CN117855801A - Annular-radial rib type expandable antenna structure - Google Patents

Abstract

The present invention discloses an annular-radial rib-type deployable antenna structure, including an annular truss structure located outside and a tri-fold rib structure located inside, one end of the tri-fold rib structure is connected to the annular truss structure, and the other end is connected to a base located at the center of the entire antenna structure; the annular truss structure is composed of a plurality of transverse quadrilateral units connected, and the tri-fold rib structure is composed of a first section rib, a middle section rib, and a final section rib connected in sequence; a mesh parabolic metal wire mesh is connected from the bottom end of the external annular truss structure to the base, which forms a back-to-back structure with the tri-fold rib structure, and each metal wire is connected to the tri-fold rib surface cable net through a plurality of vertical adjustment cables. The antenna structure of the present invention combines an annular truss antenna with a radial rib antenna, and has the advantages of a large expansion-contraction ratio and high rigidity of an annular truss antenna, as well as the advantages of high precision of a rib antenna.

Description

Annular-radial rib deployable antenna structure

Technical Field

The present invention belongs to the technical field of satellite-borne annular deployable antennas, and in particular relates to an annular-radial rib type deployable antenna structure.

Background technique

Satellite-borne deployable antennas are mainly used in space communications, earth observation, meteorological monitoring and other fields. With the development of space technology, in order to meet larger and more complex space missions, satellite-borne antennas need to have higher precision, rigidity, larger working aperture and lighter mass. Since the antenna needs to be placed in the limited fairing space, the overall height and volume of the antenna mechanism are limited. Therefore, large-aperture satellite antennas must be deployable mechanisms and have a high deployment ratio. They are usually placed in the rocket's fairing in a folded state, and are deployed after the launch vehicle reaches the designated working orbit to reach the predetermined posture for operation. Compared with fixed-surface antennas, inflatable antennas and other types of antennas, cable-net reflector antennas have many advantages such as smaller mass and larger deployment ratio, and have become the preferred choice for larger-aperture antennas in various countries.

At present, cable net reflector antennas can be roughly divided into umbrella antennas, frame antennas, and ring truss antennas. Umbrella antennas have high precision, but because they contain multiple ribs, their rigidity is poor. Ring truss antennas have the characteristics of large aspect ratio, which is very advantageous when the antenna diameter is large, but their precision is not as good as umbrella antennas. Therefore, it is very important to improve the antenna precision, aspect ratio and rigidity at the same time.

Summary of the invention

The object of the present invention is to provide a circular-radial rib type deployable antenna structure, which combines a circular truss antenna and a radial rib antenna, and has the advantages of a large expansion/contraction ratio and high rigidity of a circular truss antenna, as well as the advantage of high precision of a rib antenna.

The technical solution adopted by the present invention is that the annular-radial rib type expandable antenna structure includes an annular truss structure located on the outside and a three-fold rib structure located on the inside, one end of the three-fold rib structure is connected to the annular truss structure, and the other end is connected to a base located at the center of the entire antenna structure; the annular truss structure is composed of a plurality of transverse quadrilateral units connected, and the three-fold rib structure is composed of a first section rib, a middle section rib, and a last section rib connected in sequence; a mesh parabolic metal wire mesh is connected from the bottom end of the external annular truss structure to the base, which forms a back-to-back structure with the three-fold rib structure, and each metal wire is connected to the three-fold rib surface cable net through a plurality of vertical adjustment cables.

The present invention is also characterized in that:

The transverse quadrilateral unit includes two radial quadrilateral units located on two opposite sides thereof, the two radial quadrilateral units have the same structure but are inverted upside down, and the two radial quadrilateral units are connected by a first cross bar and a second cross bar; two adjacent transverse quadrilateral units are connected by two third cross bars, and the two ends of the third cross bar are respectively connected to the radial quadrilateral units in the two adjacent transverse quadrilateral units.

The radial quadrilateral unit includes an inner vertical rod and an outer vertical rod. The inner vertical rod and the outer vertical rod have the same length and are arranged in parallel. A hingeless base and a hinged base are respectively arranged at the two ends of the inner vertical rod and the outer vertical rod. The hingeless base and the hinged base fix the inner vertical rod and the outer vertical rod. The slider is sleeved on the inner vertical rod and the outer vertical rod and can slide up and down along the inner vertical rod and the outer vertical rod.

