This paper is concerned with the basic mathematical aspects of a newly suggested theory of smart composite structures. The governing equations describing the behavior of a smart composite structure incorporating senso...
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ISBN:
(纸本)0819420905
This paper is concerned with the basic mathematical aspects of a newly suggested theory of smart composite structures. The governing equations describing the behavior of a smart composite structure incorporating sensors and actuators are derived. The basic optimization problems in the theory of smartstructures are formulated. The discussion on some relevant aspects of the optimal control theory, and on similarities and discrepancies between the theory of smartstructures and theory of optimal control is provided. The basic optimization problems for the smartstructures are illustrated by the applied examples of practical interest. In these examples, two major sources of control are emphasized, namely, residual strains and material properties.
Piezoceramic actuators are used in tandem with conventional actuator to design control laws for a Timoshenko slewing beam. The equations are presented in an abstract first order form. Feedback laws are obtained in the...
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ISBN:
(纸本)0819420905
Piezoceramic actuators are used in tandem with conventional actuator to design control laws for a Timoshenko slewing beam. The equations are presented in an abstract first order form. Feedback laws are obtained in the context of LQR theory. Convergent functional gains are obtained and time responses of the closed loop system are presented. It is shown that the piezoceramic actuators can significantly enhance the closed-loop response of the system.
In this paper we are concerned with smartmaterials that contain many actuators and sensors along with digital signal processing electronics that allow for the implementation of a control algorithm. smartmaterials ha...
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ISBN:
(纸本)0819420905
In this paper we are concerned with smartmaterials that contain many actuators and sensors along with digital signal processing electronics that allow for the implementation of a control algorithm. smartmaterials have been proposed for the active control of sound from a vibrating structure. Here we investigate the design of structural control systems for these smartstructures for noise suppression. First we model the radiated acoustic waves in terms of the velocity of the surface of the structure. Then we formulate an optimal control problem as a linear system that has a transmission zero in the path between the disturbance force and the shape that radiates best. A geometric description of the problem relates control problem to the acoustics. This optimal control problem is solved using a genetic algorithm.
Thanks to the recent advances in control of structures by distributed piezoelectric elements, the concept of independent control and sensing of the structural modes has reemerged in the published literature. In partic...
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ISBN:
(纸本)0819420905
Thanks to the recent advances in control of structures by distributed piezoelectric elements, the concept of independent control and sensing of the structural modes has reemerged in the published literature. In particular, to this end, piezoelectric orthogonal actuators and sensors have been introduced. On the other hand, Independent Modal-Space control (IMSC) of distributed-parameter-system (DPS) is a well-known approach advocated by the author and his associates throughout the past two decades. In the 1980's it has been shown by its proponents that the IMSC method ultimately represents a globally optimal distributed-control and distributed-sensing approach to structural control. Piezoelectric elements are not exception to the general theoretical concepts of distributed-control and sensing of DPS's via the IMSC method. By a constructive theoretical approach, it is shown in this paper that the recent results characterized by the phrases `independent modal control' and `orthogonal actuators and sensors' constitute precise piezoelectric realizations of the IMSC method of the author and his past associates, almost two decades after its introduction.
The problem of controlling the bending vibration of cantilevers modeled as thin-walled beams of closed cross-section incorporating a number of nonclassical effects, such as transverse shear, secondary warping and hete...
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ISBN:
(纸本)0819420905
The problem of controlling the bending vibration of cantilevers modeled as thin-walled beams of closed cross-section incorporating a number of nonclassical effects, such as transverse shear, secondary warping and heterogeneity, is investigated. The control is carried out by means of piezoelectric materials bonded or embedded into the host structure. The control law represents a combination of displacement, velocity and acceleration feedback. The capabilities and efficiency of this control methodology are illustrated and a number of relevant conclusions are outlined.
The proceedings contains 164 papers. Following topics are discussed: biological materials;intelligent composites and health monitoring;smart composites and optical fibers;smart sensors and systems;electro- and magneto...
