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smart structures and materials 1995: mathematics and control in smart structures

作者： Vallone, Phillip Hopkins, Mark A. Eastman Kodak Co. Rochester NY USA

ISBN: (纸本)0819417912

Presented below is a summary of the results obtained to date on the verification of a novel state space model identification technique called PLID (pseudo linear identification), given in Hopkins et al. This technique has several unique features that include: (1) optimal joint parameter and state estimation (that gives rise to its nonlinearities);(2) provisions for sensor, actuator, and state noise;(3) and it converges almost surely to the true plant parameters provided that the plant is linear, completely controllable/observable, strictly proper, time invariant, and all noise sources are zero mean white Gaussian (ZMWG). Experiments carried out on a flexible, modally dense 3-D truss structure standing 4 feet tall have shown PLID to be a robust technique capable of managing significant deviations from the assumptions made to prove strict optimality. Using the 3 actuators and 3 sensors attached to the structure, models varying in size from 24 to 64 states have been used to approximate this infinite dimensional testbed in the frequency range between 50 to 500 Hz. Sensor signals with rms levels of approximately 2 volts have been predicted by PLID to within 0.01 volts rms.

关键词： structures (built objects)

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Analysis of active control with on-line system identification on sound transmission through an elastic plate

Analysis of active control with on-line system identificatio...

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smart structures and materials 1995: mathematics and control in smart structures

作者： Koshigoe, Shozo Teagle, Allen Tsay, Ching-Hsu The Aerospace Corp. El Segundo CA USA

ISBN: (纸本)0819417912

An adaptive control algorithm with on-line system identification capability has been developed. One of the great advantages of this scheme is that an additional system identification mechanism such as an additional uncorrelated random signal generator as the source of system identification [Eriksson and Allie, Acoust. Soc. Am. 85, 797 - 802 (1989)] is not required. A time varying plate-cavity system is used to demonstrate the control performance of this algorithm. The time varying plate-cavity system is used to demonstrate the control performance of this algorithm. The time varying system consists of a stainless steel plate which is simply supported on a rigid cavity where the cavity temperature can depend on time. For a given externally located harmonic sound excitation, the system identification and the control are simultaneously executed to minimize the transmitted sound in the cavity. The control performance of the algorithm is examined for two cases. Keeping the cavity temperature constant for the first case, the external disturbance frequency is swept with 2 Hz/second from below to above a resonance frequency of the plate-cavity system. The simulation shows an excellent frequency tracking capability with cavity internal sound suppression of 40 dB. For the second case, the cavity temperature is lowered to a half of its original value in 60 seconds while the external sound excitation is fixed with a frequency. Hence, the cavity resonant frequency decreased and passes the external sound excitation frequency. The algorithm shows 40 dB transmitted noise suppression without compromising the system identification tracking capability.

关键词： Plates (structural components)

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Mechanical design synthesis from sparse feature-based input

Mechanical design synthesis from sparse feature-based input

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smart structures and materials 1995: mathematics and control in smart structures

作者： Burgett, Steve R. Bush, Roger T. Sastry, S.Shanker Sequin, Carlo H. Univ. of California/Berkeley Berkeley CA USA

ISBN: (纸本)0819417912

We are researching a new paradigm for CAD which aims to support the early stages of mechanical design well enough that designers are motivated to actually use the workstation as a conceptual design tool. At the heart of our approach is shape synthesis, the computer generation of part designs. The need for such automation arises from the fact that any mechanical part is defined by two kinds of geometry: features that are critical to its function (application features), and the material that merely fleshes out the rest of the part (bulk shape). Application features are most often associated with contact surfaces of the part, for example, a bore for a bearing or a mounting surface for a motor. They are the high-level entities in terms of which the designer reasons about the design. Bulk shape must obey certain constraints, such as noninterference with other parts, minimum allowable thickness of the part, etc., but is somewhat arbitrary. We are developing a system wherein the designer inputs the application features, along with topological constraints, degrees of freedom, and boundary volumes, then the bulk shapes of the parts are synthesized automatically. Overall economy is enhanced by reducing the amount of input necessary from the designer, by providing for more complete exploration of the design space, and by enhancing manufacturability and assemblability of the component parts. This paper presents the functional requirements of such a system, and discusses preliminary results.

关键词： structures (built objects)

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Nonlinear analysis of composite strength loss due to embedded ductile metal coated optical fiber sensors

Nonlinear analysis of composite strength loss due to embedde...

