JPH08279715A - Expandable body structure - Google Patents

Abstract

PURPOSE: To provide an expandable body structure which improves film surface accuracy without damaging housing property. CONSTITUTION: Elements 1a and 1b are thermal, optical or ultraviolet curing type inflatable films, the film 1a is provided for mirror and the film 1b is provided for a radome. An element 2 is a cable network, an element 3 is a hoop structure (outer ring), elements 4 are control mechanisms for controlling the lengths of respective cables 21, and elements 5 are fixtures for fixing the respective cables 21 onto the inflatable film 1a. The cable network 2 is constituted by joining the respective cables 21 and its nodes 22 are fixed onto the film 1a by the fixer 5. The cable at the terminal of the cable network 2 is fixed to the hoop structure 3. The inflatable films 1a and 1b are expanded by inert gas, etc., and cured by solar heat or ultraviolet radiation. The cable network 2 is arranged on a closed film surface and after the film surface is cured, a hard point (rigid node) 5 is provided. Thus, even after the internal pressure of gas is eliminated, structural stability is kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure deployed in space or on the ground, and more particularly to a large-scale structure (antenna, radar, etc.) that requires high accuracy.

[0002]

2. Description of the Related Art Spacecraft bodies such as artificial satellites, spacecraft, manned spacecraft, and space applications such as space antennas, solar sails, etc.
There is a great demand for improving reliability.

In particular, in missions requiring a large scale mechanism and high precision, many deploying mechanisms, joint devices, and adjusting mechanisms are mounted in order to deploy large-scale, highly accurate structures in space. Tends to conflict with ensuring reliability,
In-orbit defects related to deployment are sometimes fatal for missions in space utilization. Also,
In these mechanically deployed structures, the number of mechanisms, complexity, and clearance become strict as the mission, especially the structural scale and accuracy requirements expand, so the cost for designing and manufacturing increases, and deployment reliability is increased. The cost and time for tests and analyzes for compensation on the ground tend to increase dramatically.

Now, as the conventional deployable structure,
In addition, a "simple inflatable structure" in which one film surface is expanded like a balloon and used as an antenna for space, for example
Is known (see Japanese Patent Laid-Open No. 2-288704, FIG. 6 and FIG. 7). In this structure, when launching a satellite, one film surface is folded, gas is released inside the film surface in orbit, and the film surface is expanded like a balloon by a slight internal pressure against outer space vacuum. It is hardened by solar heat or ultraviolet rays, and can be easily stored in the satellite.

Secondly, there is a "modular type inflatable structure" in which the film surface is divided in order to improve the accuracy after curing, and the inflatable film surface which is divided into small parts is mounted on the frame of the truss structure (Japanese Patent Laid-Open No. 2-288704). (See FIGS. 4 and 5).

Thirdly, the structure accuracy of the film surface is obtained by pulling the film surface with a mesh or a large number of wires without applying internal pressure, and the whole structure is supported by a deployment truss "mesh +".
"Expanded truss structure" is known.

[0007]

According to the first "simple inflatable structure" described above, although the storage capacity in the satellite is good, the structural accuracy after curing depends on the internal pressure, so that the structural accuracy is difficult. There's a problem.

In the second "modular type inflatable structure", since the deployable truss is used, the structural accuracy after curing is improved, but there is a problem that the weight becomes heavy and the structure becomes complicated.

The third "mesh + deployment truss structure" is
It is not necessary to apply internal pressure to the membrane surface, but when a curved surface is formed, the orthogonal curvature of the surfaces becomes positive and negative and a smooth curved surface cannot be formed (so-called saddle type deformation), so a smooth curved surface is required. A lot of adjusting wires and deployable trusses are required to make them, resulting in a large number of parts and a heavy weight. As a result, there are many adjustment points, it is difficult to verify on the ground, the reliability of deployment decreases, and the manufacturing cost increases.

