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Semi-active control strategies for buildings subject to near-field earthquakes

Proceedings of SPIE - The International Society for Optical Engineering 2000年 3988卷 359-370页

作者： Agrawal, A.K. Yang, J.N. City Coll of New York New York United States

The near-field earthquake ground motion is characterized by high peak accelerations and velocity pulses with long period components as well as large ground displacements. Such characteristics are responsible for severe damages to flexible structures. The peak ground acceleration occurs in the form of a shock, rather than a gradual build-up. As a result, passive dampers may not dissipate energies quick enough to prevent a serious damage to structures. Recently, a resetting or switching semi-active stiffness damper (RSASD or SSASD) and a semi-active electromagnetic friction damper (SAEMFD) have been shown to be effective in reducing the structural response due to dynamic loads. In this paper, the performance and effectiveness of these two semi-active hybrid isolation systems are studied extensively for base-isolated buildings subject to near-field earthquakes. Numerical results clearly demonstrate that these two semi-active dampers are effective in protecting the integrity of base-isolated structures during near-field earthquakes.

关键词： Structural analysis

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Adaptive fuzzy control for a structure-MR damper system

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Proceedings of SPIE - The International Society for Optical Engineering 2000年 3988卷 105-115页

作者： Zhou, Li Chang, Chih-Chen Hong Kong Univ of Science & Technology Kowloon Hong Kong

Because of the intrinsically nonlinear nature of semiactive control devices, development of control strategies that are practically implementable and can fully utilize the capabilities of these promising devices is an important and challenging task. In this study, we propose the use of an adaptive fuzzy strategy for the control of a structure installed with a magnetorheological (MR) damper. The proposed adaptive fuzzy control strategy involves the design of a fuzzy controller and an adaptation law for the combined structure-MR damper system. The objective control is to minimize the difference between a desirable response and the response of the combined system by intelligently adjusting its active component, the MR damper. The use of the adaptation law requires on-line monitoring of system response but eliminates the needs of acquiring any characteristics of the combined system in advance. The combination of the fuzzy controller and the adaptation law provides a robust control strategy that can be used on a nonlinear or uncertain system under random loads. A numerical example which involves controlling a single-degree-of-freedom structure under earthquake excitation using a MR damper is studied and presented. The simulated results indicate that the proposed adaptive fuzzy control strategy is quite effective and appropriate for the use of semiactive devices such as the MR damper.

关键词： Intelligent structures

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Design of robust controllers for smart structural systems with structured uncertainties

Design of robust controllers for smart structural systems wi...

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smart structures and materials 2000 - mathematics and control in smart structures

作者： Sana, Sridhar Rao, Vittal S. Univ of Missouri-Rolla Rolla MO United States

A controller synthesis procedure based on Popov stability results for reducing the conservatism in the design is introduced. This design procedure is applied on a smart structural test article and the results are pres... 详细信息

关键词： Intelligent structures

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Designing for piezoelectric ceramic wafers bonded on structures using force transfer criteria

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smart materials & structures 2000年第2期9卷 157-162页

作者： Wang, XM Ye, L Mai, YW Galea, SC Univ Sydney Dept Mech & Mechatron Engn Ctr Adv Mat Technol Ctr Expertise Damage Mech Sydney NSW 2006 Australia DSTO Aeronaut & Maritime Res Lab Airframes & Engines Div Melbourne Vic 3001 Australia

Piezoelectric ceramic wafers embedded or surface mounted are able to generate transverse forces to control structural shape and vibration. These actuators are excited by applying an electric field through the thickness of the piezoelectric ceramic wafer. The proper design of their dimensions such as wafer thickness, and applied actuation voltage will enhance the system reliability, and guarantee the optimal control authority. This paper shows that the force transfer from the piezoelectric ceramic wafer to the structure, rather than the shear stress transfer in bond lines, becomes a key issue in the design when the length relative to the thickness of the piezoelectric ceramic wafer is large. It should be noted at this point that the shear stress distribution in the bond lines may influence the durability of the piezoelectric ceramic actuation system and, therefore, should also be considered when designing the system as a whole. This aspect of design is not discussed here. The force transfer is basically determined by the force transfer efficiency and block force in association with the wafer thickness. Therefore, this paper presents a design window for piezoelectric ceramic wafers bonded onto structures that is based on the relations between the force transfer and the wafer thickness, and also accounting for the applied actuation voltage and dielectric breakdown voltage of the piezoelectric material. The design window clearly describes the upper bound of the force transfer and the maximum value that can be achieved. It is also used to find an appropriate wafer thickness and actuation voltage when a minimum value of force transfer is required. In addition, an analytical model is developed in order to express the relation between the force transfer and the wafer thickness. This model is compared to the results from finite-element analysis. Limitations of the analytical model are described.

