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Displacement control of Timoshenko beams via induced strain actuators

smart materials AND structures 2000年第6期9卷 981-984页

作者： Ang, KK Reddy, JN Wang, CM Natl Univ Singapore Dept Civil Engn Kent Ridge 119260 Singapore Texas A&M Univ Dept Mech Engn College Stn TX 77843 USA

In this study, analytical solutions for the length and position of strain-induced patch actuators for the static adjustments of beam deflections an presented. To obtain precise deflection control, the Timoshenko beam theory has been adopted. The analytical solutions are derived conveniently by making use of exact relationships between the bending solutions of the Timoshenko beam theory and corresponding quantities of the Euler-Bernoulli beam theory. Examples of point deflection control for shear deformable beams subject to various loads are presented to illustrate the use of the analytical solutions derived. The significance of the contribution of transverse shear deformation effects on the control of beam deflection is discussed.

关键词： Beams and girders

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Active deformable sheets: prototype implementation, modeling and control

Active deformable sheets: prototype implementation, modeling...

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smart structures and materials 2000 Conference

作者： Lind, RJ Johnson, N Doumanidis, CC Tufts Univ Dept Mech Engn Medford MA 02155 USA

ISBN: (纸本)0819436038

Active deformable sheets are integrated smart planar sheet structures performing off-plane deformations under computer actuation and control, to take up a desired dynamic morphology specified in CAD software or obtained by 3-D scanning of a solid surface. The sheet prototypes are implemented in the laboratory by elastic neoprene foil layers with embedded asymmetric grids of SMA wires (Nitinol), which upon electrical contraction bend the sheet to the necessary local curvature distribution. An analytical model of such prototypes, consisting of an electrical, a thermal, a material and a mechanical module, as well as a more complex finite element thermomechanical simulation of the sheer structure have been developed and validated experimentally. Besides open-loop control of the sheet curvatures by modulation of the SMA wire actuation current, a closed-loop control system has been implemented, using feedback of the wire electrical. resistance measurements in real time, correlating to the material transformation state. The active deformable sheets are intended for applications such as reconfigurable airfoils and aerospace structures, variable focal length optics and electromagnetic reflectors, flexible and rapid tooling and microrobotics.

关键词： shape memory alloys composite materials rapid prototyping active deformable sheets

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Integrated structure/control design of micro-positioner for boring bar tool insert

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Proceedings of SPIE - The International Society for Optical Engineering 2000年 3985卷 560-571页

作者： O'Neal, George P. Pasek, Zbigniew J. Min, Byung-Kwon Koren, Yoram Univ of Michigan Ann Arbor United States

Previous papers by these authors presented an effort to develop a prototype boring tool, utilizing a piezoelectric actuator and photosensitive detectors to actively control a cutting insert. This paper describes an effort to redesign the system using an integrated structural/control methodology. The purpose of the micro-positioner is to improve precision by: i) isolating the finish cutter from tool vibrations, ii) absorbing energy from the tool during rough cuts, and iii) compensating for small geometric or thermal errors. These characteristics enable tools with large length to diameter ratios (L/D) without loss in machining precision, and facilitate automated tool changes. The integrated structural/control design variables consist of the structural shape of the mechanism, including the piezoelectric actuator, and the controller feedback gains. The design variables are determined simultaneously in a single optimization problem. The objective and constraints equations quantify system performance, stability, actuator saturation, and life expectancy as explicit functions of the design variables. The proposed integrated methodology both simplifies the design process of the prototype boring tool, and improves the performance over the original design, as shown by simulation results.

