control responses of two ER mounts are experimentally investigated by implementing a skyhook controller.

Active Vibration Control of Smart Hull Structure Using Piezoelectric Composite Actuators

2008 ◽  
Vol 47-50 ◽  
pp. 137-140 ◽  
Author(s):  
Jung Woo Sohn ◽  
Seung Bok Choi
Keyword(s):  
Vibration Control ◽  
Fiber Composite ◽  
Equations Of Motion ◽  
Active Vibration Control ◽  
Piezoelectric Composite ◽  
Governing Equations ◽  
Linear Quadratic ◽  
Element Analysis ◽  
Hull Structure ◽  
Active Vibration

In this paper, active vibration control performance of the smart hull structure with Macro-Fiber Composite (MFC) is evaluated. The governing equations of motion of the hull structure with MFC actuators are derived based on the classical Donnell-Mushtari shell theory. Subsequently, modal characteristics are investigated and compared with the results obtained from finite element analysis and experiment. The governing equations of vibration control system are then established and expressed in the state space form. Linear Quadratic Gaussian (LQG) control algorithm is designed in order to effectively and actively control the imposed vibration. The controller is experimentally realized and control performances are evaluated.

Dynamic Modeling and Vibration Control of a Space Flexible Manipulator Using Piezoelectric Actuators and Sensors

2011 ◽  
Vol 345 ◽  
pp. 46-52 ◽  
Author(s):  
Jun Qiang Lou ◽  
Yan Ding Wei
Keyword(s):  
Vibration Control ◽  
Dynamic Modeling ◽  
Vibration Suppression ◽  
Equations Of Motion ◽  
Linear Quadratic Regulator ◽  
Flexible Manipulator ◽  
Coupled Vibration ◽  
Linear Quadratic ◽  
Space Manipulator ◽  
Tip Mass

This paper concerns the dynamic modeling and vibration control of a space two-link flexible manipulator. Two types of PZT actuators, PZT shear actuator and torsional actuator, are used to suppress the bending-torsional-coupled vibration of the space manipulator. Using extended Hamilton’s principle and the finite element method, equations of motion of the space flexible manipulator with PZT actuators and tip mass are obtained. Based on modal analyze theory, the state space model of the system is then used to design the control system. A linear quadratic regulator (LQR) controller is designed to achieve vibration suppression of the space manipulator system. From the numerical results, we can get that the proposed controller has a suitable and efficient performance suppressing the bending-torsional-coupled vibration of the space two-link flexible manipulator.

scholarly journals A Novel Elastic Metamaterial with Multiple Resonators for Vibration Suppression

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Saman Ahmadi Nooraldinvand ◽  
Hamid M. Sedighi ◽  
Amin Yaghootian
Keyword(s):  
Vibration Suppression ◽  
Equations Of Motion ◽  
Small Mass ◽  
The Other ◽  
Governing Equations ◽  
System Parameters ◽  
Rectangular Frame ◽  
Adams Software ◽  
Linear Spring ◽  
Base Structure

In this paper, two models of elastic metamaterial containing one and two resonators are proposed to obtain the bandgaps with the aim of providing broadband vibration suppression. The model with one DOF is built by assembling several unite cells in which each unite cell consists of a rectangular frame as the base structure and a rack-and-pinion mechanism that is joined to the frame with a linear spring on both sides. In the second model with two DOF, a small mass is added while its center is attached to the center of the pinion on one side and the other side is connected to the rectangular frame via a linear spring. In the first mechanism, the pinion is considered as the single resonator, and in the 2DOF model, on the other hand, the pinion and small mass acted as multiple resonators. By obtaining the governing equations of motion for a single cell in each model, the dynamic behavior of two metastructures is thoroughly investigated. Therefore, the equations of motion for the two models are written in matrix form, and then, the dispersion relations are presented to analyze the influences of system parameters on the bandgaps’ starting/ending frequencies. Finally, two models are successfully compared and then numerically simulated via MATLAB-SIMULINK and MSC-ADAMS software. With the aid of closed-form expressions for starting/ending frequencies, the correlation between the system parameters and bandgap intervals can be readily recognized.

Dynamic Modeling of Underway Ship-to-Ship Operations

2011 ◽  
Author(s):  
Carlos Eduardo Silva de Souza ◽  
Helio Mitio Morishita
Keyword(s):  
Dynamic Model ◽  
Dynamic Modeling ◽  
Hydrodynamic Interaction ◽  
Equations Of Motion ◽  
Wave Interaction ◽  
Memory Effects ◽  
The Other ◽  
Transfer Phase ◽  
Mooring Lines

A dynamic model for underway ship-to-ship operations with surge velocity is developed. It is admitted that one ship develops power ahead, towing the other vessel together. Models for all relevant loads involved in such operation are present, like environment, mooring, fenders and hydrodynamic interaction loads. The equations of motion take fluid memory effects and wave interaction into account. The model was implemented and simulations were carried out, focusing in the transfer phase of a STS operation. The results are used to analyze mooring lines loads, which is a useful tool for mooring schemes design.