[0010]

In order to solve the above-mentioned problems, in the present invention, a closing film surface is formed of a thermosetting or ultraviolet-curing resin or composite material, and the closing film surface is formed with an inert gas or the like. In order to be cured by solar heat or ultraviolet rays, a cable network is provided in the surface of the closing membrane, and a plurality of rigid nodes are provided on the surface of the closing membrane after curing by the cable network.

[0011]

[Function] The closing film surface composed of a thermosetting or ultraviolet curable resin or a composite material is expanded with an inert gas,
Cure with solar heat or UV light. The cable network is located on the closed membrane surface and provides a hard point after hardening of the membrane surface. As a result, the position of the film surface does not change even if the internal pressure changes, and a highly accurate film surface is formed.
Further, since the film surface has rigidity of itself after hardening and the cable network in a tensioned state, structural stability is maintained even if the internal pressure of gas disappears.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1A and 1B are views showing an embodiment of a developed structure according to the present invention, FIG. 1A is a side view showing a part of a cable network, and FIG. 1B is a plan view showing an inflatable membrane removed.

In FIG. 1, 1a and 1b are heat or light / ultraviolet curing type inflatable films, 1a is for a mirror surface, 1b is for a radome, 2 is a cable network,
3 is a hoop structure (outer ring), 4 is an adjusting mechanism for adjusting the length of each cable, and 5 is a fixture for fixing each cable to the inflatable membrane 1a.

The inflatable film 1a has, for example, a Kapton film (protective layer) on the outer side, a composite material on the intermediate layer, and a metal layer on the mirror surface. Inflatable membrane 1b
However, it is the same as the inflatable film 1a except that there is no metal layer.

The cable network 2 is formed by knotting a plurality of cables 21, and the knot points 22 are fixed to the membrane 1a by the fixtures 5. The cable at the end of the cable network 2 is fixed to the hoop structure 3. In addition, as shown in FIG. 5, the adjusting mechanism 4 includes a bolt 41 having a thread formed on the outer periphery thereof, a nut 42 fixed to the center of the bolt 41, and an outer cylinder screwed to a threaded portion of the outer periphery of the bolt 41. It is composed of 43 and 43. The cable 21 is connected to both ends of the bolt 41, and the length of the cable can be adjusted by rotating the nut 42.
As a material of the cable network 2 and the adjusting mechanism 4, a material having a small thermal strain and a property of transmitting electromagnetic waves, such as aramid fiber or quartz wire, can be used.

When used as an antenna for space, the hoop structure 3 has a joint structure that can be folded at a joint 31 as shown in FIG. 1 (B).

The cable network 2 forms a statically-determining truss, the number of cables 21 is Nm, and the knot 22
Let Ng be the number of points and Nc be the fixed number of degrees of freedom of the boundary, the structure is a statically definite structure that satisfies Nm + Nc = 3Ng, and the fixed point between the table and the membrane (the position of the fixture 5) is the desired position on the three-dimensional coordinates. In order to arrange the cable, the fixed point between the table and the membrane can be measured with a three-dimensional measuring machine, and the adjustment amount [ΔL] _{Nm * 1} of the cable can be uniquely obtained by the following equation (1). The subscript “ _{Nm * 1} ” indicates that [ΔL] is an Nm × 1 matrix (the same applies to the following formula). [ΔL] _{Nm * 1} = [M] _{Nm * Nm} [dX] _{(3Ng-Nc) * 1} (1) where [ΔL] _{Nm * 1} = [ΔL ₁ ΔL ₂ ... ΔL _Nm ] ^T [dX] _{( 3Ng-Nc) * 1} = [dX ₁ dY ₁ dZ ₁ ...] ^T. [DX] _{(3Ng-Nc) * 1} represents the target position of the fixed point. [M] _{Nm * Nm} is a known matrix (constant matrix) determined by the cable length and the three-dimensional coordinates.

