Matrix second order systems arise in a variety of structural dynamics and control problems. The analysis and design of such systems is traditionally done in frequency domain or in time domain (state space framework). ...
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ISBN:
(纸本)0819417912
Matrix second order systems arise in a variety of structural dynamics and control problems. The analysis and design of such systems is traditionally done in frequency domain or in time domain (state space framework). The formulation of the control design problem in matrix second order form (i.e., configuration space framework) has many advantages over first order state space form. In this paper, a novel approach for designing a stabilizing controller in a second-order model of piezoelectrically controlled flexible beam is proposed.
Transverse piezoelectric mode ceramic-polymer composites provide several advantages over conventional longitudinal mode composites. It has been shown, from both analytical and experimental results, the hydrostatic per...
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ISBN:
(纸本)0819417912
Transverse piezoelectric mode ceramic-polymer composites provide several advantages over conventional longitudinal mode composites. It has been shown, from both analytical and experimental results, the hydrostatic performance of 1 - 3 tubular and 2 - 2 plate piezocomposites can be significantly improved by utilizing the transverse piezoelectric effect. By varying the geometry of the piezoelectric ceramics and the configuration of constituent phases, the undesirable components of piezoelectric response of the composites can be eliminated. Moreover, the effective uniaxial and hydrostatic responses can be greatly enhanced by optimizing the physical properties of the constituent phases and the structures of the composites.
Actuators and/or sensors embedded into a host material will disrupt the physical properties of the host. Finite element analysis was used to determine and to minimize the stress concentrations which arise in a `smart&...
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ISBN:
(纸本)0819417912
Actuators and/or sensors embedded into a host material will disrupt the physical properties of the host. Finite element analysis was used to determine and to minimize the stress concentrations which arise in a `smart' material system due to the embedded optical fiber sensor. A parametric study was undertaken to determine the theoretical mechanical properties of the interface coating that minimizes the disruption of the host material properties due to the optical fiber inclusion. The effects of transverse tensile and thermal loading were studied, and also the residual thermal stress concentrations due to the manufacturing process were taken into consideration. The stress concentrations in the composite host are affected by the dimensions and mechanical properties of the interface coating. The results show that with careful selection of the interface coating properties the stress concentrations in the host material caused by the optical fiber inclusion can be reduced and be similar to those of the pure host material.
This paper focuses on the curriculum development portion of an ongoing project whose goal is to integrate research results with curriculum development in the area of smartstructures. These courses are intended for se...
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This paper focuses on the curriculum development portion of an ongoing project whose goal is to integrate research results with curriculum development in the area of smartstructures. These courses are intended for seniors and graduate students in Electrical, Mechanical and Aerospace Engineering and Engineering Mechanics. Two courses, each with a laboratory component, have been developed and taught during the spring and fall semesters in 1994. The topics covered include some review in mechanics of materials and linear system theory, sensors, actuators, advanced topics in vibrations, control, system identification, and composite materials in the first course. The second course treats structural control techniques, active and passive damping using piezoceramic actuators, modeling and control of distributed systems, and neural networks for smartstructures. Both courses are team-taught by two instructors, one from the Department of Electrical Engineering and one from the Department of Mechanical and Aerospace Engineering.
A new class of materials called smart tagged composites has great potential for use in structural health monitoring. This paper introduces concepts and interrogation schemes for piezoelectric tagged composite material...
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ISBN:
(纸本)0819417912
A new class of materials called smart tagged composites has great potential for use in structural health monitoring. This paper introduces concepts and interrogation schemes for piezoelectric tagged composite materials. Experiments were undertaken to demonstrate the feasibility of piezoelectric tagging by incorporating PZT-5A particles into a polyester matrix. Several types of diametral compression specimens were fabricated and tested to failure while monitoring the induced charge across electrodes placed on the front and back faces of the specimens. The effect of volume fraction of piezo particles and glass reinforcement was investigated along with connectivity of the piezo phase. Small amounts of graphite were added to some specimens to aid in the poling process, however this proved to be of little benefit. The greatest sensitivity and highest induced fields were obtained for a pseudo 1 - 3 piezocomposite system with 6% volume fraction loading of the piezo phase.
