Yasuyuki Miyazaki

Concept of the tension truss antenna

The concept of the tension truss antenna is proposed. It is shown that a parabolic reflector surface can be formed by a three-dimensional integrated cable lattice system that can be called a tension truss. The tension truss antenna consists of a triangular-faceted cable truss, the rf reflector surface, and a supporting structure which provides support as well as pretension of the cable lattice. The primary feature of the antenna is that its shape is virtually determined by geometric quantities such as the lengths and arrangement of cable members. Because of this feature, the adjustment of antenna surface can be done directly by changing lengths of cable members which form the surface

Mission Report on The Solar Power Sail Deployment Demonstration of IKAROS

Hirokata Sawada Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Osamu Mori 2 Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Nobukatsu Okuizumi Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Yoji Shirasawa University of Tokyo, Tokyo, JAPAN Yasuyuki Miyazaki Nihon University, Chiba, 274-8501, JAPAN Michihiro Natori Waseda University, Tokyo, 169-8555, JAPAN Saburo Matunaga Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiroshi Furuya Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiraku Sakamoto Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN

Dynamic Wrinkle Reduction Strategies for Cable Suspended Membrane Structures

The present study addresses vibration mitigation of membrane structures the boundaries of which are surrounded by weblike perimeter cables. This proposed membrane design realizes significant structural mass reduction when compared to the conventional catenary design. A key dynamic characteristic of the proposed structure is that support perturbations propagated into the outer perimeter cables have a minor effect on the vibration frequencies of the membrane. This property has been exploited in the development of vibration mitigation strategies using active control. This is corroborated by carrying out nonlinear transient analysis, which accounts for the effect of wrinkles in the membrane. The results confirm that disturbances emanating from the support structures can be isolated by the outer perimeter cables while maintaining the interior membrane in a wrinkle-free taut condition. A simple active control law has been developed and applied to only the outer perimeter cables. Numerical simulations show that the combination of the web-cable girded membranes and the proposed vibration mitigation strategy can provide sufficient damping for both in-plane and out-of-plane vibrations.

DEPLOYMENT DYNAMICS OF INFLATABLE TUBE

There has been a lot of attention recently on space inflatable membrane structures, because they have the excellent characteristics such as lightweight, simple deployment mechanisms, and high packaging efficiency, and also because the manufacturing technology has progressed. Some programs taking the advantages of inflatable structures have been suggested already. Researches on material, strength and shape accuracy after deployment have been progressing fairly. However, deployment dynamics of inflatable structures has not been researched adequately. This paper shows a numerical method of analyzing the deployment motion of inflatable membrane structures. The presented method is based on finite element procedure taking into account the interaction of the deformation of the membrane and the pressure of the inflation gas. It adopts a conservation algorithm of energy and momentum to stabilize the numerical time integration. Numerical examples and the corresponding experimental results are presented. They have good agreements with each other, which shows the validity of the proposed numerical method.

Analytical solution of spatial elastica and its application to kinking problem

Abstract An analytical solution is presented for the spatially large deformation of a thin elastic rod (spatial elastica) which is naturally straight and uniform with equal principal stiffnesses and is subjected to terminal loads. The elastica can suffer not only flexure and torsion as in the classical Kirchhoff theory, but also extension and shear. The present solution is expressed in integral form and described in terms of only four parameters. This solution clears the difficulty with the polar singularity in the use of Euler angles. Hence, the numerical analysis is possible for various boundary value problems with no limitation. In this paper we study the post-buckling behavior of an elastica under the terminal twist and uniaxial end-shortening, and give a theoretical explanation to commonly observed phenomena such as secondary bifurcation, formation of a kink, snap-through behavior. The contact problem is analyzed in the case where the elastica contacts with itself and forms a kink. These results are available for other analysis, e.g., based on finite element approximations.

