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smart structures and materials 2000 - mathematics and control in smart structures

作者： Savran, Cagri A. Atalla, Mauro J. Hall, Steven R. Massachusetts Inst of Technology Cambridge MA United States

We describe structural-acoustic control experiments on a model fuselage test-bed, using collocated pairs of piezoelectric sensors and actuators. The test-bed is a hybrid-scaled model fuselage designed to be representative of complex aircraft structures with rib and stringer construction, which results in a structure with high modal density and complex behavior. The sensor/actuator pairs consist of PVDF film and PZT ceramic sheets bonded to the surface of the model fuselage. Closed-loop control of the fuselage skin was carried out with 30 collocated sensor/actuator pairs, covering approximately 10% of the surface area of the test-bed. The disturbance source is a PZT patch bonded to an adjacent panel. Rate feedback was applied to each collocated pair simultaneously (independent loop closure). Accelerometers attached to the panels and microphones located inside the test-bed were used as performance sensors. The experimental results show a reduction of as much as 20 dB in structural acceleration and up to 10 dB of attenuation in the interior acoustic pressure levels at resonant peaks, over the frequency range of 100-2000 Hz.

关键词： Acoustic variables control

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control of sound radiation from an active constrained layer damping treated plate into an acoustic cavity using structural intensity approach

Control of sound radiation from an active constrained layer ...

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smart structures and materials 2000: Damping and Isolation

作者： Azzouz, Mohamed S. Ro, J. Old Dominion Univ Norfolk United States

Considerable attention has been devoted to actively and passively control of the sound radiating from vibrating plates into closed cavities. With the advent of smart materials, extensive efforts have been exerted to control the vibration and sound radiation from flexible plates using smart sensors/actuators. Active Constrained Layer Damping (ACLD) treatment has been used successfully for controlling the vibration of various flexible structures. The treatment provides an effective means for augmenting the simplicity and reliability of passive damping with the low weight and high efficiency of active controls to attain high damping characteristics over broad frequency bands. The proposed study is investigated using a numerically simulated example consisting of an ACLD treated plate/acoustic cavity system excited by a point harmonic force. In this study, an ACLD treated plate/acoustic cavity coupled finite element model is utilized to calculate the structural intensity and sound pressure radiated by vibrating plates. In the passive control, the optimum placements of ACLD patches are determined by structural intensity of ACLD treated plates and compared to the results obtained by modal strain energy approach. The influence on structural intensity of plate due to damping treatment is investigated.

关键词： Acoustic variables control

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Vibration control of a suspension system via a magnetorheological fluid damper

Vibration control of a suspension system via a magnetorheolo...

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5th European Conference on smart structures and materials

作者： Lai, CY Liao, WH Chinese Univ Hong Kong Dept Mech & Automat Engn Smart Mat & Struct Lab Hong Kong Hong Kong Peoples R China

ISBN: (纸本)0819437107

Semi-active control systems are becoming more popular because they offer both the reliability of passive systems and the versatility of active control systems without imposing heavy power demands. It has been found that magneto-rheological (MR) fluids can be designed to be very effective vibration control actuators. MR fluid damper is a semi-active control device that uses MR fluids to produce controllable damping force. The objective of this paper is to study a single-degree-of-freedom suspension system with a MR fluid damper for the purpose of vibration control. A mathematical model of MR fluid damper is adopted. The model is compared with experimental results for a prototype damper through finding suitable model parameters. In this study, a sliding mode controller is developed by considering loading uncertainty to result in a robust control system. Two kinds of excitations are inputted in order to investigate the performance of the suspension system. The vibration responses are evaluated in both time and frequency domains. Compared to the passive system, the acceleration of the sprung mass is significantly reduced for the system with a controlled MR damper. Under random excitation, the ability of the MR fluid damper to reduce both peak response and root-mean-square response is also shown.

关键词： vibration control suspension magnetorheological damper semi-active and sliding mode

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Development of active six-degrees-of-freedom microvibration control system using giant magnetostrictive actuators

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smart materials & structures 2000年第2期9卷 175-185页

作者： Nakamura, Y Nakayama, M Masuda, K Tanaka, K Yasuda, M Fujita, T Fujita Corp Tech Res Inst Kanagawa Japan Tokkyokiki Corp Amagasaki Hyogo Japan Univ Tokyo Inst Ind Sci Minato Ku Tokyo 106 Japan

