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Deployment Control of Spinning Space Webs and Membranes
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Future solar sail and solar power satellite missions require deployment of large and lightweight flexible structures in space. One option is to spin the assembly and use the centrifugal force for deployment, stiffening and stabilization. Some of the main advantages with spin deployment are that the significant forces are in the plane of rotation, a relatively simple control can be used and the tension in the membrane or web can be adjusted by the spin rate to meet the mission requirements. However, a successful deployment requires careful development of new control schemes. The deployment rate can be controlled by a torque, applied either to a satellite in the center or by thrusters in the corners, or by deployment rate control, obtained by tether, spool braking or folding properties.

Analytical models with only three degrees of freedom were here used to model the deployment of webs and membranes for various folding patterns and control schemes, with focus on space webs folded in star-like arms coiled around a center hub. The model was used to investigate control requirements and folding patterns and to obtain optimal control laws for centrifugal deployment. New control laws were derived from the optimal control results and previously presented control strategies. Analytical and finite element simulations indicate that the here developed control laws yield less oscillations, and most likely more robustness, than existing controls.

Rotation-free (RF) shell elements can be used to model inflation or centrifugal deployment of flexible memebrane structures by the finite element method. RF elements approximate the rotational degrees of freedom from the out-of-plane displacements of a patch of elements, and thus avoid common singularity problems for very thin shells. The performance of RF shell elements on unstructured grids is investigated in the last article of this thesis, and it is shown that a combination of existing RF elements performs well even for unstructured grids.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , x, 64 p.
Series
Trita-MEK, ISSN 0348-467X ; 2008:10
Keyword [en]
Flexible structures, space webs, membranes, solar sails, solar power systems, deployment control, optimal control, centrifugal force deployment, spin deployment, rotation-free, shell elements
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-9574OAI: oai:DiVA.org:kth-9574DiVA: diva2:126605
Public defence
2008-12-08, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100729Available from: 2008-11-21 Created: 2008-11-17 Last updated: 2010-07-29Bibliographically approved
List of papers
1. Design Considerations and Deployment Simulations of Spinning Space Webs
Open this publication in new window or tab >>Design Considerations and Deployment Simulations of Spinning Space Webs
2007 (English)In: 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structual Dynamics and Materials Conrerence: Waikiki, HI; 23 April 2007 through 26 April 2007, 2007, 1503-1512 p.Conference paper, Published paper (Refereed)
Abstract [en]

ESA Advanced Concepts Team (ACT) has proposed to construct large space antennas and solar power systems by deploying and stabilising a large web in space. The idea originates from the Japanese "Furoshiki Satellite". Since an overly complicated control system contributed to the partly chaotic deployment, ACT suggests to use centrifugal forces to deploy the space web. In this study the design and folding pattern of space webs are discussed. An analytical model and a finite element model used to describe the deployment, from the chosen folding, are presented. Free deployment of space webs is studied and a first control strategy that enables controlled and stable deployment is suggested.

Series
Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, ISSN 0273-4508
Keyword
Finite element method; Mathematical models; Receiving antennas; Satellites; Solar cells; Solar power systems; Space web; Spinning space webs
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9645 (URN)2-s2.0-34547497219 (Scopus ID)978-1-56347-892-5 (ISBN)
Note
QC 20100729Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-07-29Bibliographically approved
2. Deployment Control of Spinning Space Webs
Open this publication in new window or tab >>Deployment Control of Spinning Space Webs
2009 (English)In: Journal of Guidance Control and Dynamics, ISSN 0731-5090, Vol. 32, no 1, 40-50 p.Article in journal (Refereed) Published
Abstract [en]

Space webs are lightweight cable nets deployable in space to serve as platforms for very large structures. Deployment and stabilization of large space webs by spin have gained interest because the rotational inertia forces are in the plane of rotation and the spin rate that determines the magnitude of the web tension can be chosen to meet the mission requirements. Nevertheless, a robust control method is required for a successful spin deployment. The control law used for the deployment of the Znamya-2 membrane reflector, for which a feedback-controlled torque is applied to the center hub, was applied here to a quadratic space web folded in arms coiled around the hub. To analyze the deployment, an analytical three-degree-of-freedom model and a fully three-dimensional finite element model were developed. The simulations indicate that it is favorable to deploy the web in just one step. It is also suggested that the simple analytical model can be used to determine important mission requirements such as the torque, power, and energy required for different deployment times.