A methodology is proposed for designing a structure and robust control for optimum performance. The problem is formulated as a nonlinear mathematical optimization problem with structural weight as the objective functi...
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ISBN:
(纸本)0819417912
A methodology is proposed for designing a structure and robust control for optimum performance. The problem is formulated as a nonlinear mathematical optimization problem with structural weight as the objective function and constraints within the realm of structural and control design requirements. The control approach selected for this investigation is based on multi-input multi-output H2 - H∞ theory which can tolerate structured and unstructured uncertainties. The constraints were imposed on the structural frequencies and gain separation between open-loop and closed-loop systems. The application of the design methodology is illustrated on a wing box idealized with bar elements and composite box-beam.
The sensor response of a piezoelectric transducer embedded in a fluid loaded structure is modeled using a hybrid numerical approach. The structure is excited by an obliquely incident acoustic wave. Finite element mode...
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ISBN:
(纸本)0819417912
The sensor response of a piezoelectric transducer embedded in a fluid loaded structure is modeled using a hybrid numerical approach. The structure is excited by an obliquely incident acoustic wave. Finite element modeling in the structure and fluid surrounding the transducer region is used and a plane wave representation is exploited to match the displacement field at the mathematical boundary. On this boundary, continuity of field derivatives is enforced by using a penalty factor. Numerical results are presented for the sensor response in different host materials piezoelectric sensor materials. It is found that the sensor at that location is not only non-intrusive but also sensitive to the characteristic of the structure.
This paper deals with the problems of converting a continuous- time uncertain system to an equivalent discrete-time interval model and constructing a robust hybrid control law for an uncertain sampled-data system. The...
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ISBN:
(纸本)0819417912
This paper deals with the problems of converting a continuous- time uncertain system to an equivalent discrete-time interval model and constructing a robust hybrid control law for an uncertain sampled-data system. The system matrices characterizing the state-space representation of the original uncertain materials and structures are assumed to be interval matrices. The Pade approximation method together with interval arithmetic is employed to obtain the approximate discrete-time interval models. A technique is developed to estimate the less conservative modeling errors. These modeling errors are used to modify the obtained Pade interval approximants. The resulting modified interval models are able to tightly enclose the exact discrete- time uncertain model. Various digitally redesigned nominal controllers, which are developed for digital control of continuous-time nominal systems, are extended to the corresponding interval controllers for robust digital control of continuous-time uncertain systems. Using the digitally redesigned interval controllers, the dynamic states of the digitally controlled sampled-data uncertain systems are able to closely match with those of the original analogously controlled continuous-time uncertain systems for a relatively longer sampling period.
In this paper, we discuss the use of new methods from robust control and especially H∞ theory for the explicit construction optimal feedback compensators for several practical distributed parameter systems. Indeed, b...
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ISBN:
(纸本)0819417912
In this paper, we discuss the use of new methods from robust control and especially H∞ theory for the explicit construction optimal feedback compensators for several practical distributed parameter systems. Indeed, based on operator and interpolation theoretic methods one can now solve the standard H∞ control problem for a broad class of systems modelled by PDEs. On our approach, the complexity of the computations involved is only a function of the weighting filters, and not the state space dimension which is why we can handle infinite dimensional systems with no approximations involved. These techniques are based on certain operator theoretic notions connected with a class of operators which we call skew Toeplitz. These are precisely the operators which appear in the H∞ optimization problem.
The goal of this paper is to examine the benefits of integrated control/structure design optimization using covariance control in the presence of saturation limits and performance robustness. A key element of this app...
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ISBN:
(纸本)0819417912
The goal of this paper is to examine the benefits of integrated control/structure design optimization using covariance control in the presence of saturation limits and performance robustness. A key element of this approach is the use of a covariance parameterization of the control law, allowing saturation and performance robustness to be easily included. The controller design variables are the elements of the Cholesky decomposition of the closed loop system covariance matrix. Applying the approach to an example from the literature it was found that the total structural mass and the control effort were reduced while output rms for the nominal model was decreased. In addition, the optimizer was also able to meet the performance robustness constraints while reducing the performance robustness control effort measure. In examining the results, it was found that the optimizer judiciously altered the closed-loop system by adding phase between the modal resonance frequencies to improve the overall broad-band performance and to help with improving the robustness of the system.
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