Both ends of the crossbar are provided with pipe joints, and the pipe joints at both ends are respectively hinged to the hinged base and the sliding block in two adjacent radial quadrilateral units through hinge connection mechanisms.

The slider, the hinge connection part including the hinge base and the pipe joint are all provided with two holes; the hinge connection mechanism includes a pulley, bearings are provided on both sides of the pulley, the pulley and the two bearings are all arranged on the inner side of the hinge connection part, and washers and bushings are sequentially provided on the outer side thereof, and the pin a passes through all the parts and holes and is connected with the nut a.

Two adjacent radial quadrilateral units are connected with two steel wire ropes, which cross each other and have two ends respectively connected with a hinged base and a slider at a diagonal position.

The first section rib, the middle section rib and the last section rib are connected in sequence through the inter-rib locking and connecting mechanism; the first section rib is connected to the transverse quadrilateral unit of the external annular truss through the rib connector and the inter-rib locking and connecting mechanism, wherein the rib connector is connected to the transverse quadrilateral unit and then connected to the first section rib through the inter-rib locking and connecting mechanism; the last section rib of the three-fold rib structure is connected to the base through the end rib connecting mechanism.

The locking and connecting mechanism between the ribs includes two connecting blocks a arranged on both sides of a part to be connected and two connecting blocks b arranged above another part to be connected, the connecting block b is located on the inner side of the connecting block a, and connecting blocks a and b are both provided with connecting holes, and the four connecting holes are coaxial, and the pin shaft b passes through the four connecting holes and is connected and fixed with the nut b; a positioning hole is provided on the connecting block a, and a mounting hole is provided on the connecting block b, the positioning hole is a countersunk hole, and the mounting hole is a through hole, a positioning pin shaft is provided in the mounting hole, and a spring is provided between the two positioning pin shafts; when the antenna is in an unfolded state, the positioning hole and the mounting hole are not coaxial, and the spring is in a compressed state; when the three-fold rib structure is unfolded to a predetermined position, the positioning hole and the mounting hole are coaxial, and the spring releases elastic potential energy to push the two positioning pin shafts into the positioning holes on both sides respectively to achieve locking.

The terminal rib connection mechanism comprises a terminal rib connection member and a rib base. The terminal rib connection member is fixedly connected to the terminal rib, the rib base is fixed on the base of the antenna, and the terminal rib connection member is hinged to the rib base through a pin shaft c and a nut c.

The antenna structure is driven by ropes. There are two driving ropes, which are respectively connected in series with the upper and lower parts of the external ring truss structure. The driving rope enters the first cross bar or the second cross bar through the slider, and after coming out of the first cross bar or the second cross bar, it bypasses the hinged base and enters the third cross bar. In this way, it circulates and connects the upper or lower part of the external ring truss structure in series.

The beneficial effects of the present invention are:

The antenna structure of the present invention uses a single-ring deployable truss as the external structure and a three-fold rib structure as the internal structure, which can effectively improve the low rigidity of the rib structure, while also enabling the antenna structure to obtain better accuracy, and the antenna structure has a higher folding ratio and can be stored in a limited storage space. In addition, the external structure of the antenna of the present invention uses an oblique steel wire rope to connect two adjacent radial quadrilateral units, which increases the stability of the structure and reduces the overall mass of the deployable antenna truss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the unfolded structure of the antenna structure of the present invention;

FIG2 is a schematic diagram of the unfolded structure of a certain transverse quadrilateral unit combined with an internal rib structure in the antenna structure of the present invention;

FIG3 is a schematic diagram of the unfolded structure of the transverse quadrilateral unit in the antenna structure of the present invention;

FIG4 is a schematic structural diagram of a hinge connection mechanism in the antenna structure of the present invention;

FIG5 is a schematic diagram of the structure of the locking and connecting mechanism between ribs in the antenna structure of the present invention;

FIG6 is a schematic structural diagram of the terminal rib connection mechanism in the antenna structure of the present invention;

FIG. 7 is a schematic diagram showing the connection and driving method of the driving cable in the antenna structure of the present invention.

