During the past decade, the multi-disciplinary field of smartmaterials and structures has experienced rapid growth in terms of individual technologies and applications. The integration of sensors, actuators, and cont...
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During the past decade, the multi-disciplinary field of smartmaterials and structures has experienced rapid growth in terms of individual technologies and applications. The integration of sensors, actuators, and controllers with structures that enable adaptation to environmental and operational conditions has progressed to such a point that numerous systems applications are being demonstrated. This paper reviews a few of these projects, specifically focusing on demonstrations and relevant characterization and testing in the following areas: noise and vibration suppression and shape control concepts for spacecraft and launch vehicles, aircraft, and rotorcraft. These projects are focused on showing potential system-level performance improvements using smart technologies in realistic sub- and full-scale structures. The status of smartmaterials and actuator technologies, critically important to achieving the ultimate objective of a "smart" system, is also addressed in some detail.
The distributed vibration sensing and control of a piezoelectric laminated curved beam are studied. The mathematical model of a curved beam with a distributed piezoelectric sensor and actuator is formulated first, fol...
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The distributed vibration sensing and control of a piezoelectric laminated curved beam are studied. The mathematical model of a curved beam with a distributed piezoelectric sensor and actuator is formulated first, followed by vibration analysis. This model provides estimates of the sensor signal, actuator-induced membrane force, and actuator-induced bending moment, as well as predicting the controlled damping ratio and dynamic response. The sensor sensitivity with various sensor thicknesses is studied and compared. The effectiveness of active damping controls is evaluated with respect to different beam thickness, and sensor/actuator thickness. Numerical examples are provided and simulation results are discussed.
The present research experimentally investigates the feasibility of a trailing-edge flap mechanism actuated in a helicopter rotor by piezoelectric stacks in conjunction with a dual-stage mechanical stroke amplifier to...
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The present research experimentally investigates the feasibility of a trailing-edge flap mechanism actuated in a helicopter rotor by piezoelectric stacks in conjunction with a dual-stage mechanical stroke amplifier to actively control vibration. A new mechanical leverage amplification concept was developed to extend the capability of a simple lever-fulcrum stroke amplifier. A refined prototype actuator and flap mechanism were designed and fabricated using five piezostacks. The bench-top test of the actuator showed 73.7 mils of free stroke and uniform displacement output up to a frequency of 150 Hz. Spin testing was performed in the vacuum chamber to evaluate the performance in rotating environment, and the refined prototype actuator showed approximately 13% loss in actuation stroke at 710g of full-scale centrifugal loading. In the Open-Jet wind tunnel testing to simulate the aerodynamic loading environment, the peak-to-peak flap deflections above 8 degrees for freestream velocity of 120 ft/sec were obtained at different excitation frequencies. It demonstrated the capability of the refined prototype actuator in rotating environment to potentially reduce helicopter vibration.
In this paper the dynamic strain response of a piezoelectric material subjected to an electron beam charge input is examined. A piezoelectric material plate (PZT5h) was prepared with a single distributed electrode on ...
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In this paper the dynamic strain response of a piezoelectric material subjected to an electron beam charge input is examined. A piezoelectric material plate (PZT5h) was prepared with a single distributed electrode on one face and the second face subjected to a variety of electron beam inputs. Strain gages were attached atop the electrode to measure the strain response due to the combined effects of the electrode potential and the charge from the electron gun. When the electrode potential is stepped from 0 to 100 volts the strain needs only 1 second to reach steady state position, but when the electrode potential is stepped down it needs almost 1 minute to reach steady state. This phenomenon can be explained as follows: raising the electrode potential increases the energy of the electrons, so the secondary electron yield falls well below one and negative charge builds up quickly. Dropping the electrode potential decelerates the incoming beam, so the secondary yield becomes only slightly higher than one, so the negative charge decreases at a much lower rate, thus it takes longer to reach steady state.
A systematic method is presented for optimal integration of smart (active) materials based actuators into the structure of robot manipulators for the purpose of minimizing the high harmonic components of the required ...
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A systematic method is presented for optimal integration of smart (active) materials based actuators into the structure of robot manipulators for the purpose of minimizing the high harmonic components of the required actuating torques (forces). The approach is based on the Trajectory Pattern Method (TPM). With properly synthesized low harmonic motion trajectories and by minimizing the high harmonic components of the required actuating torques with properly sized and placed smart actuators, such computer controlled machines can operate at higher speeds, greater tracking precision and minimal vibration and control problems.