关键词： Intelligent materials

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Brillouin-active fibers for optical sensing, logic and computation in smart structures

Brillouin-active fibers for optical sensing, logic and compu...

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smart structures and materials 2000 Conference

作者： Yu, C Kim, YK Foreman, J N Carolina Agr & Technol State Univ Greensboro NC 27411 USA

ISBN: (纸本)0819436046

We have studied stimulated Brillouin scattering in single-mode optical fibers as a sensor for both temperature and strain. Shape Memory alloy Nitinol is also studied for enhancement of active sensing and control in structures. We have introduced the hybrid sBs amplifier/oscillator scheme, in which the short fiber amplifier performs sensing and the long oscillator fiber provides the required signal. The sensing fiber can be coated with SMA thin film for ruggedness, increased sBs sensitivity to temperature and strain, and memory or trainability. The oscillator/amplifier scheme also serves as a building block in the design of optical threshold logic circuits, optical computation, and more sophisticated sensing schemes. Such sensing schemes can be highly competitive with those based on fiber Bragg grating. The incorporation of SMA thin films provides memory capability to all these applications.

关键词： Optical fibers Oscillators Shape memory alloys Sensors Optical amplifiers Fiber amplifiers Logic Neural networks smart structures Scattering

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Numerical analysis of fracture in smart composite structures

Numerical analysis of fracture in smart composite structures

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6th International Conference on Damage and Fracture Mechanics

作者： Kuna, M Freiberg Univ Min & Techol Inst Mech & Machine Components Freiberg Germany

ISBN: (纸本)1853128120

Modern adaptive mechanical systems consists of composite structures with integrated sensors and actuators made of smart materials, as e.g. piezoelectric ceramics. For the development and application of such, smart composite structures, problems of fracture and fatigue play an essential role. In the paper, the concepts of piezoelectric fracture mechanics are applied to crack-like defects in smart composite structures subjected to electrical and mechanical loads. Effective finite element techniques are suggested for computing the singular coupled electromechanical fields at the crack tips and for determining the fracture controlling parameters like mechanical as well as electrical stress intensity factors and energy release rates. Their potential use for fracture analysis in adaptive structures is demonstrated by treating various problems of cracks and interface cracks in a composite laminate with embedded piezoelectric ceramic layers.

关键词： Composite structures

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Uncertainty models for control of distributed actuator and sensor arrays

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Proceedings of SPIE - The International Society for Optical Engineering 2000年 3984卷 415-424页

作者： Gorinevsky, Dimitry Stein, Gunter Honeywell Technology Cent Cupertino United States

This paper considers control analysis approaches for systems incorporating large actuator and sensor arrays. Applications of such systems are increasingly common because of the development of micro-systems technology. Many imaging systems have large one-dimensional or two-dimensional arrays of actuators. This includes RF or optical reflectors, display, printing, and other systems. Signal processing for large sensor arrays has well-established theory and applications, especially in imaging. At the same time, approaches to control of large distributed actuator and sensor arrays are much less developed. This paper considers one of the fundamental issues and design and analysis of large actuator and sensor array systems. The key notion in modern feedback control theory is the notion of uncertainty and associated notion of control robustness to this uncertainty. In control of dynamical systems evolving in time, structured uncertainty models are commonly accepted for theoretical analysis (Structured Singular Value or μ-analysis) and practical control design. In control of spatially distributed processes, there is a need to establish appropriate models of the uncertainty of the system spatial and dynamical characteristics. This paper discusses an extension of structured uncertainty models towards controlled systems with spatially distributed arrays of actuators and sensors. Unlike a dynamical uncertainty, spatial uncertainty is not causal in the spatial coordinate. This leads to related but different uncertainty models in the two case. For spatial coordinates, boundary effects also contribute to the modeling error. By using the discussed uncertainty models, the existing methods of robust control design and analysis can be extended towards spatially distributed systems. As an illustrative example, this paper demonstrates an application of the developed approach to a one-dimensional model of a flexible reflector with a distributed actuator array for shape control.

