Passive Isolation by Nonlinear Boundaries for Flexible Structures

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Xiao-Ye Mao ◽  
Hu Ding ◽  
Li-Qun Chen
Keyword(s):  
Vibration Isolation ◽  
Flexible Structures ◽  
Linear Structure ◽  
Response Prediction ◽  
Structural Vibration ◽  
Original Structure ◽  
Analytic Method ◽  
Stress Control ◽  
Passive Isolation ◽  
Passive Technique

A simple passive technique of vibration isolation for flexible structures by nonlinear boundaries is investigated, which to our best knowledge is the first study of its kind reported in the literature. The equations of the structure are derived with Hamilton’s principle. An iterative analytic method is investigated to improve the accuracy of the response prediction. The effect of nonlinear boundaries of the structure is studied compared with the linear structure. It is found that stronger nonlinearities in the boundary make the system more stable. Analytical and simulation results show that nonlinear boundaries can significantly reduce the vibration and stress of flexible structures. It is important to point out that with the help of nonlinear boundaries, structural vibration and stress control can be achieved without altering the original structure.

Structural Vibration Control for Bridge Towers and its Effect Under Wind Excitation Using a Wind Tunnel

1997 ◽  
Author(s):  
Fumio Doi ◽  
Kazuto Seto ◽  
Mingzhang Ren ◽  
Yuzi Gatate
Keyword(s):  
Wind Tunnel ◽  
Vibration Control ◽  
Active Vibration Control ◽  
Flexible Structures ◽  
Structural Vibration ◽  
Magnetic Actuators ◽  
Displacement Sensors ◽  
Active Vibration ◽  
Electro Magnetic ◽  
Tower Model

Abstract In this paper we present an experimental investigation of active vibration control of a scaled bridge tower model under artificial wind excitation. The control scheme is designed on the basis of a reduced order model of the flexible structures using the LQ control theory, with a collocation of four laser displacement sensors and two hybrid electro-magnetic actuators. The experimental results in the wind tunnel show that both the bending and the twisting vibrations covering the first five modes of the structure are controlled well.

scholarly journals Research on dynamic characteristics of plate under pedestrian excitation based on Newmark-β

2018 ◽  
Vol 37 (4) ◽  
pp. 682-699
Author(s):  
Xinfang Ge ◽  
Weirong Wang ◽  
Wei Yuan
Keyword(s):  
Rectangular Plate ◽  
Dynamic Characteristics ◽  
Vibration Isolation ◽  
Great Influence ◽  
Interaction Model ◽  
Vertical Direction ◽  
Structural Vibration ◽  
Normal Walking ◽  
Plate Structure ◽  
Pedestrian Excitation

Development of micro and ultra-precision machining, precision instruments and equipment, precision assembly and testing has put forward more and more high requirements to vibration isolation on environmental elements, especially the pedestrian excitation generated by workers' normal walking. Therefore, it is very important to study the pedestrian excitation's influence on vibration characteristics of precision instruments and equipment. In this study, dynamic model including mathematical model of pedestrian excitation, interaction model between pedestrian and rectangular plate structure, the human–plate coupled dynamic equation in vertical direction of pedestrian–plate structure was established. And then we use the Newmark-β method to solve the time-domain step-by-step integration of the first four order modes' dynamic equations and study the influence of the linear notion trajectory along the central axis direction on the dynamic characteristics of the rectangular plate. By simulation, we discussed plate structure response under different conditions, including plate structure displacement and acceleration response under the single person excitation with different velocities, under normal walking velocity with different number of pedestrians and under this case of different distance between two pedestrians. The results show that the structural vibration induced by pedestrian excitation has great influence on dynamic characteristics of plate.

Hybrid Control of Rotating Beams Using Pattern Search Based Optimization Technique

2018 ◽  
Author(s):  
Rajiv Kumar Vashisht ◽  
Qingjin Peng
Keyword(s):  
Smart Materials ◽  
Optimization Technique ◽  
Flexible Structures ◽  
Pattern Search ◽  
Feedback Controller ◽  
Structural Vibration ◽  
Flexible Beam ◽  
Constrained Layer Damping ◽  
Rotating Beams ◽  
Passive Constrained Layer Damping

Rotating beams are quite common in rotating machinery e.g. fans of compressors in an airplane. This paper presents the experimental, hybrid, structural vibration control of flexible structures to enhance the vibration behavior of rotating beams. Smart materials have been used as sensors as well as actuators. Passive constrained layer damping (PCLD) treatment is combined with stressed layer damping technique to enhance the damping characteristics of the flexible beam. To further enhance the damping parameters, a closed form robust feedback controller is applied to reduce the broadband structural vibrations of the rotating beam. The feed forward controller is designed by combing with the feedback controller using a pattern search based optimization technique. The hybrid controller enhances the performance of the closed loop system. Experiments have been conducted to validate the effectiveness of the presented technique.

