Mechanisms of Localized Vibration Control in Complex Structures

1996 ◽  
Vol 118 (1) ◽  
pp. 135-139 ◽  
Author(s):  
J. Hannsen Su ◽  
C. E. Ruckman
Keyword(s):  
Vibration Control ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Control Strategies ◽  
Complex Structure ◽  
Element Model ◽  
Property A ◽  
Box Girders ◽  
Six Degrees Of Freedom ◽  
Realistic Structure

This paper describes a numerical study of mechanisms for controlling all six degrees of freedom in localized areas of a complex structure. In localized vibration control, the controller attempts to stabilize one or more localized areas on the structure rather than attempting to stabilize the entire structure. The relative performance levels of different control strategies are evaluated by examining a frequency-dependent disturbance rejection property. A flat plate supported by two box girders is used as an example realistic structure. Plant dynamics from a finite-element model are used to draw general conclusions regarding the mechanisms by which localized vibration control is exerted.

Structural Analysis of Riveted Structures Using a New FE Modelling Technique

2010 ◽  
Author(s):  
Michele Ferracci ◽  
Francesco Vivio ◽  
Vincenzo Vullo
Keyword(s):  
Degrees Of Freedom ◽  
Complex Structure ◽  
Element Model ◽  
3D Models ◽  
Fatigue Behaviour ◽  
Fe Analysis ◽  
Structural Behaviour ◽  
Fe Modelling ◽  
Closed Form Solutions ◽  
Riveted Joints

A theoretical approach, in order to define the structural behaviour of riveted joints, is presented. The closed form solutions lead to the definition of a Rivet Element useful to FE models of multi-riveted structures. The objective is an accurate evaluation of the local stiffness of riveted joints in FE analysis, which is fundamental to perform a reliable simulation of multi-joint structures and, consequently, a good estimate of loads acting on connections; this makes it possible to introduce new general criteria allowing, for example, to predict fatigue behaviour. On the other hand, a low number of degrees of freedom is needed when several connections are present in a complex structure. The goal is to reach a reliable model of the rivet region which can be used as the basis to develop a Rivet Element in FE analysis. The proposed Rivet Element combines the precision in the simulation with a very limited number degrees of freedom in the finite element model of a complex structure having several rivets. In the present paper the structural behavior of two simple riveted specimens is investigated experimentally and numerically using a new Rivet Element. A comparison with a joint model performed with very refined non-linear 3D models of rivet and with experimental data is performed and a good agreement is shown.

Multiscale Control to Meet the Conflicting Nanoscale Performance Requirements

2005 ◽  
Author(s):  
Huzefa Shakir ◽  
Won-Jong Kim
Keyword(s):  
Degrees Of Freedom ◽  
Reference Model ◽  
Control Strategies ◽  
Mass Model ◽  
Integral Term ◽  
Six Degrees Of Freedom ◽  
Performance Requirements ◽  
Model Following ◽  
Control Schemes ◽  
Domain Performance

In this paper, we consider the problem of designing a multiscale control for plants with conflicting time-domain performance requirements. These results follow from the conventional optimal proportional-integral (PI) control. Four different design methods are proposed: (1) a controller-switch technique which makes use of employing two different controllers designed to meet two different performances and are switched during the course of operation, (2) an integral-reset scheme, which resets the integral term in the control law when the new reference point is reached, (3) controller-switch and integral-reset schemes put together to take benefits of both of them, (4) a model-following approach that uses a dynamic reference model without increasing the overall dimension of the system. The objective of the last scheme is to make the output of the plant track the output of the model as closely as possible. Stability analyses and a comparison between the performances of these methods are given. All these methods give better performances as compared with conventional control schemes. Block diagrams are given and step responses are obtained to demonstrate the proposed methods. A six degrees-of-freedom (DOFs) magnetically levitated (maglev) stage with a second-order pure-mass model has been used to demonstrate the capabilities of the aforementioned control strategies. These strategies are not plant-specific and may be generalized to any higher-order plant.

scholarly journals INVESTIGATION OF LOCAL AND MODAL BASED ACTIVE VIBRATION CONTROL STRATEGIES ON THE EXAMPLE OF AN ELASTIC SYSTEM

2019 ◽  
Vol 19 (2) ◽  
pp. 32-45 ◽  
Author(s):  
Christoph PEUKERT ◽  
Patrick PÖHLMANN ◽  
Marcel MERX ◽  
Steffen IHLENFELDT ◽  
Jens MÜLLER
Keyword(s):  
Vibration Control ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Elastic System ◽  
Control Strategies ◽  
Active Vibration Control ◽  
Modal Control ◽  
Control Approach ◽  
Control Loops ◽  
The Impact

Nowadays, feed axes are often equipped with multiple parallel-acting actuators in order to increase the dynamics of the machine tool. Also, additional actuators for active damping are widely used. Normally, the drives or actuators are controlled independently without consideration for the impact on each other. In contrast, by using the modal space control, the system can be decoupled and the modal control loops can be adjusted independently. This control approach is particularly suitable for motion systems, such as machine tools, which have more drives or actuators than degrees of freedom of movement. This paper deals with the pre-investigation of the modal-based vibration control for machine tools with additional actuators. The object of investigation is an elastic system with a movable saddle. The modal-based control is compared with a local control approach. The results obtained experimentally on the test rig are presented. The modal control is superior since, with the modal approach, each control loop corresponds to a specific vibration mode, and the control law for this loop is designed to provide the desired performance of the control system at the corresponding resonance frequency. The parameterisation of the control loops is simplified by modal control, since the modes can be controlled independently.