In the figure, 1. end rib connection mechanism, 11. end rib connection piece, 12. rib base, 13. screw, 14. pin c, 15. nut c, 2. base, 3. transverse quadrilateral unit, 31. radial quadrilateral unit, 311. inner vertical rod, 312. outer vertical rod, 313. base without hinge, 314. base with hinge, 315. slider, 32. first cross bar, 33. pipe joint, 34. hinge connection mechanism, 341. pulley, 342. bearing, 343. washer, 344. 4. Bushing, 345. Pin a, 346. Nut a, 35. Third cross bar, 36. Second cross bar, 37. Rib connector, 38. Wire rope, 4. First section rib, 5. Locking and connecting mechanism between ribs, 51. Connecting block a, 52. Connecting block b, 53. Connecting hole, 54. Pin b, 55. Nut b, 56. Positioning hole, 57. Mounting hole, 58. Positioning pin, 59. Spring, 6. Middle section rib, 7. Last section rib, 8. Wire mesh, 81. Adjusting cable, 9. Driving cable.

Detailed ways

The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

The annular-radial rib type expandable antenna structure of the present invention has a structure as shown in Figures 1 and 2, including an annular truss structure located on the outside and a three-fold rib structure located on the inside, one end of the three-fold rib structure is connected to the annular truss structure, and the other end is connected to a base 2 located at the center of the entire antenna structure; the annular truss structure is composed of a plurality of transverse quadrilateral units 3 connected together, and the three-fold rib structure is composed of a first section rib 4, a middle section rib 6, and a last section rib 7 connected in sequence; a mesh parabolic metal wire mesh 8 is connected from the bottom end of the external annular truss structure to the base 2, which forms a back-to-back structure with the three-fold rib structure, and each metal wire is connected to the three-fold rib surface cable net through a plurality of vertical adjustment cables 81.

Example 2

On the basis of Example 1, as shown in Figure 3, a transverse quadrilateral unit 3 is provided, including two radial quadrilateral units 31 located on two opposite sides thereof, the two radial quadrilateral units 31 have the same structure but are inverted upside down, and the two radial quadrilateral units 31 are connected by a first cross bar 32 and a second cross bar 36; two adjacent transverse quadrilateral units 3 are connected by two third cross bars 35, and the two ends of the third cross bar 35 are respectively connected to the radial quadrilateral units 31 in the two adjacent transverse quadrilateral units 3.

In addition, the radial quadrilateral unit 31 includes an inner vertical rod 311 and an outer vertical rod 312. The inner vertical rod 311 and the outer vertical rod 312 have the same length and are arranged in parallel. A hingeless base 313 and a hinged base 314 are respectively arranged at the two ends of the inner vertical rod 311 and the outer vertical rod 312. The hingeless base 313 and the hinged base 314 fix the inner vertical rod 311 and the outer vertical rod 312. The slider 315 is mounted on the inner vertical rod 311 and the outer vertical rod 312, and can slide up and down along the inner vertical rod 311 and the outer vertical rod 312.

