Active sound transmission control using a piezoelectric sensor and actuator on a thin plate is investigated experimentally. The plate made of aluminium covers the opening of an acoustic enclosure where a sound source ...
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Active sound transmission control using a piezoelectric sensor and actuator on a thin plate is investigated experimentally. The plate made of aluminium covers the opening of an acoustic enclosure where a sound source is located. The exterior acoustic field is measured by a microphone array, which scans a hemispherical surface. The isolation performance of the passive plate is poor at its resonance frequencies. Sound transmission through the plate is actively controlled at the resonance frequencies. A one-sensor one-actuator control system minimizes the sensor output by applying a proper electric voltage to the actuator. Global sound reduction of 15-22 dB is achieved at the first three resonance frequencies by using the same sensor and actuator. Using a sensor at a different location, a reduction of 9 dB is obtained at a higher frequency. The relation between control performance and the coincidence of the responses of the transmitted sound and the sensor is briefly discussed based on the mode decomposition theory.
The proceedings contains 30 papers. Some of the specific topics discussed are: shape control of an adaptive wing for transonic drag reduction;shape-memory actuated gimbal;vibration suppresion of fixed-time jib crane m...
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ISBN:
(纸本)0819417963
The proceedings contains 30 papers. Some of the specific topics discussed are: shape control of an adaptive wing for transonic drag reduction;shape-memory actuated gimbal;vibration suppresion of fixed-time jib crane maneuvers;active smart material system for buffet load alleviation;remotely queried embedded sensors in composite structures;and multiscale approach to the control of smartmaterials.
A finite element model of a proposed smart material was developed. This is an initial investigation into using a piezoresistive sensor in conjunction with a multilayer ceramic actuator and a resistor network as the co...
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A finite element model of a proposed smart material was developed. This is an initial investigation into using a piezoresistive sensor in conjunction with a multilayer ceramic actuator and a resistor network as the control circuit. A device model, incorporating piezoresistive composites (with orders of magnitude change in resistivity) and piezoelectric actuators has also been constructed. The model accounts for all relevant material properties and configurations. The software also provides a method of optimizing geometry to obtain desired response. At present the 2-D case predicts a material package with a controllable compliance. This can be extended to a 3-D case consistent with available components.
The potential of using volume and shape changes of polymers, gels, and composites as a source of actuating power was evaluated. For an ordinary polymer, volume changes may be induced by simple heating and cooling (the...
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ISBN:
(纸本)0819417963
The potential of using volume and shape changes of polymers, gels, and composites as a source of actuating power was evaluated. For an ordinary polymer, volume changes may be induced by simple heating and cooling (thermal expansion) or by allowing the polymer to undergo physical transitions such as glass transition, melting or crystallization, and solid state phase transformation. Shape changes in shape memory polymers may be obtained by a combination of thermal and deformation treatments. Polymer gels may undergo large continuous or discrete volume changes in response to stimuli such as temperature, solvent concentration, pH value, electric field, and light. A composite/bimetal laminate, when configured in a proper stacking sequence, is capable of generating out-of-plane forces or deflections. When constrained from changing the volume or shape, each class of these materials can exert a great counteracting stress or pressure on the constraining body. when free to expand or contract, the material may be prescribed to undergo a large change in volume or shape. The magnitudes of the counteracting stresses and the percentages of achievable volume or shape changes were calculated for several commonly used gels, piezopolymers and composites/bimetals. Methods and procedures for making these calculations were established.
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.
Under the pressure of bad economic conditions, Chemical Industry and the Polymer Producing Industry in particular, have been focusing on core businesses and several developments in advanced materials have been slowed ...
Under the pressure of bad economic conditions, Chemical Industry and the Polymer Producing Industry in particular, have been focusing on core businesses and several developments in advanced materials have been slowed down. Increased competition from low cost countries imposes rigorous restructuring of the traditional industry. Environmental considerations enhance the pressure even more. While the Polymer Industry is struggling with major restructuring operations, the scientific activities in the field of macromolecules show a tremendous innovative power. Ever increasing molecular control by the use of new catalysts, cooperative supramolecular interactions and controlled building up of 3-dimensional structures, new architectures leading to enhanced performance and completely new properties, development of-functional materials and smartmaterials are hot items at every meeting. The outcome of this situation could be that the world of materials and materials producers will look quite different in the first decade of the next century.
作者：
Su, JHUSN
CTR SURFACE WARFARECARDEROCK DIVSTRUCT ACOUST & HYDROACOUST RES BRANCHBETHESDAMD 20084
A general and systematic approach to controlling the longitudinal load transmissibility in a rod by coupling generalized substructures is presented. This approach illustrates the general concept of 'substructure&#...
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A general and systematic approach to controlling the longitudinal load transmissibility in a rod by coupling generalized substructures is presented. This approach illustrates the general concept of 'substructure' by formulating the active controllers as virtual substructures coupled to the main structure. The dynamics and load transmissibility of a rod are modeled in modal state space form. The three control algorithms IMSC, ELVC and GSLQ are formulated as three different substructures as well as in state space form so that an explicit substructure dynamics can be realized. The performance of the different algorithms is based on the reaction force at the fixed end subject to a disturbance force at the other (free) end. A performance measure is defined as the reaction force ratio of the closed-loop (coupled with the substructure) to the open-loop (without the substructure). The performance of all three controllers or substructures is presented both in frequency and time. This general approach has provided a way to appreciate the effect of any substructure (either a controller or an attached structure) on the main structure. This has an important implication for designing substructures for the desired response of the coupled structure.
The Synthesis and Processing of Intelligent Cost Effective structures (SPICES) program is comprised of a consortium of industrial, academic and government labs to develop cost effective material processing and synthes...
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ISBN:
(纸本)0819417963
The Synthesis and Processing of Intelligent Cost Effective structures (SPICES) program is comprised of a consortium of industrial, academic and government labs to develop cost effective material processing and synthesis technologies to enable new products using active vibration suppression and control devices to be brought to market. Each team member possesses a specialty in the area of smartstructures which has been focused towards the development of several actively controlled smart material systems. Since smartstructures involve the integration of multiple engineering disciplines, it is the objective of the consortium to establish cost effective design processes between this multiorganizational team for future incorporation of this new technology into each members respective product lines. To accomplish this task, the disciplines of materials, manufacturing, analytical modeling, actuation, sensing, signal processing, and control had to be synthesized into a unified approach between all ten consortium members. The process developed for intelligent structural systems can truly be classified as multiorganization/multidiciplined Integrated Product Development. This process is described in detail as it applies to the SPICES development articles and smart material fabrication in general.
Various control methods of rotor blade vibration reduction based on individual blade control are presented and compared. The benchmark model used is based on a four-bladed helicopter at hover conditions. In this paper...
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ISBN:
(纸本)0819417912
Various control methods of rotor blade vibration reduction based on individual blade control are presented and compared. The benchmark model used is based on a four-bladed helicopter at hover conditions. In this paper, three control strategies are investigated: LQR method of feedback control, feedforward control, and hybrid control (a combination of feedback and feedforward control). It was found that the LQR method provided substantial improvements in the system and very low gains. Feedforward control was found to be somewhat less effective and the hybrid control method, which combines both feedforward and LQR feedback methods, was proven to be the most effective method.
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