A Numerical Study on Motion Responses of a Mat-Support Jack-Up During Positioning

2015 ◽  
Author(s):  
Zhaode Zhang ◽  
Yuhong Wang
Keyword(s):  
Numerical Analysis ◽  
Environmental Conditions ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Analysis Software ◽  
Floating Structure ◽  
Six Degrees Of Freedom ◽  
Motion Responses ◽  
Different Depths ◽  
Jack Up

The motion response of a mat-support jack-up during positioning is studied in this paper using numerical analysis software SESAM. In the process of jack-up positioning, the square bottom mat is gradually lowered and the floating jack-up, secured by anchor chains, moves in six degrees of freedom in response to the dynamic loading of wave, current and wind combined. Numerical simulations are carried out to solve motion responses of the floating structure with mat at different depths. The sensitivity of motion responses to wave periods and directions are analyzed. The maximum motion amplitudes under the design environmental conditions and the risk of the mat crashing with the seafloor are evaluated.

Experimental and Numerical Study of the Motions of a Turret Moored FPSO in Waves

2004 ◽  
Vol 127 (3) ◽  
pp. 197-204 ◽  
Author(s):  
C. Guedes Soares ◽  
N. Fonseca ◽  
R. Pascoal
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Numerical Data ◽  
Irregular Waves ◽  
Experimental Program ◽  
Six Degrees Of Freedom ◽  
Strip Theory ◽  
Wide Range ◽  
Wave Heights ◽  
Mooring Forces

This paper presents the results of an experimental program carried out with a model of a FPSO (Floating Production, Storage and Offloading) unit moored and subjected to incoming waves. In regular waves, a wide range of wavelengths were tested and the effect of the wave amplitude was also investigated. In irregular waves the model was subjected to different sea states, including very severe significant wave heights. The measured responses include the six degrees of freedom absolute motions, relative motions, and the mooring forces. The experimental data of surge, heave, and pitch is compared with calculated results from a Green’s function panel method and a strip theory program. In general, the agreement between experimental and numerical data is very good.

Experimental and numerical study of friction and .giffness characteristics of small rolling tires

2011 ◽  
Vol 39 (1) ◽  
pp. 5-19 ◽  
Author(s):  
R. van der Steen ◽  
I. Lopez ◽  
H. Nijmeijer
Keyword(s):  
Steady State ◽  
Numerical Study ◽  
Complex Structure ◽  
Element Model ◽  
Steady State Solution ◽  
Experimental Results ◽  
Small Scale ◽  
The Road ◽  
Rubber Compounds ◽  
Complex Measurement

Abstract Virtual testing is nowadays the standard in the design process of new tires. Besides modeling the static response of the tire itself, the dynamics of a rolling tire in contact with the road needs to be incorporated. Due to the uncontrollable environmental conditions and the complex structure of the tires, it is advantageous to use small-scale testing under more controlled conditions. Experimental characterization of frictional properties of rubber compounds is, however, limited due to the necessity of complex measurement systems. In this paper a commercially available laboratory abrasion and skid tester is used to ide.gify both friction and .giffness characteristics of the same rubber compound. The obtained friction properties are implemented in a finite element model of the setup, and different validation steps are presented. Finally, a steady-state transport approach is used to efficiently compute a steady-state solution, which is compared with the experimental results. The numerical results show a good qualitative agreement with the experimental results.

Computerized Three-Dimensional Finite Element Reconstruction of the Left Ventricle from Cross-Sectional Echocardiograms

1984 ◽  
Vol 6 (1) ◽  
pp. 48-59 ◽  
Author(s):  
P. E. Nikravesh ◽  
D. J. Skorton ◽  
K. B. Chandran ◽  
Y. M. Attarwala ◽  
N. Pandian ◽  
...  
Keyword(s):  
Finite Element ◽  
Left Ventricle ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Element Model ◽  
Left Ventricular Geometry ◽  
Six Degrees Of Freedom ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

A computerized method for the generation of a three-dimensional finite element mesh of left ventricular geometry is presented. The technique employs two dimensional echocardiographic images of the left ventricle. The echocardiographic transducer is attached to an articulated, computerassisted, position registration arm with six degrees-of-freedom. These six degrees-of-freedom record the location and orientation of the transducer, when images are obtained, referenced to an external point. Eence, the images are digitized and aligned relative to one another, then several interpolation and curve fitting steps are used to reconstruct a threedimensional finite element model of the left ventricle. The finite element model can be used for volume determination, stress analysis, material property identification, and other applications.

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