Ayako Torisaka

Simultaneous optimization of thickness and sticking position of multilayer damping materials for vibration control of small satellite

Layered structures making use of viscoelastic materials are very effective especially for the passive vibration control of small satellite because of its lightweight and easiness to handle. But, even the masses of damping elements are not ignorable and which causes the change of vibrational characteristics. Vibration control of solar panel is important because the fracture of solar cell turn to be fatal for the mission of the small satellite. Therefore, an effective way of passive damping may play a big role on controlling the overall response of small satellite in wide frequency domain and the specific response which causes fracture. This research first examines the frequency responses of certain points of solar panel by evaluating the influence of pasting positions of damping elements and of thicknesses of viscoelastic and constraining layers. Then the thickness of each layer and the pasting points of damping elements are taken as design variables, and optimum values are found respectively by using Multi Objective Genetic Algorism (MOGA). The optimum model obtained by the optimization of pasting points is more effective in comparison with one by the thickness optimization because the ratio of strain energy absorbed by viscoelastic layer turn out to be higher than that absorbed by constraining layer at lower frequency domain. Finally the thicknesses and pasting points are optimized simultaneously whose results attain the most effective vibrational characteristics through overall the frequency domain (02500Hz). The percentage of strain energy absorbed by viscoelastic layer is increased considerably. In consequence, simultaneous optimization of layers and pasting position can give very effective means for design decision of the high damping performance through wide range of frequency domain.

Optimum design of launch vehicle adapters for small satellites

Small satellites are often subjected to severe vibrational load and acoustic impulse by launchers. However, large structural modifications or equipment of control system are not usually used because of sizes of structures, constraints of weight and costs. As simple and effective ways, adding stiffeners and damping materials are sometime used. Alternative way is to isolate small satellite directly from vibrational loads transmitted from the main rocket body. In other words, such launch vehicle adapters (LVA) should be so desired that may transmit the vibrational load little to the satellites. The number of launches of small satellites will be expected to increase lately where some kinds of small satellites may be installed at a time by using one platform. Therefore, LVAs are desired to design optimally that have less sensitivity of the response to the vibration input, the number and the specifications of different small satellites. So in this study before considering topology and shape optimization design of LVAs, attention is paid to the position of small satellite on the LVA tables, layout of small satellites which can be used robustly for a variety of small satellites.

Reduction of Dynamic Responses of Small Demonstration Satellite by Optimizing the Pasting Regions of Multilayered Viscoelastic Materials

Small satellites are often subjected to severe vibrational loads and acoustic impulses by launchers. However, large structural modifications or additions of equipments of control systems are not usually made use because of sizes of structures, weight, costs, and limitation of available region of control devices. One of the effective ways to prevent small satellites from the damages by severe vibrational and acoustic loads lies in adding multilayered viscoelastic damping materials to the structures and/or reinforcing structures by stiffeners. Viscoelasric materials with constraining layer are sometimes used for damping element in the field of cars. Effectiveness of applying damping layered materials to such light weight structures as solar panels of small satellites were studied by the authors in the previous work. Then the objective of this research is to reduce the overall frequency responses of Small Demonstrate Satellite (named SDS-1) under plan through the prescribed frequency domain by optimizing the applying regions of viscoelastic materials using Multi Objective Genetic Algorism (MOGA). The numerical results are compared with the experimental results and discussed from the many engineering points of view.

Membrane space structure with sterical support of booms and cables

Authors suggested a new structure combined with lightweight membranes and booms using convex tape considering its application as a space structure. . The larger membrane is preferred to get a solar effect from sails and power generation needs. In the past researches, we assumed a square shaped flat structure and studied the use of cables, positions of cables connecting between boom and membrane. In this paper, an additional studies about a steric membrane structure with booms and cables has been carried out to confirm a structural properties. We manufactured experiment model for verifying these properties, and also we confirmed about the same kinds of properties of hexagonal structure.

Vibration Reduction of Launch Vehicle Adapter Table in Wide Frequency Domain and Investigation of Install Configuration for Small Satellites

This research presents the vibration control by supporting structure, mainly by the Launch Vehicle Adapter (LVA), and shows the effectiveness of generalized LVA on which different kinds of small satellites can be installed and having robustness to vibration responses. Here, LVA table with three kinds of small satellites is of interest, and optimization of install position of each satellite is carried out to focus on the parameters which are generally different from launch by launch. Then it became obvious that the mass variety is critical to the vibration characteristics than change of numbers of installed satellites. Then, topology optimization of LVA is done by using the proposed formulation for vibration control uniformly throughout wide frequency domain. Compared with the conventional way as using minimization of compliance, the structural topologies by proposed formulation enable us to have stable reduction of responses that are not attained by the conventional way. And the design by proposed method also has robustness to mass variation. So the basic guidelines of design how to install satellites can be obtained by proposed method at the initial design phase in view of vibration control