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smart structures and materials 1999 Conference

作者： Balachandran, B Zhao, MX Univ Maryland Dept Mech Engn College Pk MD 20742 USA

ISBN: (纸本)0819431419

Nonlinear oscillations of a thin, isotropic panel bearing piezoceramic patches are-studied in this. work. The thin panel, which is clamped along all four edges, forms one of the boundaries of an enclosure. Rigid walls form the other boundaries of the enclosure. The piezoceramic patches are located symmetrically on the top and bottom surfaces of the flexible panel. Nonlinear relationship between the free strain experienced by a piezoceramic patch and the applied electric field is considered along with panel nonlinear elasticity to derive the equations of motion of the plate-enclosure system. It is shown that a voltage input into a piezoceramic actuator pair results in both parametric and external excitations to the panel. For harmonic excitations, the features of the nonlinear responses obtained in the simulations show good agreement with related experimental results. It is seen that for the cases considered, the actuator nonlinearities have a stronger influence on the response than the panel nonlinear elasticity.

关键词： nonlinear oscillations piezoceramic actuator acoustics control actuator nonlinearities

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Nonlinear control of PZT actuated trailing edge flaps

Nonlinear control of PZT actuated trailing edge flaps

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smart structures and materials 1999 Conference

作者： Kurdila, A Li, J Fulton, M Webb, G Univ Florida Dept Aerosp Engn Mech & Engn Sci Gainesville FL 32611 USA

ISBN: (纸本)0819431419

While PZT exhibits only mild nonlinear response at low voltage levels, it is well-known that the response can be profoundly nonlinear at high field strengths. Moreover, the use of mechanical linkages and structural design to amplify the stroke of PZT-based actuation likewise can couple with this material nonlinearity:to yield a structural level nonlinearity that is non-negligible. In this paper, we investigate such a nonlinear response in a PZT actuated trailing edge nap attached to a scaled helicopter rotor blade. While the example studied in this paper is quite specific, the methodology derived is generally applicable. We extend the recent results of [18,19] for the derivation of closed loop control for active material actuated devices. In this technique, a compensator derived hem an offline identification of a Krasnoselski-Pokrovski hysteresis operator is cascaded with the plant. We show that the methodology is well-posed for the class of problems under consideration;we derive closed loop stability and robustness conditions that can be associated with the prediction error in the identified hysteresis operator. We study the performance of our methodology in numerical examples and discuss relevant experimental results.

关键词： Actuators Ferroelectric materials Nonlinear control Complex systems control systems Aerodynamics Nonlinear response Feedback control Kinematics Performance modeling

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Robust, compact and inexpensive analog controllers for cabin noise control

Robust, compact and inexpensive analog controllers for cabin...

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smart structures and materials 1999 Conference

作者： Chang, W Ramanathan, K Varadan, VV Varadan, VK Penn State Univ Engn Elect & Acoust Mat Res Ctr University Pk PA 16802 USA

ISBN: (纸本)0819431419

Active Noise control has been an area of research interest in the recent decades with the goal of providing reduced noise levels in automobile and aircraft enclosures. Although digital controllers are adaptable and efficient, they lack the simplicity of analog controllers due to the requirement of a computer, D/A and A/D boards. Analog controllers on the other hand can be designed to be compact using current IC technology and hence are relatively very cheap. The following paper studies the application of an analog robust controller to abate the noise radiated into a non-reverberant wooden enclosure by a clamped aluminum plate. Since only the odd-odd modes radiate efficiently, a SISO robust analog controller was designed and built inexpensively for a piezoelectric actuator and accelerometer sensor placed at the center of the plate. A reduction of 17dB is observed when the panel is excited at its fundamental frequency, the dominant radiating mode. When the plate is excited with narrowband noise (40-316Hz), the controller reduces the noise levels in the enclosure by 9dB. The experimental results agree well with the controller simulation carried out using MATLAB

关键词： cabin noise control robust control analog controller

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Performance of active vibration control technology: the ACTEX flight experiments

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smart materials & structures 1999年第6期8卷 767-780页

作者： Nye, TW Manning, RA Qassim, K TRW Space & Elect Grp Syst Engn Redondo Beach CA 90278 USA TRW Space & Elect Grp Dynam & Test Engn Redondo Beach CA 90278 USA USAF Res Lab Vehicle Technol Branch Kirtland AFB NM 87117 USA

This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I(ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 degrees C to 129 OC. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed spa

关键词： Intelligent structures

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Modelling stresses in piezoelectric smart structures under combined thermal and mechanical excitations

Modelling stresses in piezoelectric smart structures under c...