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smart structures and materials 1995: mathematics and control in smart structures

作者： Sirkis, James S. Grande, R. Univ. of Maryland/Coll. Park Coll. Park MD USA

ISBN: (纸本)0819417912

The great many advantages to using composite materials in structural applications are often overshadowed by the fact that composites possess relatively low impact resistance and the fact that the damage from impacts is often at a location that makes detection difficult and costly. An inexpensive and reliable method of detecting location and severity of damage in composites would be of great benefit. Embedded optical fibers have previously been used to detect damage using an optical fiber fracture concept, where the optical fiber is intended to fracture at the load that causes damage to the composite host, which in turn prevents light from being transmitted through the fiber. Untreated optical fibers have been embedded in composites subject to loading for this purpose, and the strengths of the optical fibers were found to be such that only severe damage could be detected. To tailor the sensitivity of the fiber, an etching technique was developed to predispose optical fibers to break at a known load. Ductile metallic coated fibers have been suggested as a potential alternative to fiber breakage-type damage sensors, where permanent deformation in the coating is used as a metric of thermal or mechanical overloads. One possible advantage offered by this configuration over etched fibers is that the information includes more than just binary (go or no go) data. The actual magnitude of the event may be recoverable from the residual strain data. If the metal coated optical fiber sensor concept proves feasible for damage detection, then the mechanical and physical attributes that are desirable in a coating must be determined. Sirkis and Dasgupta used non-linear analytical techniques to investigate behavior of a metal coated fiber (not embedded) subjected to axial tension and uniform thermal loading, and found that the concept was feasible. Chang and Sirkis then tested this type of sensor in uniaxial tension and by embedding them in graphite/epoxy plates subjected to impact lo

关键词： structures (built objects)

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Aerospace Thermal structures and materials for a New Era

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丛书名： Progress in Astronautics and Aeronautics

1995年

作者： Earl A. Thornton

ISBN: (数字)9781600866364

ISBN: (纸本)9781563471827

Presenting recent advances in technology for high temperature structures and materials, this book will be of great interest to engineers and material scientists working on advanced aeronautics and astronautics projects that involve elevated temperatures. Other topics discussed include high-speed flight in the atmosphere, propulsion systems, and orbiting spacecraft. The latest research is compiled here in 19 papers written by various experts from all over the world. Complete with figures, graphs, and illustrations, this compilation of research is an essential volume for all engineers and scientists involved in aerospace thermal structures and materials. * Includes hundreds of figures, graphs, and illustrations. * Includes papers by leading experts detail the latest research and innovations. * Essential for all scientists and engineers involved in aerospace thermal structures and materials.

关键词： Acoustics Aeroacoustics Aerodynamics Aeronautical Engineering Aeronautics Aerothermodynamics Airbreathing Jet Engine Aircraft Components and Structure Aircraft Design Aircraft Engines Aircraft Operations and Technology Aircraft Wing Design Aircrafts Alloys Aluminium Alloys Annealing Applied mathematics Beam (structures) Buckling Analysis Combustion Chambers Combustors Composite materials Composite structures Compressors Computational Fluid Dynamics Conservation of Momentum Equations Continuum Mechanics Convection Coolant Cooling Technology Cryogenics Cylindrical Shell structures Deformation Deformation Mechanisms Earth Observation Satellite Energy Energy Conversion Energy Economics Energy Forms, Production and Conversion Equations of Fluid Dynamics Failure Analysis Fatigue (materials) Finite Difference Method Finite Element Method Finite Element Software Flexible and Active structures Flow Regimes Fluid Dynamics Fracture Mechanics Gas Turbine General Physics Glass Fiber Heat Conduction Heat Engines Heat Transfer Heat Treatment Jet Engines Material Properties materials materials Synthesis and Processing materials and Structural Mechanics Mathematical Analysis Mechanical Properties Mechanical and Structural Vibrations Mesh Generation Metal Matrix Composites Metallurgy Metalworking Microscopy Numerical Analysis Plasticity Polymer Matrix Composites Propulsion and Power Quenching Radiative Heat Transfer Rocket Engine Rocketry Satellites Shell structures smart structures and materials Solid Mechanics Space Systems Space Systems and Vehicles Spacecraft Design Spacecrafts Stress-Strain Analysis Structural Analysis Structural Design and Development Structural Engineering Structural Kinematics and Dynamics Structural Material Properties Structural Mechanics Structural System structures, Design and Test Thermal control and Protection Thermal Effects Thermal Insulation Thermal Measurement Thermal Modeling and Analysis Thermodynamic Properties Thermodynamics Thermophysical Properties Thermophysics and Heat Transfer Titanium A

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Vibration control of rotary wings using smart structures

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smart materials and structures 1994年第2期3卷 181-189页

作者： Nitzsche, Fred Breitbach, Elmar DLR-Inst. of Aeroelasticity Goettingen Germany

The problem of vibration reduction of rotary wings in forward flight is studied using the concept of individual blade control. smart structures are used as a means to construct geometric modal filters able to perform independent modal control of the critical modes in the rotating frame. A real time controller that could circumvent the inherent nonlinearities of the system and is intrinsically robust is devised.