scholarly journals Bionic Drag Reduction for Box Girders Based on Ostracion cubicus

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4392
Author(s):  
Yupu Wang ◽  
Wenming Cheng ◽  
Run Du ◽  
Shubiao Wang
Keyword(s):  
Drag Reduction ◽  
Large Scale ◽  
Flexible Structures ◽  
Development Trend ◽  
Windward Side ◽  
Original Structure ◽  
Box Girders ◽  
Aerodynamic Parameter ◽  
Box Girder ◽  
Rectangular Cylinder

With the development trend of large-scale and flexible structures in engineering, the research on drag reduction of structures becomes more urgent. This paper presents a drag reduction design method for box girders based on the bionic method. Through the analysis of the Ostracion cubicus body shape, three features of the “fish mouth”, which were helpful for drag reduction were extracted. Then the bionic design model with the height of the box girder (D) as the design variable was obtained. By attaching lightweight materials to the windward side, the bionic shape of the structure can be realized without changing the loading characteristics of the original structure. Taking a box girder (rectangular cylinder, side ratio B/D = 0.6) as a prototype, the flow around two structures (rectangular cylinder and bionic attachment cylinder) was numerically simulated. The results show that the drag coefficient of the bionic attachment structure is reduced by 66.5%. The reduction of wind-load means that this method can save energy consumption of the equipment. Meanwhile, the aerodynamic parameter oscillation of the structure is weakened, which represents that the bionic attachment structure can effectively reduce the wind-induced vibration on the structure and improve the stability of the structure in the wind field.

Case history building structural vibration isolation for 500 Atlantic Avenue

2006 ◽  
Vol 120 (5) ◽  
pp. 3207-3207
Author(s):  
Gregory Tocci ◽  
George Wilson ◽  
James Phillips ◽  
Gladys Unger ◽  
James Moore
Keyword(s):  
Case History ◽  
Vibration Isolation ◽  
Structural Vibration

Closed-Loop Input Shaping for Flexible Structures Using Time-Delay Control1

1999 ◽  
Vol 122 (3) ◽  
pp. 454-460 ◽  
Author(s):  
Vikram Kapila ◽  
Anthony Tzes ◽  
Qiguo Yan
Keyword(s):  
Time Delay ◽  
Closed Loop ◽  
Flexible Structures ◽  
System Stability ◽  
Structural Vibration ◽  
Delay Systems ◽  
Linear Matrix ◽  
Input Shaping ◽  
Closed Loop Control ◽  
Loop Control

Input shaping techniques reduce the residual vibration in flexible structures by convolving the command input with a sequence of impulses. The exact cancellation of the residual structural vibration via input shaping is dependent on the amplitudes and instances of impulse application. A majority of the current input shaping schemes are inherently open-loop where impulse application at inaccurate instances can lead to system performance degradation. In this paper, we develop a closed-loop control design framework for input shaped systems. This framework is based on the realization that the dynamics of input shaped systems give rise to time delays in the input. Thus, we exploit the feedback control theory of time delay systems for the closed-loop control of input shaped flexible structures. A Riccati equation-based and a linear matrix inequality-based frameworks are developed for the stabilization of systems with uncertain, multiple input delays. Next, the aforementioned framework is applied to two input shaped flexible structure systems. This framework guarantees closed-loop system stability and performance when the impulse train is applied at inaccurate instances. Two illustrative numerical examples demonstrate the efficacy of the proposed closed-loop input shaping controller. [S0022-0434(00)00103-9]

Force Feedback in Adaptive Trusses for Vibration Isolation in Flexible Structures

1997 ◽  
Vol 119 (3) ◽  
pp. 365-371 ◽  
Author(s):  
W. W. Clark ◽  
H. H. Robertshaw
Keyword(s):  
Vibration Isolation ◽  
Force Feedback ◽  
Flexible Structures ◽  
Control Law ◽  
Control Problems ◽  
Sensors And Actuators ◽  
Dynamic Forces ◽  
Active Vibration ◽  
The Ideal

This paper addresses the transmission of unwanted vibrations in flexible structures by actively minimizing dynamic forces seen at critical locations within the structure. An adaptive truss serves as an active interface between the two isolated sides of the structure, and force-feedback within individual links of the truss is the governing control law. The use of an adaptive truss allows the problem to be viewed as a set of localized control problems with collocated sensors and actuators. This paper first discusses the ideal capabilities of force feedback for active vibration isolation, and then presents the analytical and experimental results of a case study which shows significant reduction in transmitted vibrations.

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