An active six degrees-of-freedom microvibration control system using giant magnetostrictive actuators is developed in order to realize a microvibration-free space for precision instruments which hate vibration. A giant magnetostrictive actuator is suitable as a displacement actuator for active microvibration control, because it is both compact and durable and also its response against input is fast and reliable. The developed device consists of a table, six air springs, eight magnetostrictive actuators and six accelerometers on the table. Four actuators are set in the horizontal directions, and another four in the vertical direction. Since air springs and actuators as a unit of vertical support system are arranged in parallel, readjustment of the system is quite easy, even when the operating load an the table is changed. The dimensions of the table are 2000 mm length, 1400 mm width, 230 mm height and a weight of about 2 tons. The operating load on the table is 2 tons. A giant magnetostrictive rod is 6 mm in diameter and 50 mm long. The actuators operate within the stroke range of +/-25 Cc m. A feedback control strategy using only six components of table acceleration on the table is adopted and the controller is designed by a model matching method. The obtained control performance of the system through two vibration control tests can be summarized as follows (1) Root-mean-square values of the table accelerations under micro-tremor are reduced to one-third to one-tenth of the floor accelerations, and kept less than 0.008 cm s(-2) (2) Induced vibrations by impacts acting on the table disappear in less than 0.05 s.

关键词： actuators Air springs System performance Tables giant magnetostrictive microseismic activity Precision instrument Traverse grinding Workload

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Wing shaping for optimum roll performance using independent modal-space control technique

Wing shaping for optimum roll performance using independent ...

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smart structures and materials 2000 - mathematics and control in smart structures

作者： Khot, N.S. Oz, H. Wright-Paterson AFB OH United States

A technique for deforming a flexible wing to achieve a specified roll rate within a specified time at different Mach Numbers is examined. Rather than using an aileron system for roll, antisymmetric elastic twist and camber is determined to achieve the required rolling moment for a specified roll rate. The elastic twist and camber is achieved by providing a system of actuating elements distributed within the internal substructure of the wing to provide control forces. The modal approach is used to develop the dynamic equilibrium equations which culminates in the steady roll maneuver of a wing subjected to aerodynamic loads and the actuating forces. The distribution of actuating forces to achieve the specified steady flexible roll rate within a specified time was determined by using Independent Modal-Space control (IMSC) design approach. Here, a full-scale realistic wing is considered for the assessment of the strain energy required to produce the antisymmetric twist and camber deformation to achieve the specified roll performance.

关键词： Wings

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Active control of wind-tunnel model aeroelastic response using neural networks

Active control of wind-tunnel model aeroelastic response usi...

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smart structures and materials 2000 - Industrial and Commercial Applications of smart structures Technologies

作者： Scott, Robert C. NASA Langley Research Cent Hampton United States

Under a joint research and development effort conducted by the National Aeronautics and Space Administration and The Boeing Company (formerly McDonnell Douglas) three neural-network based control systems were developed and tested. The control systems were experimentally evaluated using a transonic wind-tunnel model in the Langley Transonic Dynamics Tunnel. One system used a neural network to schedule flutter suppression control laws, another employed a neural network in a predictive control scheme, and the third employed a neural network in an inverse model control scheme. All three of these control schemes successfully suppressed flutter to or near the limits of the testing apparatus, and represent the first experimental applications of neural networks to flutter suppression. This paper will summarize the findings of this project.

关键词： Flutter (aerodynamics)

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Vibration distribution reconstruction and control of a thin plate by using distributed PVDF sensors affixed to the plate

Vibration distribution reconstruction and control of a thin ...

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smart structures and materials 2000 - mathematics and control in smart structures

作者： Nagayasu, Katsuyoshi Uchida, Norio Hayashi, Takuro Takahashi, Hiroshi Toshiba Corp Kanagawa Japan

In this study, vibration distribution of a thin plate is detected using outputs from a number of long-span piezoelectric films that serve as distributed vibration sensors affixed on the plate. Using long-span piezoelectric films, only the integrated strains along the direction of the sensor span could be obtained. However, in the case that plural sensors were affixed and a kind of transformation was used, the vibration distribution could be obtained. We are considering applying the method for vibration control of space structures, namely antennas and/or solar battery paddles. In this study, basic technology for realizing the applications is presented. The strain distributions and the sensor outputs are predicted and calculated using NASTRAN (Finite Element Method). The strain distributions of a vibrating rectangular thin plate to which a number of long-span PVDF films were affixed are detected by experiment. These PVDF films are cut into several kinds of sinusoidal shapes and the outputs of the films are composed to the vibration distribution. This method is based on the theory that waves of any kind are composed by the sum of trigonometric function series. The usefulness of this approach is confirmed by comparing the calculational and experimental results.