Example 3

The annular-radial rib-type deployable antenna structure of the present invention has a structure as shown in Figures 1 and 2, with an annular truss structure on the outside and a three-fold rib structure on the inside. The internal rib structures are all connected to the base 2 located at the center of the entire antenna structure. The external annular truss structure is mainly responsible for driving the antenna to unfold. The structure is composed of a plurality of mutually connected transverse quadrilateral units 3. As shown in Figure 3, both ends of each transverse quadrilateral unit 3 are radial quadrilateral units 31. The two radial quadrilateral units 31 have the same structure but are inverted upside down. Each radial quadrilateral unit 31 is composed of an inner vertical rod 311, an outer vertical rod 312, a hingeless base 313, a hinged base 314 and a slider 315. The inner vertical rod 311 and the outer vertical rod 312 are of the same length and are arranged in parallel. The hingeless base 313 and the hinged base 314 are respectively arranged at the two ends of the two vertical rods and the two vertical rods are fixedly connected to form a closed and stable radial quadrilateral unit 31. The slider 315 is sleeved on the inner vertical rod 311 and the outer vertical rod 312, and can slide up and down along the inner vertical rod 311 and the outer vertical rod 312. The two radial quadrilateral units 31 are connected by the first crossbar 32 and the second crossbar 36. Both ends of each crossbar are provided with pipe joints 33. The pipe joints 33 are hinged to the hinge connection part of the hinge base 314 or the slider 315 through the hinge connection mechanism 34. The pipe joint 33 at one end of the crossbar is hinged to the hinge base 314 of one radial quadrilateral unit 31, and the pipe joint 33 at the other end is hinged to the slider 315 of the other radial quadrilateral unit 31, thereby realizing the connection between the two radial quadrilateral units 31. The end of the crossbar connected to the slider 315 can move back and forth along the vertical rod as the slider 315 moves. When the external annular truss is in the folded state, the first crossbar 32 and the second crossbar 36 are in the same plane and do not interfere with each other, which reduces the radial size of the structure, so that the antenna structure of the present invention effectively saves limited space. As shown in FIG4 , the hinge connection part of the slider 315, the hinge base 314 and the pipe joint 33 are all provided with two holes. The hinge connection mechanism 34 includes a pulley 341, and bearings 342 are provided on both sides of the pulley 341. The pulley 341 and the two bearings 342 are both provided on the inner side of the hinge connection part, and washers 343 and sleeves 344 are provided on the outer side in sequence. The pin a345 passes through all parts and holes and is connected with the nut a346, thereby realizing the hinge connection between the pipe joint 33 and the slider 315 or the hinge base 314. The pin a345 and the nut a346 are connected together to form a revolute pair, which reduces the friction of the cross bar a32 when it rotates.

As shown in Figure 1, two third cross bars 35 are used to connect the two transverse quadrilateral units 3. Specifically, the third cross bar 35 is connected to the radial quadrilateral unit 31 of the transverse quadrilateral unit 3. The specific connection method is the same as the connection method between the first cross bar 32 or the second cross bar 36 and the radial quadrilateral unit 31, and the connection is achieved through a pipe joint 33 and a hinge connection mechanism 34.

As shown in FIG. 1 and FIG. 3 , two steel wire ropes 38 are connected between all adjacent radial quadrilateral units 31 , and the two ends of the steel wire ropes 38 are respectively connected to a hinged base 314 and a slider 315 at a diagonal position. The two steel wire ropes 38 cross each other to form a stable triangle, thereby improving the rigidity and stability of the external annular expandable truss.

As shown in Fig. 1 and Fig. 2, the interior of the antenna structure of the present invention is a parabolic three-fold rib structure, each three-fold rib is composed of a first rib 4, a middle rib 6, and a last rib 7. The first rib 4, the middle rib 6, and the last rib 7 are sequentially connected to the connecting mechanism 5 through the inter-rib locking to form a revolving pair. As shown in Fig. 5, the inter-rib locking and connecting mechanism 5 includes two connecting blocks a51 arranged on both sides of a to-be-connected part and two connecting blocks b52 arranged above another to-be-connected part. The connecting block b52 is located on the inner side of the connecting block a51. The connecting blocks a51 and b52 are both provided with connecting holes 53. The four connecting holes 53 are coaxial. The pin shaft b54 passes through the four connecting holes 53 and is connected and fixed with the nut b55. In addition, the connecting block a51 is provided with a positioning hole 56, and the connecting block b52 is provided with a mounting hole 57. The positioning hole 56 is a countersunk hole, and the mounting hole 57 is a through hole. A positioning pin shaft 58 is arranged in the mounting hole 57, and a spring 59 is arranged between the two positioning pin shafts 58. When the antenna is in an undeployed state, the positioning hole 56 and the mounting hole 57 are not coaxial, and the spring 59 is in a compressed state; when the three-fold rib structure is unfolded to a predetermined position, the positioning hole 56 and the mounting hole 57 are coaxial, and the spring 59 releases its elastic potential energy, pushing the two positioning pins 58 into the positioning holes 56 on both sides to achieve locking.

