Modeling and Control of a Deformable Mirror

2002 ◽  
Vol 124 (2) ◽  
pp. 297-302 ◽  
Author(s):  
S. E. Winters ◽  
J. H. Chung ◽  
S. A. Velinsky
Keyword(s):  
Finite Element ◽  
Control System ◽  
Finite Element Model ◽  
Adaptive Optics ◽  
Element Model ◽  
Surface Shape ◽  
System Model ◽  
Deformable Mirror ◽  
Wavefront Aberration ◽  
Control System Model

A multi-input multi-output surface shape control system model is developed to study wavefront aberration correction. The plant model represents a deformable mirror and utilizes a finite element model that is validated using an actual prototype deformable mirror and an interferometer system. The sensor model is based on a Shack-Hartmann sensor, and the controller model is based on a least squares approach. The control system model is used to compare an available Gaussian model with the validated finite element model. Results clearly show the efficacy of the approach and the superiority of the finite element based method. The control approach is expected to be implemented on the adaptive optics system of the National Ignition Facility.

A Structural-Acoustic Vehicle System Model for Noise and Vibration Analysis

2003 ◽  
Author(s):  
Shung H. Sung ◽  
Donald J. Nefske ◽  
Douglas A. Feldmaier ◽  
Spencer J. Doggett
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Exhaust System ◽  
Element Model ◽  
Interior Noise ◽  
System Model ◽  
Structural Vibration ◽  
Vehicle Interior ◽  
Front Suspension ◽  
Vehicle System

A structural-acoustic finite-element model of a sedan-type automotive vehicle is developed and experimentally evaluated for predicting vehicle interior noise and structural vibration. The vehicle system model is developed from finite-element models of the major structural subsystems, which include the trimmed body, front suspension, rear suspension, powertrain and exhaust system. An acoustic finite-element model of the passenger compartment cavity is coupled with the vehicle system model to predict the interior noise response. The predicted interior noise and structural vibration by the vehicle system model are compared with the measured responses for shaker excitation at the axle to 200 Hz. The comparisons demonstrate the accuracy of the structural-acoustic vehicle system model, and they indicate where modeling improvements are required.

scholarly journals Effective finite element model in-loop system of laminated cylindrical structure for multiple inputs and multiple outputs active vibration control

2019 ◽  
Vol 38 (2) ◽  
pp. 664-683 ◽  
Author(s):  
Jinxin Liu ◽  
Minqi Cui ◽  
Baijie Qiao ◽  
Zengguang Li ◽  
Zhibo Yang ◽  
...  
Keyword(s):  
Finite Element ◽  
Control System ◽  
Finite Element Model ◽  
Vibration Control ◽  
Active Vibration Control ◽  
Element Model ◽  
Loop System ◽  
Cylindrical Structure ◽  
Multiple Outputs ◽  
Active Vibration

Active vibration control of large laminated cylindrical structures, for example, the cabin of space, air, surficial or subaqueous vehicles, usually requires multiple inputs and multiple outputs to the system, since there are usually multiple vibration sources and each source contains multiple frequency components. The performance of multiple inputs and multiple outputs control system will be dramatically affected by the complex dynamic behavior of the laminated cylindrical structure, thus an effective model is in great request in analyzing and designing the control system. However, there is seldom distributed parametric model, typically, finite element model, applying to the active vibration control system, because of its computational complexity. In this work, we propose an effective finite element model in-loop system of laminated cylindrical structure for multiple inputs and multiple outputs active vibration control simulation. Firstly, an finite element model of laminated thick cylindrical structure with four-node Mindlin degenerated shell element has been constructed. Then, a model reduction procedure has been proposed to obtain in-loop model of the control system. The numerical global modal analysis and harmonic response analysis of the cylindrical structure have been conducted to verify the correctness of the model. Afterward, a multiple inputs and multiple outputs adaptive algorithm which is able to coup with multiple frequencies and multiple sources vibration has been applied to the finite element model in-loop system. Finally, four numerical case studies have been conducted, in which the vibration sources contain multiple frequency components and artificial colored noises. The result shows that the vibration of the multiple control points can be dramatically suppressed simultaneously, which demonstrates the effectiveness of the algorithm and finite element model in-loop system.

scholarly journals Adaption of Nonstandard Piping Components Into Present Day Seismic Codes

2009 ◽  
Author(s):  
D. T. Clark ◽  
M. J. Russell ◽  
R. E. Spears ◽  
S. R. Jensen
Keyword(s):  
Finite Element ◽  
Linear System ◽  
Finite Element Model ◽  
System Analysis ◽  
Element Model ◽  
System Model ◽  
Rational Approach ◽  
Piping System ◽  
Stress Indices ◽  
Seismic Codes

With spiraling energy demand and flat energy supply, there is a need to extend the life of older nuclear reactors. This sometimes requires that existing systems be evaluated to present day seismic codes. Older reactors built in the 1960s and early 1970s often used fabricated piping components that were code compliant during their initial construction time period, but are outside the standard parameters of present-day piping codes. There are several approaches available to the analyst in evaluating these nonstandard components to modern codes. The simplest approach is to use the flexibility factors and stress indices for similar standard components with the assumption that the nonstandard component’s flexibility factors and stress indices will be very similar. This approach can require significant engineering judgment. A more rational approach available in Section III of the ASME Boiler and Pressure Vessel Code, which is the subject of this paper, involves calculation of flexibility factors using finite element analysis of the nonstandard component. Such analysis allows modeling of geometric and material nonlinearities. Flexibility factors based on these analyses are sensitive to the load magnitudes used in their calculation, load magnitudes that need to be consistent with those produced by the linear system analyses where the flexibility factors are applied. This can lead to iteration, since the magnitude of the loads produced by the linear system analysis depend on the magnitude of the flexibility factors. After the loading applied to the nonstandard component finite element model has been matched to loads produced by the associated linear system model, the component finite element model can then be used to evaluate the performance of the component under the loads with the nonlinear analysis provisions of the Code, should the load levels lead to calculated stresses in excess of Allowable stresses. This paper details the application of component-level finite element modeling to account for geometric and material nonlinear component behavior in a linear elastic piping system model. Note that this technique can be applied to the analysis of ASME B31 piping systems.

Finite Element Simulation of Tire-Rim Interface

1989 ◽  
Vol 17 (4) ◽  
pp. 305-325 ◽  
Author(s):  
N. T. Tseng ◽  
R. G. Pelle ◽  
J. P. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Simulation ◽  
Contact Pressure ◽  
Element Model ◽  
Experimental Measurements ◽  
Inflation Pressure ◽  
Interference Fit ◽  
Element Simulation ◽  
Rubber Composite

Abstract A finite element model was developed to simulate the tire-rim interface. Elastomers were modeled by nonlinear incompressible elements, whereas plies were simulated by cord-rubber composite elements. Gap elements were used to simulate the opening between tire and rim at zero inflation pressure. This opening closed when the inflation pressure was increased gradually. The predicted distribution of contact pressure at the tire-rim interface agreed very well with the available experimental measurements. Several variations of the tire-rim interference fit were analyzed.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

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