Analysis of Membrane Dynamics using Multi-Particle Model for Solar Sail Demonstrator "IKAROS"

1 Post-doctoral Researcher, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 2 Assistant Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 3 Professor, Department of Aerospace Engineering, 7-24-1 Narashinodai, Funabashi, Chiba, Japan. 4 Assistant Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 5 Graduate Student, Department of Aeronautics and Astronautics, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, Japan. 6 Assistant Professor, Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 7 Post-doctoral Fellow, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 8 Associate Professor, Department of Built Environment, 4259-G3-6, Nagatsuta, Midori-ku, Yokohama, Japan. 9 Associate Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 10 Visiting Professor, Faculty of Science and Engineering, 55S-608, 3-4-1 Okubo, Shinjyuku, Tokyo, Japan. 11 Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 19th 4 7 April 2011, Denver, Colorado AIAA 2011-1890

Finite Element Modeling of Sail Deformation Under Solar Radiation Pressure

Anumerical structural model of a thin-film sail that simulates the deformation caused by solar-radiation pressure is developed, using a geometrically nonlinear finite element method (FEM). By using the finite element presented in this study, the force and moment exerted on an arbitrarily shaped solar sail subjected to solar pressure can be calculated accurately. In addition, it is shown that the sail deformation due to a solar-pressure load can be approximated by the deformation caused by the corresponding uniform gas-pressure load. This finding will significantly simplify analyses to improve attitude controller design as well as structural design of sailcraft, because commercially available FEM software can be used for the analyses.

Transient Dynamic Analysis of Gossamer-Appendage Deployment Using Nonlinear Finite Element Method

The present study develops a new three-dimensional Timoshenko beam finite element (FE) whose length can be varied during transient dynamic analyses. The variable-length element enables the dynamic deployment analysis of flexible appendages with non-negligible bending stiness. In addition, the developed scheme employs an implicit time integration whereby energy and momentum in the system is properly conserved, and no artificial numerical dissipation is introduced. As a result, the scheme makes it possible to evaluate the impact of structural damping on the system’s dynamics. The developed beam element is then used in an FE model of a solar sailcraft currently developed in Japan, and its deployment dynamics is analyzed allowing for the non-zero bending stiness of the bundled membranes, as well as the eect of some realistic design imperfections.

Distributed and Localized Active Vibration Isolation in Membrane Structures

Once a membrane starts vibrating, suppressing the vibration is very difficult. Thus, the present study primarily aims at isolating a membrane from major disturbance sources, that is, from support structures. The present study introduces weblike suspension cables around a membrane and develops in theory a vibration-isolation strategy applied only along the cables. First, collocated small actuators/sensors are attached at the interfaces of the cables and the membrane to realize a distributed cable-tension control. Second, linear theory-based localized controllers are designed for suspension-cable substructural models. The feedback laws for these two kinds of controllers are derived employing a partitioned equation of motion. The resultant control system is lightweight, simple, low order, robust, and redundant A series of transient analyses using a geometrically nonlinear finite-element method corroborates the effectiveness of the proposed vibration-isolation strategy.

Deflection of multicellular inflatable tubes for redundant space structures

A new concept of redundant space structures using multicellular inflatable elements is proposed, and the results of basic analyses on simple multicellular models are reported. Much effort has been devoted to methods for sufficiently hardening the inflatable elements in space to tolerate damage sustained from space debris, especially with respect to rigidization of a membrane; however, if the structures are redundant, they do not need to be as stiff and strong as those without redundancy. Deflections of two kinds of multicellular cantilever inflatable tubes are numerically investigated. First, nonrigidized tubes are analyzed by the modified Euler-Bernoulli beam theory. Second, rigidized tubes with slackening effects of the membrane are simulated using the modified nonlinear finite element method. The results show that multicellular tubes can be redundant against problems with pressurization and can be as stiff and as strong as monocellular models with less internal gas. In the multicellular rigidized inflatable tubes, maintaining a small amount of internal pressure is quite effective to prevent the deformation of the cross section, which causes a drop in stiffness and strength. Therefore, adopting a redundant system is effective both for rigidized and nonrigidized inflatable elements.