The first section rib 4 of the three-fold rib structure is connected to the transverse quadrilateral unit 3 of the external expandable annular truss through the rib connector 37 and the inter-rib locking and connecting mechanism 5, wherein the rib connector 37 is connected to the transverse quadrilateral unit 3, and then connected to the first section rib 4 through the inter-rib locking and connecting mechanism 5. The last section rib 7 of the three-fold rib structure is connected to the base 2 through the end rib connector 1, and forms a revolute pair. As shown in FIG6 , the end rib connector 1 includes an end rib connector 11 and a rib base 12, the end rib connector 11 is connected to the end rib 7 through a screw 13, the rib base 12 is fixed to the base 2 of the antenna, and the end rib connector 11 is hinged to the rib base 12 through a pin c14 and a nut c15.

In addition, as shown in FIG1 , a parabolic metal wire mesh 8 is connected from the bottom end of the outer annular truss structure to the base 2, which forms a back-to-back structure with the tri-fold rib structure. The metal wire mesh parabola has the same parameters as the working parabola of the deployable truss. Each metal wire is connected to the tri-fold rib surface cable net through five vertical adjustment cables 81. The five adjustment cables 81 are evenly distributed along each main cable, and the positions of the nodes of the tri-fold rib surface cable net are adjusted accordingly. The adjustment of the working parabola of the deployable truss is achieved by controlling the vertical adjustment cables to ensure the surface accuracy of the antenna cable net.

The driving mode of the deployable antenna structure of the present invention is rope drive, and there are two driving ropes 9, which are respectively connected in series with the upper and lower parts of the external annular truss structure. As shown in FIG7 , the driving rope 9 enters the first cross bar 32 or the second cross bar 36 through the slider 315, and after coming out of the first cross bar 32 or the second cross bar 36, it bypasses the hinged base 314 and enters the third cross bar 35, and circulates in this way to connect the upper or lower part of the external annular truss structure in series.

When the antenna begins to unfold, the driving cable 9 is continuously tightened, and the slider 315 continuously slides toward the hingeless base 313 under the action of the driving cable 9, and the left and right ends of the crossbar rotate clockwise around the hinged base 314 and the slider 315 through the pin a345 respectively. As the angle of the crossbar changes continuously, the diameter of the external annular truss structure also increases, and the first section rib 4 begins to rotate around the rib connector 37 through the pin b54, the middle section rib 6 begins to rotate around the first section rib 4 through the pin b54, and the last section rib 7 rotates relatively around the middle section rib 6 and the base 2 through the pin b54 and the pin c14. When fully unfolded, the shape of the antenna is as shown in Figure 1, the crossbar is in a horizontal state, and the curve formed by the three-fold rib is the antenna working parabolic curve, and at this time, the rib inter-locking and connecting mechanism 5 are locked, the rib shape is fixed and no longer changes, and the structural stability of the unfoldable truss is also increased. In the antenna truss structure of this embodiment, there are 2 ropes for driving the antenna structure to unfold. There are 9 external transverse quadrilateral units 3. When folded, the diameter is only 200 mm and the height is 300 mm. The diameter after unfolding is 2 m.

In summary, the antenna structure of the present invention adopts an external annular truss and an internal rib structure design. While meeting the antenna aperture requirements, it has a high storage ratio and high rigidity. At the same time, its surface accuracy is higher than that of the annular truss deployable antenna, and can be used in bands with higher precision requirements.

Claims (10)