关键词： Integrated control

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Active vibration control of smart composite plates using self-adaptive neuro-controller

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smart materials & structures 2000年第2期9卷 197-204页

作者： Valoor, MT Chandrashekhara, K Agarwal, S Univ Missouri Dept Mech & Aerosp Engn & Engn Mech Rolla MO 65409 USA Univ Missouri Dept Elect & Comp Engn Rolla MO 65409 USA

A neural network-based control system is developed for self-adapting vibration control of laminated plates with piezoelectric sensors and actuators. The conventional vibration control approaches are limited by the requirement of an explicit and often accurate identification of the system dynamics and subsequent 'offline' design of an optimal controller. The present study utilizes the powerful learning capabilities of neural networks to capture the structural dynamics and to evolve optimal control dynamics. A hybrid control system developed in this paper is comprised of a feed-forward neural network identifier and a dynamic diagonal recurrent neural network controller. Sensing and actuation are achieved using piezoelectric sensors and actuators. The performance of the hybrid control system is tested by numerical simulation of a composite plate with embedded piezoelectric actuators and sensors. Finite-element equations of motion are developed based on shear deformation theory and implemented for the plate element. The dynamic effects of the mass and stiffness of the piezoelectric patches are considered in the model. Numerical results are presented for a Rat plate. A robustness study including the effects of structural parameter variation and partial loss of the sensor and actuator is performed. The hybrid control system is shown to perform effectively in all of these cases.

关键词： actuators Hybrid control systems COMPOSITION BOARD vibration control Equations of motion parameter variation dynamic structural analysis Activation diagonal recurrent neural network System dynamics Sensors Piezoelectric sensors Neural network

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Actuator environmental stability

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Proceedings of SPIE - The International Society for Optical Engineering 2000年 3985卷 652-659页

作者： Yoshikawa, Shoko Farrell, Michael Active Control eXperts Inc Cambridge United States

Various configurations of piezoelectric high strain actuators are available in the market. The influence of humidity at high temperature is not well documented, even though it is an important consideration for actuator performance. This paper describes the testing and results of two different families of actuators; QuickPack products and multilayer actuators, tested under two environments; room temperature low humidity and elevated temperature and humidity (80°C/80%RH). A constant DC load was applied to the QP10N and QP10Ni products in free condition, while positive only AC field was applied to multilayer actuators, under pre-stressed condition. High field IR was used as the main tool to determine the health of QuickPack products, whereas, in-situ displacement was measured to monitor the health of multilayer actuators. As expected, in both families of actuators, it was shown that the actuator life is significantly reduced when specimens are exposed to humidity at elevated temperature. Improvement of the humidity barrier, thus less moisture penetration, even when electrodes do not contain silver, is expected to prolong life of actuators.

关键词： Actuators

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Recent advances in smart-material rotor control actuation.

Recent advances in smart-material rotor control actuation.

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AIAA/ASME/ASCE/AHS/ASC 41st structures, Structural Dynamics, and materials Conference

作者： Giurgiutiu, V Univ S Carolina Dept Mech Engn Columbia SC 29208 USA

This paper reviews recent achievements in the application of active-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed wing aircraft. A brief review of the induced-strain actuation principles and capabilities is done first. Attention is focused on the smart rotor-blade applications. The induced twist, active blade tip, and active blade flap concepts are presented and discussed. A number of ingenious displacement amplifications methods, both solid-state and levered, are described. Emphasis is placed on experimental results that prove the expectations and reveal the possible limitations of each particular concept. Full-scale smart rotor efforts are also highlighted. Conclusions and directions for further work are presented.

关键词： Fixed wings

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Active damping enhancement of flexible intelligent truss structures

Active damping enhancement of flexible intelligent truss str...

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smart structures and materials 2000 Conference

作者： Zhang, LM Liu, FQ Nanjing Univ Aeronaut & Astronaut Inst Vibrat Engn Nanjing 210016 Peoples R China

ISBN: (纸本)0819436038

An Modal filter based Independent Modal Space control (IMSC) method is proposed for active damping enhancement of a flexible space intelligent truss structure. Modal Filter (MF) is used to extract modal states from response measurement. The MF is developed for the structures with closely spaced modes, or even repeated frequencies. Modal acceleration can then be extracted form physical acceleration measurements via MF. A modified Leunberger observer is adopted to estimate modal displacement and modal velocity from modal acceleration. The MF-based IMSC method is employed to enhance damping of the space intelligent truss structure with active members. A real-time computer control system is developed to implement the MF-based IMSC strategy. Experimental results demonstrate that the intelligent structure design is successful and the active control method is effective.

