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Optimization of modular tensegrity structures for high stiffness and frequency separation requirements
KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0001-8064-5463
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-5819-4544
2016 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 80, 297-309 p.Article in journal (Refereed) PublishedText
Abstract [en]

Tensegrities are cable-strut assemblies which find their stiffness and self-equilibrium states from the integrity between tension and compression. Low stiffness and coinciding natural frequencies are known issues. Their stiffness can be regulated and improved by changing the level of pre-stress. In vibration health monitoring, the first natural frequency is used as an indicator of better stiffness, but coinciding natural frequencies will be an obstacle in measuring and analysing the correct resonance. In this paper, the above two issues have been considered for modular tensegrity structures. The finite element model used considers not only the axial vibration of the components, but also the transversal vibration where non-linear Euler-Bernoulli beam elements are used for simulations. A genetic algorithm is used to solve the optimization problem, with a multi-objective criterion combination. The optimum self-stress of the tensegrity structures can be chosen such that their lowest natural frequency is high, and separated from others. Two approaches are used to find the optimal self-stress vector: scaling from a base module or considering all modules at once. Both approaches give the same optimum solutions.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 80, 297-309 p.
Keyword [en]
Tensegrity, Self-stress, Frequency separation, Optimization, Vibration health monitoring
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-182844DOI: 10.1016/j.ijsolstr.2015.11.017ISI: 000368204500025ScopusID: 2-s2.0-84955750596OAI: oai:DiVA.org:kth-182844DiVA: diva2:906593
Note

QC 20160224

Available from: 2016-02-24 Created: 2016-02-23 Last updated: 2016-04-29Bibliographically approved
In thesis
1. Vibration-based Assessment of Tensegrity Structures
Open this publication in new window or tab >>Vibration-based Assessment of Tensegrity Structures
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vibration structural health monitoring (VHM) uses the vibration properties to evaluate many civil structures during the design steps, building steps and service life.The whole function, expressed by stiffness and frequencies of tensegrity structures are primarily related to the level of pre-stress. The present work investigates the possibilities to use this relation in designing, constructing and evaluating the tensegrity structures.One of the aims of the thesis was to improve the current models for resonance frequency simulation of tensegrities. This has been achieved by introducing the bending behaviour of all components, and by a one-way coupling between the axial force and the stiffness.The environmental temperature effects on vibration properties of tensegrity structures have been also  investigated. Changes in dynamic characteristics due to temperature variations were compared with the changes due to decreasing pre-tension in one of the cables. In general, it is shown that the change in structural frequencies coming from temperature changes could of several magnitude as those from damage.Coinciding natural frequencies and low stiffness are known issues of tensegrity structures. The former can be an obstacle in VHM, while the later normally limits their uses in real engineering applications. It has been shown that the optimum self-stress vector of tensegrity structures can be chosen such that their lowest natural frequency is high, and separated from others.The environmental temperature effects on vibration properties of tensegrity structures were revisited to find a solution such that the natural frequencies of the tensegrity structures are not strongly affected by the changes in the environmental temperature. An asymmetric self-stress vector can be chosen so that the criterion is fulfilled as well as possible. The level of pre-stress can also be regulated to achieve the solution. The last part of this thesis, services as a summary of the work.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 158 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2016:05
Keyword
Tensegrity, Pre-stress, Vibration, Health monitoring, Buckling, Temperature effect, Vibration health monitoring VHM, Optimization
National Category
Applied Mechanics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-185789 (URN)
Public defence
2016-05-17, F3, Lindstedtsvägen 26, Stockholm, 13:46 (English)
Opponent
Supervisors
Note

QC 20160429

Available from: 2016-04-29 Created: 2016-04-27 Last updated: 2016-05-09Bibliographically approved

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