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Proceedings of the 1999 smart structures and materials - mathematics and control in smart structures

作者： Koko, Tamunoiyala S. Smith, Malcolm J. Orisamolu, Irewole R. Martec Ltd Halifax NS Canada

In this paper, the integrated finite element methodology developed in our earlier work for designing active vibration control strategies in smart structures, is extended to compute the stresses and strains in the structure, due to combined thermal, mechanical and electrical excitations. A layered composite brick elements with linear strain-displacement and linear thermopiezoelectric constitutive relations is used to model the structure. The method, which has been encoded into a software called smartCOM provides a design and analysis capability that simultaneously accounts for the coupled thermopiezoelectric and control capabilities of the smart structural systems. Numerical examples are provided for structures with surface bonded piezoelectric sensors and actuators, under various types of mechanical, thermal and electrical load. Comparisons are made to other available solutions to verify the accuracy of the smartCOM simulations. The method provides accurate results and is seen as a valuable tool for the design and analysis of these smart structures.

关键词： Intelligent structures

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Wavelets transform for boundary control of smart thin - Walled beam cantilever

Wavelets transform for boundary control of smart thin - Wall...

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smart structures and materials 1999 Conference

作者： Poterasu, VF Tech Univ Iasi RO-6600 Iasi Romania

ISBN: (纸本)0819431419

Wavelets provide a new tool in vibration, identification and control. By their properties wavelets transform are stronger than FEM and FFT. We dispose to several wavelets family as Haar, Daubechies, Morlet, Mallat, etc. and use the filter banks for vibration analysis. This paper deals with the problem of controlling the bending oscillations of a thin walled cantilever beam with arbitrary cross section. The control is achieved via the action of a bending moment applied at a tip of structure. A-possibility to generate the control bending moment at the wing tip is via the implementation into the structure of piezoactuators. The velocity feedback control allows the possibility to generate damping through the feedback gain coefficient. Feedback law where the bending moment at a tip is proportional to the velocity is included into matrix wavelet implementation. Numerical examples for PDE are computed and compared with other examples for particular cases included in earlier paper of Librescu, Na. The paper uses the Haar wavelet transform to algebrize PDE leading to a powerful and general method to study the nonlinear problems with more flexibility and localization of peak resonance in comparison with other procedures.

关键词： smart thin walled beam wavelet transform boundary control

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Roll maneuvering of flexible aircraft with distributed-parameter actuation via modal synthesis

Roll maneuvering of flexible aircraft with distributed-param...

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smart structures and materials 1999 Conference

作者： Öz, H Khot, NS Ohio State Univ Columbus OH 43210 USA

ISBN: (纸本)0819431419

The focus is on obtaining and identifying optimal distributed-parameter-control equivalent actuation profiles for desired roll maneuvers by a modal synthesis approach. The solution for distributed-parameter-control of an aeroelastic system is developed by synthesis of modal-state-space controllers designed via the globally power optimal Independent Modal-Space control (IMSC) technique. The desired maneuver(set-point) control performance is achieved by a modal-performance-output synthesis (MPOS) approach. The MPOS approach requires that each independent modal controller be allocated a desired portion of the total desired output performance. In view of this, a modal performance-output allocation optimization problem is also defined, which minimizes a hybrid measure of control power and elastic strain energy of the structure during aeroelastic control. Insight to distributed-parameter-control equivalent actuation solutions are sought by considering the aeroservoelastic interactions among vehicle motion, aerodynamics, structural flexibility and control actuators from the perspective of work-energy, control power, and control loading requirements. The modal synthesis approach is illustrated fora Eight vehicle wing design to achieve a 90 deg/sec roll-rate in a Mach 2 flight condition at altitude (20000 ft) via distributed-parameter equivalent actuation. The preliminary results indicate that such a roll-rate maneuver can be accomplished via distributed-parameter actuation with feasible levels of control power, work-energy, and control loadings through eliciting favorable aeroservoelastic interactions.

