This paper discusses the Adaptive Neural control (ANC) Architecture for on-line system identification and adaptive control. After reviewing results to-date involving control of structural vibration, we describe extens...
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ISBN:
(纸本)0819417912
This paper discusses the Adaptive Neural control (ANC) Architecture for on-line system identification and adaptive control. After reviewing results to-date involving control of structural vibration, we describe extensions of the ANC architecture to handle adaptive control of smartstructures involving large numbers of distributed actuators and sensors.
An individual blade controller designed to attenuate the aeroelastic response of helicopter rotors in forward flight by tailoring the blade root attachment conditions is developed. A feasibility analysis indicates tha...
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ISBN:
(纸本)0819417920
An individual blade controller designed to attenuate the aeroelastic response of helicopter rotors in forward flight by tailoring the blade root attachment conditions is developed. A feasibility analysis indicates that the open-loop controller which incorporates both passive and active design techniques is energy efficient and may be realized by available adaptive structures.
The field of smartstructures encompasses a large number of engineering disciplines. A clear understanding of the concepts of smartstructures depends on in depth knowledge of mechanics of materials, mechanical vibrat...
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ISBN:
(纸本)0780324463
The field of smartstructures encompasses a large number of engineering disciplines. A clear understanding of the concepts of smartstructures depends on in depth knowledge of mechanics of materials, mechanical vibrations, structural analysis, sensors and actuators and control theory. This field is truly multidisciplinary in nature and promises many technological innovations. A brief survey of multidisciplinary research in smart structure is provided in this paper.
Ferroelectric crystals are widely used for manufacturing smart actuators owing to their strong electromechanical coupling effect and the prompt response to the applied electric fields. Many ferroelectric actuators are...
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ISBN:
(纸本)0819417912
Ferroelectric crystals are widely used for manufacturing smart actuators owing to their strong electromechanical coupling effect and the prompt response to the applied electric fields. Many ferroelectric actuators are operated under cyclic loading conditions. The cyclic-loading strengths of these materials are, however, substantially lower than their monotonic-loading strengths. It has been observed that the macroscopic properties of these materials deteriorate after a large number of cycles of the applied electric field. This is the so-called electric fatigue. Recent experimental investigations suggest that microcracking may be the major cause of electric fatigue. The authors investigated the interactions of ferroelectric twins with grain boundaries and pre-existing microcracks. They have demonstrated that the stress fields exhibit a power-law singularity at the intersecting points of twinning planes and grain boundaries. This concentration in stresses may initiate microcracks at the intersecting points. They have also shown that the formation of ferroelectric twins at a pre-existing crack tip results in stronger singularities of the stress and electric fields than the common (root)r-singularity. This indicates that the interaction between the ferroelectric twins and the microcracks may promote crack growth.
In order to meet the demands of simplicity and reliability in active control systems for flexible structures, an inexpensive active truss element and control law has been developed in this research. A decentralized sw...
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In order to meet the demands of simplicity and reliability in active control systems for flexible structures, an inexpensive active truss element and control law has been developed in this research. A decentralized switching control law is used along with a compressible fluid in the truss element in order to dissipate energy during the motion of the structure. However, the energy is not absorbed in the Same manner as a conventional viscous damper. The truss element retains its maximum stiffness, but has a reset-able nominal unstressed length. Energy is absorbed in the working fluid of the truss element through heat transfer to the environment when the nominal length is reset at the proper switching times. The control law is insensitive to changes in structural parameters such as mass, stiffness, and damping. In this paper, a mathematical model for the system is presented along with a stability analysis and experimental results.
The fiber-optic Michelson interferometric sensor has been employed to detect the vibration signal of a flexible beam. An active control technique is also implemented to suppress the vibration signal generated from a p...
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The fiber-optic Michelson interferometric sensor has been employed to detect the vibration signal of a flexible beam. An active control technique is also implemented to suppress the vibration signal generated from a piezoelectric transducer. The first four vibration modes and random vibration of a flexible beam have been stabilized successfully.
In this paper, we study a mathematical model which describes a particular fluid/structure interaction system of current interest at the NASA Langley Research Center.
ISBN:
(纸本)0819417912
In this paper, we study a mathematical model which describes a particular fluid/structure interaction system of current interest at the NASA Langley Research Center.
This paper reports the results of our study on structure configurations and material compositions for the construction of smart photonic bandgap structures. The study focuses on the deposition of various Langmuir-Blod...
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ISBN:
(纸本)0819417904
This paper reports the results of our study on structure configurations and material compositions for the construction of smart photonic bandgap structures. The study focuses on the deposition of various Langmuir-Blodgett films for realizing these structures. Multilayer polymeric L-B films using different materials have been deposited and their physical properties studied using atomic force microscopy. Possible causes of film non-uniformity are investigated.
It is well documented that high void content and delaminations are observed during the fabrication of thick carbon/phenolic composites due to the high percentage of volatile release which occurs during polymerization....
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It is well documented that high void content and delaminations are observed during the fabrication of thick carbon/phenolic composites due to the high percentage of volatile release which occurs during polymerization. In order to eliminate these imperfections and enhance product quality for thick carbon/phenolic composites, smart sensors are used to monitor the property changes during the processing and control of the component to minimize this effect. This paper documents an effort to develop a technique to monitor and collect sensor data during the curing process of a general material system. Data obtained from sensors are used to generate an expert processing knowledge base which automatically controls the composite cure state based on direct sensor response, in lieu of classical time/temperature techniques (i.e. recipes). Microdielectric, ultrasonic, thermopile, thermal couple, and Extrinsic Fabry-Perot Interferometer (EFPI) sensors are investigated as potential candidates to monitor and subsequently control the manufacturing process of a composite material. Microdielectric sensors are used to monitor resin property changes such as viscosity and cure index. Ultrasonic sensors are used to measure stiffness changes and porosity development in the composite material. Thermopile and thermal couples are used to monitor temperature variance and heat reaction rates within the material. EFPI sensors, historically used for monitoring structural integrity during service applications (smartstructures), are used to detect local strain changes caused by temperature, pressure, or process induced residual stresses. In addition to classical optical sensors, a modified EFPI thermal sensor is employed to monitor temperature variations.
We investigate the prospects for intelligent control of smart composites (containing sensors, actuators, power supply, and signal conditioning) that are envisioned for applications in rotorcraft systems (rotor blades,...
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ISBN:
(纸本)0819417912
We investigate the prospects for intelligent control of smart composites (containing sensors, actuators, power supply, and signal conditioning) that are envisioned for applications in rotorcraft systems (rotor blades, power shafts, fuselage shell). This paper is concerned with multi-dimensional wavelets and relevant heuristic procedures for fast and parsimonious identification. We also discuss some control techniques based on the idea of a homogeneous system model.
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