A fuzzy finite element based approach is developed for modelling smartstructures with vague or imprecise uncertainties. Fuzzy sets are used to represent the uncertainties present in the piezoelectric, mechanical, the...
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A fuzzy finite element based approach is developed for modelling smartstructures with vague or imprecise uncertainties. Fuzzy sets are used to represent the uncertainties present in the piezoelectric, mechanical, thermal, and physical properties of the smart structure. In order to facilitate efficient computation, a sensitivity analysis procedure is used to streamline the number of input fuzzy variables, and the vertex fuzzy analysis technique is then used to compute the possibility distributions of the responses of the smart structural system. The methodology has been developed within the framework of the smartCOM computational tool for the design/analysis of smart composite structures. The methodology developed is found to be accurate and computationally efficient for solution of practical problems.
A procedure to determine controller parameters using principles from Internal Model control (IMC) in combination with Quantitative Feedback Theory (QFT) for robust vibration control of flexible mechanical structures i...
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A procedure to determine controller parameters using principles from Internal Model control (IMC) in combination with Quantitative Feedback Theory (QFT) for robust vibration control of flexible mechanical structures is presented. This design process is demonstrated using a simply structured plant as an example. Through this example, the important features of the design process are illuminated.
This paper develops and demonstrates performance analysis of vibration suppression and damage detection control laws on structures with fatigue cracks. State feedback control laws for the individual tasks of vibration...
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ISBN:
(纸本)0819436038
This paper develops and demonstrates performance analysis of vibration suppression and damage detection control laws on structures with fatigue cracks. State feedback control laws for the individual tasks of vibration suppression and autonomous damage detection are designed based on low-order models of a damaged structure. These control laws are applied to finite-element models of structures with through-surface and surface cracks. The analysis ascertains the ability of feedback control to enhance sensitivity of modal frequency shifts due to realistic damage and the potential for using the same sensors and actuators for implementing vibration damping control laws that are insensitive to damage. In the control model, damage consists of simple reductions in thickness over a small area of the structure. Finite-element models to which control laws are applied are developed using commercial software (ABAQUS) that more accurately models the crack by releasing element connections or by using line spring elements. Results show that feedback control laws can be designed for either crack detection or vibration suppression using identical hardware. In addition. we demonstrate that simple models of damaged structures are suitable for designing control laws for detecting more complex damage conditions, and we demonstrate the use of commercial software for model-based simulation of controlled structures.
This paper shows how the geometrically exact quasilinear equations of motion of nonlinearly elastic and viscoelastic rods and shells whose response is sensitive to ambient magnetic, electric, or thermal fields can be ...
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This paper shows how the geometrically exact quasilinear equations of motion of nonlinearly elastic and viscoelastic rods and shells whose response is sensitive to ambient magnetic, electric, or thermal fields can be converted to semilinear or linear equations by suitable feedback controls of the ambient fields. Indeed, in certain cases, the feedback can make the response of a nonhomogeneous structure be like that of a homogenous structure, enlarge or diminish the isotropy group of the structure, increase or decrease the internal dissipation in the structure, and cause naturally different wave speeds to be the same. The availability of such controls indicates that the shocks to which quasilinear hyperbolic partial differential equations for nonlinear elastic structures are susceptible need cause no difficulty in control problems. In particular, if the structure is subject to additional controls that cause it to perform specific tasks, then these additional controls are treated by the theory for (semi)linear partial differential equations, for which there is an extensive development.
Shape Memory Alloys (SMAs) have become increasingly attractive as embedded actuators in polymers yielding adaptive composite structures. In particular, SMA-elements have been used to actively or passively control shap...
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Shape Memory Alloys (SMAs) have become increasingly attractive as embedded actuators in polymers yielding adaptive composite structures. In particular, SMA-elements have been used to actively or passively control shape, elastic modules, internal stress level and damping capacity of such smart composites. In the passive approach, copper-base SMA-plates can be used as temperature-sensitive damping elements, an interesting solution to improve the vibrational behaviour of alpine skis for example. Active materials are obtained by the integration of pre-strained Ni-Ti-base thin wires in polymer matrix composites enabling control of the vibrational behaviour through the recovery-stress tuning technique. In this paper, some results of national research programmes in Belgium and Switzerland, mainly concerning the damping capacity, are shown and a new European project entitled "Adaptive Composites with Embedded Shape Memory Alloy Wires" is presented in which partners from Belgium, Germany, Greece, Great Britain and Switzerland are collaborating.
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