Vibration Control of Beams with Negative Capacitive Shunting of Interdigital Electrode Piezoceramics

2005 ◽  
Vol 11 (3) ◽  
pp. 331-346 ◽  
Author(s):  
Chul H. Park ◽  
Amr Baz
Keyword(s):  
Mathematical Model ◽  
Boundary Conditions ◽  
Vibration Control ◽  
Equations Of Motion ◽  
Vibration Modes ◽  
Frequency Range ◽  
Governing Equations ◽  
Interdigital Electrode ◽  
Beam System ◽  
Cantilevered Beam

A pair of interdigital electrode (IDE) piezoceramics is used to simultaneously suppress multimode vibrations of a cantilevered beam. This is achieved by connecting the IDE piezoceramics in parallel to a negative capacitive shunt circuit. The governing equations of motion of an IDE piezo/beam system and associated boundary conditions are derived using the Hamilton principle. The obtained mathematical model is validated experimentally Attenuations ranging between 5 and 20 dB are obtained for all the vibration modes over the frequency range of 0-3000 Hz. The presented theoretical and experimental techniques provide invaluable tools for designing simple and effective passive vibration dampers for structures with closely packed modes.

Vibration Control by Using Piezostack Based Mount

2015 ◽  
Vol 738-739 ◽  
pp. 180-183
Author(s):  
Cheng Xun Cui
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Control Method ◽  
Equations Of Motion ◽  
Mass Loading ◽  
Governing Equations ◽  
Specific Mass ◽  
Passive Element ◽  
Feedforward Controller ◽  
Force Characteristics

A vibration control method by using an active hybrid mount featuring piezostack actuators was indicated in this paper. The hybrid mount is composed of piezostack as an active actuator and rubber as a passive element. The hybrid mount was designed and manufactured after experimentally identifying actuating force characteristics of the piezostack and dynamic characteristics of the rubber. Then , a vibration control system with a specific mass loading is constructed, and its governing equations of motion are derived. A feedforward controller is formulated and experimentally realized, in order to actively attenuate vibration transmitted from the base. Finally, vibration control responses are evaluated.

An Investigation of Riser Fairing Instability

2015 ◽  
Author(s):  
Trygve Kristiansen ◽  
Henning Braaten ◽  
Halvor Lie ◽  
Rolf Baarholm ◽  
Kjetil Skaugset
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Diameter Ratio ◽  
Instability Region ◽  
The Other ◽  
Two Degrees Of Freedom ◽  
Linearized Equations ◽  
Different Types ◽  
Instability Regions ◽  
Damping Model

An analysis of galloping of two different types of riser fairings is presented. The first is named “long fairing” (LF) and the other “Short Crab Claw” (Short CC). The first one has a traditionally winged formed shape with a cord-to-diameter ratio of 2.43. The other one is more truncated in shape, and has cord-to-diameter ratio of only 1.4. Results from two related experimental set-ups are included in the work; one 2D experiment with towing tests of fairings that are free to translate and rotate to investigate instability regions, and one 2D experiment with fixed fairings to obtain drag, moment and lift curves. The present analysis is based on two-degrees of freedom, linearized equations of motion, and predicts a range of velocities where instability occurs. Below and above this region, the fairing is stable. Damping complicates the analysis. An empirical damping model is included and discussed. The two fairing types inhibit appreciably different instability characteristics. In particular, the Short CC fairing has a narrower instability region than the long fairing, and is therefore less prone to instabilities.

scholarly journals A Variable Parameter Ambient Vibration Control Method Based on Quasi-Zero Stiffness in Robotic Drilling Systems

Machines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 67
Author(s):  
Laixi Zhang ◽  
Chenming Zhao ◽  
Feng Qian ◽  
Jaspreet Singh Dhupia ◽  
Mingliang Wu
Keyword(s):  
Vibration Control ◽  
Vibration Isolation ◽  
Control Method ◽  
Control Strategies ◽  
Equations Of Motion ◽  
Variable Parameter ◽  
Harmonic Balance Method ◽  
Variable Stiffness ◽  
Ambient Vibration ◽  
Robotic Drilling