关键词： intelligent truss structure damping enhancement modal control active member

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Independent modal space control fidelity for semi-global changes in dynamic properties

Independent modal space control fidelity for semi-global cha...

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smart structures and materials 2000 Conference

作者： Kucuk, H Schultze, JF Michigan Technol Univ Dept Mech Engn Engn Mech Appl Control Res Lab Houghton MI 49931 USA

ISBN: (纸本)0819436038

Much research in this decade has concentrated on the application of modal space control to simplify control design and system monitoring. This investigation will address the fidelity limitations of the modal filter based classical control strategies. Specifically, when the eigen-parameters shift, in concert with semi-global changes in the systems structural properties resulting in similar mode shape but dramatic shift in frequency. Expressly, this examination will concentrate on two spatially similar five bay box trusses of exactly the same geometry (connections and element lengths) and different materials (steel and plastic) and some shift in cross-sectional dimension. The limitation of these parameter shifts should present a practical bound for future application. The investigation incorporated both analytic and experimentally based models of the structural frequency response and residue matrices to analytically model the control problem. The control is investigated for the lower frequency modes due to experimental model limitations. Investigation includes single and multimode control.

关键词： flexible structures active control modal space time-varying fidelity

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Active and passive vibration control of flexible structures using a combination of magnetostrictive and ferro-magnetic alloys

Active and passive vibration control of flexible structures ...

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5th European Conference on smart structures and materials

作者： Bhattacharya, B Vidyashankar, BR Patsias, S Tomlinson, GR Univ Sheffield Dept Mech Engn Sheffield S10 2TN S Yorkshire England

ISBN: (纸本)0819437107

A combined passive and active damping strategy is proposed to control vibration in structures using a combination of layers of ferro-magnetic (passive) damping and smart (active) magnetostrictive material (Terfenol-D). Two types of combined damping systems are considered viz., a noninteractive system and an interactive or hybrid system. Numerical investigations on a cantilever beam model are carried out to investigate various aspects in combined damping scenario. Using variational principle, a beam Finite Element is developed to study the dynamic characteristics of a beam containing both the passive and active damping layers. It is shown that the combined system could be used effectively to dampen the structural vibration over a wide frequency range. Comparisons with only passive and only active damping schemes are also made. The influence and the mode dependence of control gain in a hybrid system is clearly brought out.

关键词： smart structure magnetostriction combined active and passive damping ferro-magnetic coating

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Plate vibration modes identification by using piezoelectric sensors

Plate vibration modes identification by using piezoelectric ...

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smart structures and materials 2000 Conference

作者： Song, JK Washington, G Ohio State Univ Intelligent Struct & Syst Lab Columbus OH 43210 USA

ISBN: (纸本)0819436038

In this paper, the authors present vibration mode identification of rectangular plates by using discrete piezoelectric materials. The novelty in this study stems from the fact that only spatial information is used. The analytical development and numerical simulation results of the method are also included. For the structural vibration control community, identification of the dominant vibration has been an important issue. If the dominant vibration modes are successfully identified, the control engineers can choose a proper control gain set which has been pre-tuned for the identified vibration mode. As the development of piezoelectric materials progressed, vibration mode identification techniques step into a new stage. Several papers reported vibration mode identification by using distributed piezoelectric modal sensors. Unfortunately, the spatially filtering methods need specially designed configuration corresponding to the geometry of the structures. These difficulties hinder the application and development of modal sensing and vibration control technology. In this paper, the authors develop a new method of the mode identification, and present analytical simulations for rectangular plates and circular plates. Finally, experimental verification of the method is also presented.

关键词： Sensors Vibration control Bessel functions Ferroelectric materials Francium Numerical simulations Protactinium Intelligence systems Intelligent sensor systems Intelligent sensors

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