关键词： aeroelasticity aeroservoelasticity IMSC modal control distributed-parameter-control control power wing shaping distributed-parameter actuation non-self-adjoint system control

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Non linear motion and force control of shape memory alloys actuators

Non linear motion and force control of shape memory alloys a...

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smart structures and materials 1999 Conference

作者： Benzaoui, H Chaillet, N Lexcellent, C Bourjault, A Lab Automat Besancon LAB UMR CNRS 6596 F-25000 Besancon France

ISBN: (纸本)0819431419

Among the numerous studies published in the field of shape memory alloys (SMA), an important part is devoted to the thermomechanical properties of these materials. Few studies have been done in order to develop control laws of SMA actuators for temperature, position and force control with guaranteed stability and performances. The reason is that these materials have an highly non linear dynamic behavior (including hysteresis) because of the physical principle of motions which is a solid-solid phase transition (between an austenitic and a martensitic phase). It is then difficult to guaranty stable control and to predict the dynamic behavior in closed-loop (trajectory and effort). For this purpose, this paper is focused on control of such actuators. To obtain a control law for the closed-loop motion or force control, we use a non linear dynamic model performed in a previous work. With this dynamic model, we use non linear control techniques based on the Lie algebra to obtain the control laws for the position or the force closed-loop. Experimentation show that the proposed method is very useful for the control of SMA actuators.

关键词： SMA actuators thermomechanical modeling motion control force control

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Shaping of distributed piezoelectric sensors for flexural vibrations of smart beams

Shaping of distributed piezoelectric sensors for flexural vi...

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smart structures and materials 1999 Conference

作者： Irschik, H Krommer, M Pichler, U Johannes Kepler Univ Inst Mech & Mech Engn Div Tech Mech A-4040 Linz Austria

ISBN: (纸本)0819431419

This paper is concerned with flexural vibrations of smart beams. Layers made of piezoelectric material are used to perform a distributed sensing of strains. In the present contribution, special emphasis is given to the sensor shaping problem, which can be stated as follows: Seek a shape function of the distributed sensor such that a mechanical interpretation of the sensor output is possible, e.g. to interpret the output as deflection, or as a slope. The scope of the present contribution is to find a class of easy to obtain analytic solutions of this inverse problem, and to present an experimental verification. Within the context of the Bernoulli-Euler beam theory, sensor equations are derived taking into account the coupling of mechanical and electrical fields. The principle of virtual work is then applied to derive integral equations for the structural deformations e.g. deflection, slope, curvature. Comparing these integral equations, the above sensor shaping problem is solved. Beams with different boundary conditions are considered. Furthermore, shape functions responsible for non-uniqueness of the shaping problem are derived. These nilpotent solutions may be added to the above derived solution of the sensor shaping problem without influencing the measured sensor signal. The analytical results of the sensor shaping problem are realized in a series of experiments for a cantilever beam, without and including a redundant support. Deflections measured by the new type of distributed piezoelectric sensor are compared to laser based distance measurements. Excellent coincidence between these measurements is found.

关键词： flexural vibrations smart beams piezoelectric sensors sensor shaping problem nilpotent solutions

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Peak to peak control of an adaptive tensegrity space telescope

Peak to peak control of an adaptive tensegrity space telesco...

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smart structures and materials 1999 Conference

作者： Sultan, C Corless, M Skelton, RE Purdue Univ Sch Aeronaut & Astronaut W Lafayette IN 47907 USA

ISBN: (纸本)0819431419

This paper proposes a new space telescope design in which the classical truss structure of the telescope is replaced by a tensegrity structure. A tensegrity structure is a prestressed structure whose structural shape is guaranteed by the interaction between elastic members in tension (tendons) and a set of rigid members (bars). A nonlinear dynamical model of a two stage tensegrity telescope is derived. Static analysis is performed for tensegrity telescopes composed of two stages. The performance specifications for the control system are formulated in terms of the peak lvalue (L-infinity norm) of the pointing and alignment errors. The control system is designed to minimize a certain upper bound on this peak value subject to a peak value constraint on the external disturbances. Evaluations of the design are performed through numerical simulations of the closed loop system.

关键词： Mirrors Space telescopes Telescopes control systems control systems design Optical instrument design Space mirrors Adaptive control Device simulation Mathematical modeling

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