Vibrations in the aircraft assembly building will affect the precision of the robotic drilling system. A variable stiffness and damping semiactive vibration control mechanism with quasi-zero stiffness characteristics is developed. The quasi-zero stiffness of the mechanism is realized by the parallel connection of four vertically arranged bearing springs and two symmetrical horizontally arranged negative stiffness elements. Firstly, the quasi-zero stiffness parameters of the mechanism at the static equilibrium position are obtained through analysis. Secondly, the harmonic balance method is used to deal with the differential equations of motion. The effects of every parameter on the displacement transmissibility are analyzed, and the variable parameter control strategies are proposed. Finally, the system responses of the passive and semiactive vibration isolation mechanisms to the segmental variable frequency excitations are compared through virtual prototype experiments. The results show that the frequency range of vibration isolation is widened, and the stability of the vibration control system is effectively improved without resonance through the semiactive vibration control method. It is of innovative significance for ambient vibration control in robotic drilling systems.

Comparative Surface Imaging Study of Multifocal Diffractive Intraocular Lenses

2021 ◽  
Author(s):  
Hyeck Soo Son ◽  
Jung Min Lee ◽  
Ramin Khoramnia ◽  
Chul Young Choi
Keyword(s):  
Imaging Study ◽  
The Other ◽  
Intraocular Lenses ◽  
Optical Surface ◽  
Diffractive Optic ◽  
Atomic Force ◽  
Acceptable Range ◽  
Different Types ◽  
Concentric Pattern

Abstract Purpose To analyse and compare the surface topography and roughness of three different types of diffractive multifocal IOLs. Methods Using scanning electron microscope (SEM, Inspect F, 5.0 KV, maximum magnification up to 20,000) and atomic force microscope (AFM, Park Systems, XE-100, non-contact, area profile comparison, 10 × 10 µm, 40 × 40 µm), the surface quality of the following diffractive IOLs was studied: the AcrySof IQ PanOptix (Alcon, USA), the AT LARA 829MP (Carl Zeiss Meditec, Germany), and Tecnis Symfony (Johnson&Johnson Vision, USA). The measurements were made over three representative areas (central non-diffractive optic, central diffractive optic, and diffractive step) of each IOL. Roughness profile in terms of mean arithmetic roughness (Ra) and root-mean-squared roughness (Rq) values were obtained and compared statistically. Results In SEM examination, all IOLs showed a smooth optical surface without any irregularities at low magnification. At higher magnification, Tecnis Symfony showed unique highly regular, concentric, and lineate structures in the diffractive optic area which could not be seen in the other studied diffractive IOLs. The differences in the measured Ra and Rq values of the Tecnis Symfony were statistically significant compared to the other models (p < 0.05). Conclusion Various different topographical traits were observed in three diffractive multifocal IOLs. The Ra values of all studied IOLs were within an acceptable range. Tecnis Symfony showed statistically significant higher surface Ra values at both central diffractive optic and diffractive step areas. Furthermore, compared to its counterparts, Tecnis Symfony demonstrated highly ordered, concentric pattern in its diffractive surfaces.

RADIATION EXPOSURE TO THE BACK WITH DIFFERENT TYPES OF APRONS

2021 ◽  
Author(s):  
Seung Wan Hong ◽  
Tae Won Kim ◽  
Jae Hun Kim
Keyword(s):  
Radiation Exposure ◽  
Effective Dose ◽  
Exposure Time ◽  
The Other ◽  
Lead Apron ◽  
Type Group ◽  
Air Kerma ◽  
Different Types ◽  
The Relationship

Abstract Physicians and nurses stand with their back towards the C-arm fluoroscope when using the computer, taking things out of closets and preparing drugs for injection or instruments for intervention. This study was conducted to investigate the relationship between the type of lead apron and radiation exposure to the backs of physicians and nurses while using C-arm fluoroscopy. We compared radiation exposure to the back in the three groups: no lead apron (group C), front coverage type (group F) and wrap-around type (group W). The other wrap-around type apron was put on the bed instead of on a patient. We ran C-arm fluoroscopy 40 times for each measurement. We collected the air kerma (AK), exposure time (ET) and effective dose (ED) of the bedside table, upper part and lower part of apron. We measured these variables 30 times for each location. In group F, ED of the upper part was the highest (p &lt; 0.001). ED of the lower part in group C and F was higher than that in group W (p = 0.012). The radiation exposure with a front coverage type apron is higher than that of the wrap-around type and even no apron at the neck or thyroid. For reducing radiation exposure to the back of physician or nurse, the wrap-around type apron is recommended. This type of apron can reduce radiation to the back when the physician turns away from the patient or C-arm fluoroscopy.

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