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ISBN:
(纸本)0819421650
The proceedings contains 164 papers. Following topics are discussed: biological materials;intelligent composites and health monitoring;smart composites and optical fibers;smart sensors and systems;electro- and magnetorheologic fluids;polymers and polymeric gels for smart systems;shape memory alloys and adaptive materials;smart systems using piezoelectric sensors and applications;vibration and sound control;intelligent processing;mathematics for smartmaterials and structures;and smart technology applications.
This paper describes an approach for designing a structure-control system based on the linear quadratic regulator which suppresses vibrations in structures. Bounds are placed on the control forces to simulate real act...
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ISBN:
(纸本)0819420905
This paper describes an approach for designing a structure-control system based on the linear quadratic regulator which suppresses vibrations in structures. Bounds are placed on the control forces to simulate real actuators. The structure and control system are optimized with an objective function of the total weight of the structure and the control devices. The design variables are the bounds (which are proportional to the weight of the control devices) on each control force and the cross-sectional areas of the structural elements. A constraints are placed on the time required to reduce the energy of the vibration to 5% of its initial value, structural frequencies and upper and lower bounds on the design variables. As an example to illustrate the application of an approach, a wing box idealized by rod elements is used. The actuators and sensors are collocated and assumed to be embedded in structural elements.
A finite element (FE) formulation is presented for modeling the dynamical response of smartstructures with embedded piezoelectric ceramic devices subjected to transient loading. The FEM formulation presented is based...
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ISBN:
(纸本)0819420905
A finite element (FE) formulation is presented for modeling the dynamical response of smartstructures with embedded piezoelectric ceramic devices subjected to transient loading. The FEM formulation presented is based on a variational principle using the concept of virtual work. An unconditionally stable method (α-method) is utilized for the direct integration of the equations of motion and can be put in the form of a 3-step linear multistep method of second order equations. A thin cantilever plate with piezoelectric devices is investigated to show the feasibility of the analysis and numerical simulation. The code employs 20 node isoparametric 3D piezoelectric elements, flat-shell elements and transition elements at the interface of the piezoelectric devices and the plate. Under a given external loading, the structure and the embedded sensors deform and the voltage response of the sensor can be calculated as a function of time. Such calculations can be useful as a design tool for smartstructures.
A finite element approach has been used to model phase transitions in electro-mechanically coupled material. The approach is applicable to modeling a broad range of material behavior, including repolarizations in ferr...
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ISBN:
(纸本)0819420905
A finite element approach has been used to model phase transitions in electro-mechanically coupled material. The approach is applicable to modeling a broad range of material behavior, including repolarizations in ferroelectrics as well as ferroelectric-antiferroelectric phase transitions in electroceramics such as lead lanthanum zirconate stannate titanate. A 3D 8 node element with nodal displacement and voltage degrees of freedom has been formulated using standard isoparametric shape functions. The elements utilize nonlinear constitutive relations for more accurate representation of material response at high electric fields. The phase/polarization state of the material is represented by internal variables in each element, which are updated at each simulation step based on phenomenological model. The model reproduces strain and electric displacement hysteresis loops observed in the material. The approach allows modeling of complex actuator geometries subject to non-uniform electric fields. An a sample application, the response of a piezoelectric wafer with interdigitated electrodes is analyzed. Such a geometry leads to stresses arising from non-uniform poling in the sample which can be computed using the finite element model.
The paper discusses the objectives, issues and research directions of the ONR program on active materials and adaptive structures. It addresses the mechanics tools necessary for the design of this new class of structu...
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ISBN:
(纸本)0819420905
The paper discusses the objectives, issues and research directions of the ONR program on active materials and adaptive structures. It addresses the mechanics tools necessary for the design of this new class of structures. The paper reviews the research in the mechanics of materials of high strain active materials and engineering active materials, hybrid active materials, constitutive modeling, failure of ferroelectric ceramics, and active material interaction with host material. Understanding failure mechanisms in active materials was recognized early in the program to be of great importance to reliable design of high performance actuators and their acceptance by the design community. New concept of engineering active materials, and developments of hybrid active materials are introduced, as means to achieve high performance actuation. The paper covers different design approaches for high strain/high frequency actuators and new actuator concepts and the mechanics of embedding of actuators in composite structures.
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