On the control of flexible structures by applied thermal gradients

Edberg, Donald L.

doi:10.2514/6.1987-887

Cited by 6 publications

(5 citation statements)

References 4 publications

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“…The boundary surface F is decomposed into parts with different boundary conditions, cf., Eqs. (3)(4)(5)(6), and the local derivative forms of the boundary and initial conditions are substituted into Eq. (33).…”

Section: Mls Sensitivity Analysismentioning

confidence: 99%

Simultaneous material/load/shape variations of thermoelastic structures

Meriç

1990

AIAA Journal

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Simultaneous variations of material properties, load functions, and shape configurations of dynamic thermoelastic structures are considered. A continuous approach is adopted in order to find the total variation of a general performance criterion. The present analysis may find important physical applications in the simultaneous shape optimization and control of large space structures in time by applied thermal and/or mechanical loads. The adjoint variable method and the material derivative concept are used to find the sensitivity expressions, which are checked by a simple one-dimensional example problem. Nomenclature a = heat source decision parameter a k = material/load decision parameters B -body force in example problem b = body force decision parameter bi = body forces c = heat capacity c 0 = wave speed in example problem E = modulus of elasticity f,g,h = integrands of performance criterion H = boundary curvature / = general performance criterion 7 = augmented performance criterion k = thermal conductivity L = length of rod «/ = unit vector normal to boundary surface Q = distributed heat source q = normal boundary heat flux q* = adjoint normal boundary heat flux qi = heat-flow vector q* = adjoint heat-flow vector T = interval of time, [Q,t f ] t = time variable tf = final time tj = boundary tractions t* = adjoint boundary tractions u = x component of displacements u * = adjoint displacement in x direction Ui = displacements u* = adjoint displacements Vi = deformation velocity vector V n = normal component of K/ K M = component of V { normal to A and tangent to F w = dummy variable x = axial direction in rod Xj = Cartesian coordinates a = thermal diffusivity (3 = linear coefficient of thermal expansion 7 = material property given by F = boundary surfaces r0,r 9 ,r M ,r r = boundary segments <5 = variation symbol Subscripts = Kronecker delta = strain tensor = fundamental characteristic value, = ir/2L = temperature = reference temperature = adjoint temperature = Lame's constant = discontinuity surface line on F = Lame's constant = density = normal stress in x direction = adjoint normal stress in x direction = stress tensor = adjoint stress tensor = pseudotime variable (for shape variations) = general material/load decision variable = general integrals = physical domain derivative with respect to x f normal derivative : initial value Superscripts 0°= boundary value = local derivative = time derivative

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Section: Mls Sensitivity Analysismentioning

confidence: 99%

Simultaneous material/load/shape variations of thermoelastic structures

Meriç

1990

AIAA Journal

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“…[121], a thermal actuator when applied with a voltage acts as a heat pump producing a temperature gradient that induces a deflection in the beam. Results in Edberg [121] show that if the voltage is chosen properly it can significantly dampen the first i, vibrational mode of a cantilever beam.…”

Section: 12mentioning

confidence: 99%

Analysis and design of robust decentralized controllers for nonlinear systems

Schoenwald¹

1993

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This report has been reproduced directly from the best available copy. Available to DOE and DOE contractors from the Office of Scientific and T_chnical Information,P.O. Box 62, Oak Ridge, TN 37831; prices available i'rom(615) 576-8401, FTS 626-8401. Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield,VA 22161.This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or ae3umes any legal liability or responsibilityfor the accuracy, com-,_ pleteness, or usefulness of any information,apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation,or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do Pot necessarily state or reflect those of the United States Government or any agency thereof. J

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“…As soon as the shape distortion is deemed unacceptable, the nodal positions of the structure should be adjusted to correct it. The adjustment is often achieved by changing the length of the structural members [2,3].…”

Section: Introductionmentioning

confidence: 99%

Multi-objective shape control of prestressed structures with genetic algorithms

2008

Proceedings of the Institution of Mechanical Engineers, Part G:

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The shape of a prestressed structure is sensitive to external errors/stimuli due to its lightweight and high flexibility. When the shape distortion is deemed unacceptable, adjustment of the nodal positions is required. In this article, the shape control of a prestressed structure is modelled as a multi-objective optimization problem. A novel multi-objective genetic algorithm has been proposed to solve this problem. In the proposed algorithm, a niche technique consisting of a crowding check and a filter process is introduced to ensure the diversity of the population, and simultaneously, to accelerate the revolution process. On the basis of a ranking scheme of the individuals' degree of constraint violation, a problem-independent penalty method for constraint handling has been proposed. In addition, some well-developed techniques, such as fitness evaluation with a ranking procedure and termination judging with the distance to the idea point, are properly selected and used. The proposed algorithm performs well in seeking Pareto optimal sets for the shape control of prestressed structures, which is verified by two examples.

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On the control of flexible structures by applied thermal gradients

Cited by 6 publications

References 4 publications

Simultaneous material/load/shape variations of thermoelastic structures

Simultaneous material/load/shape variations of thermoelastic structures

Analysis and design of robust decentralized controllers for nonlinear systems

Multi-objective shape control of prestressed structures with genetic algorithms

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