The amount of adjustment of the cable is obtained as described above, and the inflatable membrane is inflated on the ground by applying the internal pressure, and the fixing point (position of the fixture 5) is three-dimensionally adjusted by the adjusting mechanism 4.

What is important here is that the cable network 2 only makes discrete hard points in the film surface, and that a curved surface such as a smooth parabolic surface can be accurately approximated by an inflatable surface between them. Therefore,
The cable network with a small number of cables can dramatically improve the accuracy of the inflatable structure. At this time, the only condition for the cable network to form a static truss condition is that the membrane surface subjected to internal pressure pulls the cable to give tension to the cable.

With the above structure, it is possible to realize a developed structure having high film surface accuracy. Regarding the storability, the storability is excellent not only on the inflatable membrane surface, but also because the cable network is an assembly of cables, the storability is good. At the time of deployment, it has a tension due to the internal pressure in the closed membrane surface and has a structure equivalent to the truss structure. Therefore, it is possible to have a hard point (rigid node) on the membrane surface, the position of which does not change due to the internal pressure. Since the film surface has its own rigidity after curing and the cable network in a tensioned state, there is no problem in structural stability even if the internal pressure is eliminated.

That is, the advantage of the truss structure, that is, the provision of hard points on the film surface can be realized by the cable network. Since the cable network is an aggregate of cables when stored, there are no problems of the truss, such as a large number of members, a large number of mechanical joints, an increase in weight and storage volume, and an increase in cost.

In addition, in order to obtain structural accuracy such as "mesh structure + deployable truss", the mesh is pulled by thousands of cables to improve the structural accuracy of the mesh (the accuracy of approximation to the parabolic surface of the antenna). It is possible to realize the structural accuracy of the inflatable membrane surface with a far smaller number of cables (a cable of about 1/100 can be used to obtain the same accuracy) than the method of outputting.

FIG. 2 shows an example in which the expanded structure of FIG. 1 is made larger in size and the number of cables in the cable network is increased, and is mounted on a spacecraft (satellite or the like). In the figure, 1a is a heat or light / ultraviolet curing type inflatable film (for radome), 2 is a cable network, 3 is a hoop structure (outer ring), 4 is a spacecraft body,
Reference numeral 5 is a sub-reflecting mirror, and 6 is a power feeding unit.

Next, the effect of the present invention will be described with reference to an example in which the number of hard points is changed and analyzed. In FIG. 3, the cable network 25 is one when the cable network used for the antenna with an opening diameter of 10 m is divided into six equal parts, and here, the accuracy is compared using a part (1/6) of the cable network. did. In FIG. 3A, Q is the opening side, K is the mirror surface side, and T is the apex. FIG.
(A) is when there are no hard points as in the past,
(B), (C), and (D) are hard points 51, respectively.
Shows the case of sequentially adding.

In FIG. 4, the horizontal axis represents the internal pressure (p / N), the vertical axis represents the mirror surface accuracy (e / D), and the relationship between the two is shown for each of (A) to (D) in FIG. As is clear from FIG. 4, B, C, D, and
As the number of hard points increases, the mirror surface accuracy improves, and in the case of the solid line D (only 19 on the mirror surface of the antenna with an aperture diameter of 10 m).
In the case of providing hard points), the mirror surface accuracy of 1/7 can be realized as compared with the case of A having no hard points.
That is, the mirror surface accuracy (structural accuracy) can be significantly improved by adding a small amount of cable network.

Further, it is impossible to realize the same accuracy as that of the present invention by the conventional general "mesh method" considering saddle type deformation of the mesh. Even if the number of supporting points of the mesh is increased to improve the accuracy, the number of cable networks is required to be several hundred times that of the present invention. According to the present invention, it is possible to realize a highly accurate curved surface, for example, a parabolic surface, a spheroidal surface, or a rotating hyperboloid in the case of an antenna, with a minimum cable network.