关键词： Uncertain systems

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Integrated structures/controls optimization of a smart composite plate with segmented active constrained layer damping

Integrated structures/controls optimization of a smart compo...

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smart structures and materials 2000 Conference

作者： Beri, R Chattopadhyay, A Nam, C Arizona State Univ Dept Mech & Aerosp Engn Tempe AZ 85287 USA

ISBN: (纸本)0819436038

A rigorous multi-objective optimization procedure, is developed to address the integrated structures/control design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatment. The Kresselmeier-Steinhauser function approach is used to formulate this multidisciplinary problem. The goal is to control vibration without incorporating a weight penalty. Objective functions and constraints include damping ratios, structural weight and natural frequencies. Design variables include the ply stacking sequence, dimensions and placement of segmented ACL. The optimal designs show improved plate vibratory characteristics and reduced structural. weight. The results of the multi-objective optimization problem are compared to those of a single objective optimization with vibration control as the objective. Results establish the necessity for developing the integrated structures/controls optimization procedure.

关键词： integrated design optimization smart composites segmented active constrained layer hybrid displacement field

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Model reduction for active vibration control

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Proceedings of SPIE - The International Society for Optical Engineering 2000年 3985卷 780-789页

作者： Henriot, Philippe Verge, Michel Coffignal, Gerard ENSAM Paris Paris France

In active vibration control, the modeling of the mechanical structure is generally done using the finite element method. The model obtained must be reduced to compute the controller. Model reduction must achieve two objectives: the reduced model must keep its initial dynamic behavior in the frequency range of interest; and the influence of neglected dynamics must be minimized to limit the risk of spillover. In this paper, we propose an original criterion for the selection of the controlled dynamics. This criterion has the great advantage to be independent of the placement of actuators and sensors. First, the structure is successively reduced to only one mode. For each one, it is obvious to find the optimal location of one actuator and one sensor. Thus, we obtain as many SISO systems of second order as the number of modes. Then, the Hinfinity norms of these systems are computed and the modes are sorted regarding to their influence in the global response of the system. To show the efficiency of the method, it is applied to an experimental structure: an LQR controller is designed and several tests are performed. A comparison is also done with other classical techniques of reduction.

关键词： Vibration control

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Sensor/actuator optimal design for active vibration control of shell structure

Sensor/actuator optimal design for active vibration control ...

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smart structures and materials 2000 Conference

作者： Kim, SJ Hwang, JS Mok, J Seoul Natl Univ Dept Aerosp Engn Seoul 151742 South Korea

ISBN: (纸本)0819436038

In this paper, a distributed sensor and actuator are designed for the active vibration control of shell structure. To prevent the adverse effect of spillover, distributed modal sensor/actuator system is established by optimizing the electrode pattern and the lamination angle (if poly vinylidene fluoride (PVDF). Finite element programs are developed to consider the curved structures integrated with PVDF sensor and actuator. The nine-node Mindlin shell element is used for finite element discretization. The electrode pattern and the lamination angle of PVDF sensor/actuator are optimized using genetic algorithm. The sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. For the verification of the design, numerical simulation and real-time vibration control experiment of the integrated smart structure are performed using discrete LQG method as the control law. A singly curved cantilevered smart shell structure integrated with distributed modal sensor/actuator for the suppression of the first and second modes is manufactured for the experiment. The vibration suppressions of control modes are successfully achieved as expected.

关键词： Sensors Ferroelectric polymers Actuators Electrodes Active vibration control Transducers Binary data control systems Genetic algorithms Distributed computing

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