关键词： Sensors

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Active control system for a rotor blade trailing-edge flap

Active control system for a rotor blade trailing-edge flap

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smart structures and materials 2000 Conference

作者： Duvernier, M Reithler, L Guerrero, JY Rossi, R AEROSP MATRA CCR F-92152 Suresnes France

ISBN: (纸本)0819436038

Reducing the external noise is becoming a major issue for helicopter manufacturers. The idea beyond this goal is to reduce or even avoid the blade vortex interaction (BVI), especially during descent and flights over inhabited areas. This can be achieved by changing locally the lift of the blade. Several strategies to reach this goal are under investigation at EUROCOPTER such as the control of the local incidence of the blade by a direct lift flap. AEROSPATIALE MATRA Corporate Research Centre and AEROSPATIALE MATRA MISSILES proposed an actuator system able to answer EUROCOPTER's needs for moving a direct lift flap. The present paper describes the definition, manufacturing and testing of this new actuator system. This actuator is based on an electromagnetic patented actuation system developed by AEROSPATIALE MATRA MISSILES for missile and aeronautic applications. The particularity of this actuator is its ability to produce the desired force on its whole range of stroke. The flap is designed to be fitted on a DAUPHIN type blade produced by EUROCOPTER and the actuator system was design to fit the room available within the blade and to produce the right amount of stroke and force within the required frequency range. Other constraints such as centrifugal loading were also taken into account. This paper describes briefly the specifications and the major characteristics of the actuating system and presents some results of its behaviour on a representative composite test-bed manufactured by EUROCOPTER when subjected to realistic mechanical loads.

关键词： helicopter active control noise vibration actuator electromagnetic BVI direct lift flap blade

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Air flow control systems for miniature fuel cells

Air flow control systems for miniature fuel cells

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smart structures and materials 2000 Conference

作者： Leo, DJ Nasser, K Virginia Polytech Inst & State Univ Dept Mech Engn Ctr Intelligent Mat Syst & Struct Blacksburg VA 24061 USA

ISBN: (纸本)0819436038

The feasibility of utilizing piezoelectric actuators for air flow control of low-power fuel cells is assessed using an electromechanical model of the actuator and a steady-state model for compressible flow. Expressions for electromechanical efficiency are derived using one-dimensional transducer equations of a. piezoelectric actuator coupled to the pressure-volume relationships for an ideal gas. The derivation demonstrates that the mechanical power output and electrical power requirements of the system are a function of the input-output force ratio;the input force normalized to the blocked force of the actuator, and the piezoelectric coupling coefficient. The mechanical efficiency of the closed cycle is constant at 28.6% and the electrical efficiency varies from less than 1% for a coupling coefficient of 0.1 to approximately 8% for a coupling coefficient of 0.5, Expressions for the force: displacement, and work performed during each process of the four-stroke cycle are derived. A numerical example of a 50 Watt fuel cell demonstrates that only 219 mW of real mechanical pou er is required to deliver the necessary air flow to the fuel cell. Operating frequencies are approximately 600 Hz for actuators with 1 mm free displacement. Dissipation in the power electronics is between 6 and 19 Watts for linear amplifiers but can be reduced to less than 2 Watts for more efficient switching-type power conditioners. This example demonstrates that piezoelectric actuators are a viable technology for fuel cell air flow control when they are used in conjunction with efficient power electronics.

关键词： Actuators control systems Hydrogen Electronics Amplifiers Mechanical efficiency Electrical efficiency Energy efficiency Oxygen Mechanical engineering

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Fabrication of high-performance PZT actuator using microwave sintering process

Fabrication of high-performance PZT actuator using microwave...

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smart structures and materials 2000 - Active materials: Behavior and Mechanics

作者： Takahashi, Hirofumi Kato, Kazuaki Qiu, Jinhao Tani, Junji Fuji Ceramics Corp Fujinomiya-City Japan

Recently, high-performance piezoelectric actuators with larger force and displacement output are being studied by many researchers due to their prospective application in smart material and structural systems, especially for vibration and noise control. The improvement of performance is achieved by the improvement on material composite, sintering process, and actuator structures. On the other hand, studies have also been carried out on the application of microwave sintering process in the sintering of ceramic materials. In this study, the application of 28 GHz microwave sintering process in the sintering of PZT materials was tried and sintering conditions were intensively investigated. Microwave sintering offers advantages over conventional technologies, such as repression of grain growth due to rapid heating, and improvement of microstructure to internal heating. As a result, the sintering time of PZT materials using 28 GHz microwave was reduced to 1/10 of the time needed for the conventional sintering process, with improvements on the properties such as electromechanical coupling factor, and piezoelectric constants. Furthermore the performances of the actuators fabricated with the microwave sintering process were evaluated in a vibration test and compared with the performances of the actuator fabricated with the traditional sintering process, and the performance superiority was confirmed.

关键词： Intelligent structures

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