FIG. 5 is a partially enlarged view of the second embodiment of the present invention. In this embodiment, the inflatable membrane has a double structure in order to eliminate the unevenness of the membrane surface due to the depression at the fixing point between the cable and the membrane surface on the membrane surface. By making the atmospheric pressure different when the film surface is cured, the accuracy of the inner film surface used as the antenna mirror surface can be improved.

In FIG. 5, 11 is an outer inflatable film and 12 is an inner inflatable film (antenna mirror surface).
Is. A cable 21 forming a cable network is fixed to the inner inflatable membrane 12 by a fixture 52. A part of the outer inflatable membrane 11 is
It is connected to the fixture 52 by a hanging wire 53.
5, the same components as those in FIG. 1 are designated by the same reference numerals.

With the above structure, the inner pressure P ₂ is applied to the surface of the inner inflatable membrane 12 and the inner pressure P ₁ is applied between the outer inflatable membrane 11 and the inner inflatable membrane 12. The respective relationships between the internal pressures P ₁ and P ₂ and the pressure P _{o in} outer space are as follows. P _o <P ₁ <P ₂ P ₁ -P _o >> P ₂ -P ₁ As a result, the outer inflatable membrane 11 swells outward due to the large pressure difference P ₁ -P _o , giving a large tension to the suspension wire 52. As a result, tension is applied to the cable network and a statically determined truss is formed. Film surface of the inner inflatable layer 12 (mirror surface), due very small pressure difference P ₂ -P ₁ than the pressure difference P ₁ -P _o, to form a smooth curved surface.

With the above arrangement, the concave portion of the inner inflatable membrane 12 at the fixing point (position of the fixture 7) can be made smaller than in the case of the single inflatable membrane, which is very smooth. An inner inflatable membrane surface can be formed. In this case, the outer inflatable membrane surface 11 intentionally has a large convex pressure P.
Changed by ₁ -P _o, a dummy film surface for increasing the tension in the cable network.

[0031]

According to the present invention, a deployable structure that is structurally simpler, more reliable, and lighter than the conventional mechanical deployable structure can be realized, and can be used for structures on the ground or in space. Further, since a plurality of hard points are formed inside the film surface without impairing the storability and without structural limitation, a highly accurate structure can be realized. Furthermore, if an adjustment mechanism is provided on the cable, the three-dimensional position of the hard point can be easily set and adjusted by design, so a structure with much higher accuracy than the conventional inflatable structure can be realized and Not only can it be used for high-precision deployable antennas for space and condenser mirror surfaces. Further, if the film is doubled, the film surface accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a developed structure according to the present invention.

FIG. 2 is a perspective view showing an antenna using the deployable structure of the present invention.

FIG. 3 is a diagram showing a cable network prepared for analyzing the effect of the present invention, showing that (A) has no hard points and (B), (C), and (D) increase in that order.

FIG. 4 is a diagram showing mirror surface accuracy for each of (A), (B), (C), and (D) in FIG.

FIG. 5 is a diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 1a Inflatable membrane (for mirror surface) 1b Inflatable membrane (for radome) 2 Cable network 3 Hoop structure 4 Adjustment mechanism 5 Fixture

Claims (3)

[Claims] 1. A closure film surface is formed of a thermosetting or UV-curable resin or composite material, and the closure film surface is expanded with an inert gas or the like so that it can be cured by solar heat or ultraviolet rays. A deployable structure characterized in that a cable network formed by connecting the above cables is installed in a closed membrane surface, and a plurality of rigid nodes are provided on the closed membrane surface after curing by the cable network. 2. The unfolding structure according to claim 1, wherein the cable includes an adjusting mechanism that adjusts an individual cable length. 3. The outer membrane of the closure membrane having the cable network installed is covered with an outer membrane, and the outer membrane and the closure membrane are connected by a suspending wire. The expanded structure according to claim 1, wherein the outer membrane is expanded by applying an internal pressure with an active gas or the like.