关键词： Vibration control

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Modeling and control of smart structures with bonded piezoelectric sensors and actuators: A passivity approach

Modeling and control of Smart structures with bonded piezoel...

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smart structures and materials 1994: mathematics and control in smart structures

作者： Akella, Padma Chen, Xin Hughes, Declan Wen, John T. Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute TroyNY12180 United States

smart structure has become an increasing common term describing a structure embedded or bonded with a large number of light weight active electro-mechanical sensors and actuators. In this paper, we consider the modeling and control issues related to smart structures bonded with piezoelectric sensors and actuators from the passivity view point. We show that when a piezoelectric patch is used both as an actuator and a sensor, the mapping from the voltage input to current output is passive, which implies that any strictly passive feedback controllers is stabilizing. Issues related to the design of the passive feedback controller with performance optimization and controller order reduction are investigated. © 1994 SPIE.

关键词： Piezoelectricity

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H∞ optimal control of smart structures

H∞ optimal control of smart structures

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smart structures and materials 1994: mathematics and control in smart structures

作者： Lashlee, Robert Rao, Vittal Kern, Frank Department of Electrical Engineering Intelligent Systems Center University of Missouri-Rolla RollaMO65401 United States

The design and implementation of control strategies for large, flexible smart structures presents challenging problems. One of these problem areas is the uncertainty of the natural frequencies of the structure. These uncertainties stem from control structure interaction, modelling errors, and parameter variations (such as fuel consumption). They are important because the natural frequencies of flexible structures tend to be lightly damped and closely spaced. Presently, neither the LQG/LTR controller algorithms nor the H∞ controller algorithms can account directly for natural frequency uncertainties and both algorithms suffer drastic performance degradation in the face of these uncertainties. In order to overcome this problem, we developed a new algorithm called H∞ robust control for natural frequency variations (H∞/NF) that includes the knowledge of the natural frequency uncertainty bounds. In addition, we were successful in implementing this algorithm on a flexible smart structure in our laboratory. This smart structure was a cantilever beam that used NiTiNOL shape memory alloy (SMA) actuators. The performance of H∞NF algorithm was compared with the modified LQG/LTR algorithm using a settling time specification. The H∞/NF controller exhibited dramatically reduced sensitivity to natural frequency uncertainty as compared to the modified LQG/LTR controller. An additional problem area when dealing with smart structures is the limited control effort available from actuators. The standard LQG/LTR control algorithm produced controllers that saturated the NiTiNOL actuators used on the test article. To overcome this saturation problem, we used a modified LQG/LTR design algorithm. Because the initial H∞/NF algorithm did not allow the designer to specify available controller effort, we extended the results by including a control effort cost penalty in the H∞/NF algorithm. This algorithm couples a control effort penalty with the H∞/NF algorithm allowing the designer a trade-of

关键词： Natural frequencies

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VIBRATION AND NOISE control IN CIVIL structures BY smart DESIGN 2

VIBRATION AND NOISE CONTROL IN CIVIL STRUCTURES BY SMART DES...

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2nd European Conference on smart structures and materials

作者： ALLAEI, D QRDC INC EXCELSIORMN 55331

ISBN: (纸本)0819417009

In this paper, the results of a feasibility study for developing an efficient and effective design methodology to make systems 'smart by design' is presented. The primary focus is on computer-aided structural design to implement the inter-coupling of modes of vibration and smart devices built in the original design of structures. The conventional add-on elements are replaced by built-in multi tasks components. First, structures are designed so that a major portion of their vibration energy is localized into their non- critical areas and thereby isolate and quieten critical areas. Next, multi tasks smart components are integrated in the most critical locations of the system in order to monitor and maintain the designed vibration characteristics of the system.

关键词： Chemical elements Structural design Fused deposition modeling Computer aided design Mathematical modeling Computer simulations Vibration control smart structures Finite element methods smart materials

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Individual blade control of hinged blades using smart structures

Individual blade control of hinged blades using smart struct...

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作者： Nitzsche, Fred Breitbach, Elmar DLR-Institute of Aeroelasticity Bunsenstraße 10 D-37073 Goettingen Germany DLR-Institute of Structural Mechanics Lilienthalplatz 7 D-38110 Braunschweig Germany

The feasibility of employing piezoceramic smart materials in active control of the higher harmonic vibration of hinged helicopter blades is investigated. The individual-blade-control concept is adopted to build feedback controllers that employ collocated smart sensors and actuators and are optimized to achieve damping augmentation for blade modes that significantly contribute to the airframe dynamic response. The results indicate that there is a parameter that will help the development of efficient smart rotors. © 1994 IOP Publishing Ltd.

关键词： Piezoelectric ceramics

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