Keyword
Aerospace vehicles; Control theory; Marine biology; Neural networks; Robust control; Spin dynamics; Three dimensional; Analytical models; Control laws; Deployment controls; Large spaces; Large structures; Light weight cables; Membrane reflectors; Mission requirements; One steps; Robust control methods; Rotational inertias; Spin rates; Three-dimensional finite element models; Web tensions
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9646 (URN)10.2514/1.37468 (DOI)000262494900003 ()2-s2.0-60349101978 (Scopus ID)
Note
QC 20100729. Uppdaterad från accepted till published (20100729).Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-07-29Bibliographically approved
3. Optimal Deployment Control of Spinning Space Webs and Membranes
Open this publication in new window or tab >>Optimal Deployment Control of Spinning Space Webs and Membranes
2009 (English)In: Journal of Guidance Control and Dynamics, ISSN 0731-5090, Vol. 32, no 5, 1519-1530 p.Article in journal (Refereed) Published
Abstract [en]

Future solar sail and solar power satellite missions will consider using centrifugal forces for deployment and stabilization. Some of the main advantages with spin deployment are that the significant forces are in the plane of rotation, and a relatively simple control can be used and the tension in the membrane or web can be adjusted by the spin rate. Existing control strategies seem to either consume excessive energy or cause oscillations. In this study, control laws are derived from the solution to relevant optimal control problems and existing controls. The derived control laws are used in deployment simulations with both simple analytical three-degree-of-freedom models and a fully-three-dimensional finite element model. The results indicate that the derived control laws can be used to minimize the energy consumption and oscillations as for an optimal control, yet retain the simplicity of previous control laws.

Keyword
Centrifugal Forces; Control laws; Control strategies; Deployment simulation; Energy consumption; Excessive energy; Optimal control problem; Optimal controls; Optimal deployment; Solar power satellites; Solar sails; Spin rate; Three dimensional finite element model; Centrifugation; Optimization; Simulators; Solar energy; Solar equipment; Spin dynamics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9647 (URN)10.2514/1.42203 (DOI)000269939800011 ()2-s2.0-72149125839 (Scopus ID)
Note
QC 20100729. Uppdaterad från submitted till published (20100729).Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-07-29Bibliographically approved
4. A Comparison of Rotation-Free Triangular Shell Elements for Unstructured Meshes
Open this publication in new window or tab >>A Comparison of Rotation-Free Triangular Shell Elements for Unstructured Meshes
2007 (English)In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 196, no 49-52, 5001-5015 p.Article in journal (Refereed) Published
Abstract [en]

Many engineering applications require accurate and rapidly computed thin-shell elements. Rotation-free (RF) shell elements include the bending behaviour of thin shells without introducing any additional degrees of freedom compared to a membrane element. Instead, constant curvatures are approximated from the out-of-plane displacements of a patch of usually four triangular elements. A consequence of this is that the accuracy for irregular meshes has been unsatisfactory. The aim of this study is to find an RF shell element which is accurate also for unstructured meshes. The main difference between existing elements is whether they assume two-dimensional constant curvatures over the patch or use superposition of one-dimensional constant curvatures for the three pairs of triangles. The first assumption fulfils constant curvatures for a Kirchhoff plate exactly, whereas the second and most common assumption only approximates constant curvatures. The first assumption is significantly more resistant to element shape distortions, whereas the second assumption is slightly faster to compute and more appropriate on boundaries where one or more elements are missing or several neighbouring elements share a side. The combination is significantly more accurate for irregular meshes than other comparable RF elements for linear benchmark tests.

Keyword
shell element; rotation-free; constant curvatures; unstructured mesh
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-9648 (URN)10.1016/j.cma.2007.06.017 (DOI)000250494900014 ()2-s2.0-34548794751 (Scopus ID)
Note
QC 20100729Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2010-11-08Bibliographically approved

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