1. A circular-radial rib-type deployable antenna structure, characterized in that it comprises an external circular truss structure and an internal tri-fold rib structure, wherein one end of the tri-fold rib structure is connected to the circular truss structure, and the other end is connected to a base (2) located at the center of the entire antenna structure; the circular truss structure is composed of a plurality of transverse quadrilateral units (3) connected together, and the tri-fold rib structure is composed of a first section rib (4), a middle section rib (6), and a last section rib (7) connected in sequence; a mesh parabolic metal wire mesh (8) is connected from the bottom end of the external circular truss structure to the base (2), and forms a back-to-back structure with the tri-fold rib structure, and each metal wire is connected to the tri-fold rib surface cable net through a plurality of vertical adjustment cables (81). 2. According to claim 1, the annular-radial rib type expandable antenna structure is characterized in that the lateral quadrilateral unit (3) includes two radial quadrilateral units (31) located on two opposite sides thereof, the two radial quadrilateral units (31) have the same structure but are inverted upside down, and the two radial quadrilateral units (31) are connected by a first cross bar (32) and a second cross bar (36); two adjacent lateral quadrilateral units (3) are connected by two third cross bars (35), and the two ends of the third cross bar (35) are respectively connected to the radial quadrilateral units (31) in the two adjacent lateral quadrilateral units (3). 3. According to claim 2, the annular-radial rib-type deployable antenna structure is characterized in that the radial quadrilateral unit (31) includes an inner vertical rod (311) and an outer vertical rod (312), the inner vertical rod (311) and the outer vertical rod (312) are of the same length and are arranged in parallel, and a hingeless base (313) and a hinged base (314) are respectively arranged at both ends of the inner vertical rod (311) and the outer vertical rod (312), and the hingeless base (313) and the hinged base (314) fix the inner vertical rod (311) and the outer vertical rod (312) to be fixedly connected, and a slider (315) is sleeved on the inner vertical rod (311) and the outer vertical rod (312), and can slide up and down along the inner vertical rod (311) and the outer vertical rod (312). 4. The annular-radial rib-type deployable antenna structure according to claim 3 is characterized in that both ends of the cross bar (32, 35, 36) are provided with pipe joints (33), and the pipe joints (33) at both ends are respectively hinged to the hinge base (314) and the slider (315) in two adjacent radial quadrilateral units (31) through a hinge connection mechanism (34). 5. According to claim 4, the annular-radial rib type deployable antenna structure is characterized in that the slider (315), the hinge connection part including the hinge base (314) and the pipe joint (33) are all provided with two holes; the hinge connection mechanism (34) includes a pulley (341), and bearings (342) are provided on both sides of the pulley (341); the pulley (341) and the two bearings (342) are all arranged on the inner side of the hinge connection part, and washers (343) and sleeves (344) are arranged on the outer side thereof in sequence; and the pin a (345) passes through all parts and holes and is connected to the nut a (346). 6. The annular-radial rib expandable antenna structure according to claim 3 is characterized in that two adjacent radial quadrilateral units (31) are connected with two steel wire ropes (38), the two steel wire ropes (38) cross each other, and their two ends are respectively connected to a hinged base (314) and a slider (315) at a diagonal position. 7. According to claim 1, the annular-radial rib-type expandable antenna structure is characterized in that the first section ribs (4), the middle section ribs (6), and the last section ribs (7) are connected in sequence through the inter-rib locking and connecting mechanism (5); the first section ribs (4) are connected to the transverse quadrilateral units (3) of the external annular truss through rib connectors (37) and the inter-rib locking and connecting mechanism (5), wherein the rib connectors (37) are connected to the transverse quadrilateral units (3), and then connected to the first section ribs (4) through the inter-rib locking and connecting mechanism (5); the last section ribs (7) of the three-fold rib structure are connected to the base (2) through the end rib connecting mechanism (1). 8. The annular-radial rib-type deployable antenna structure according to claim 7 is characterized in that the inter-rib locking and connecting mechanism (5) comprises two connecting blocks a (51) arranged on both sides of a to-be-connected member and two connecting blocks b (52) arranged above another to-be-connected member, the connecting block b (52) being located on the inner side of the connecting block a (51), the connecting block a (51) and the connecting block b (52) being both provided with connecting holes (53), the four connecting holes (53) being coaxial, the pin shaft b (54) passing through the four connecting holes (53) and then being connected and fixed with the nut b (55); the connecting block a (51) being provided with a positioning hole (53) 6), a mounting hole (57) is provided on the connecting block b (52), the positioning hole (56) is a countersunk hole, the mounting hole (57) is a through hole, a positioning pin shaft (58) is provided in the mounting hole (57), and a spring (59) is provided between the two positioning pin shafts (58); when the antenna is in an unfolded state, the positioning hole (56) and the mounting hole (57) are not coaxial, and the spring (59) is in a compressed state; when the three-fold rib structure is unfolded to a predetermined position, the positioning hole (56) and the mounting hole (57) are coaxial, and the spring (59) releases elastic potential energy, and pushes the two positioning pin shafts (58) into the positioning holes (56) on both sides to achieve locking. 9. The annular-radial rib type expandable antenna structure according to claim 7 is characterized in that the end rib connection mechanism (1) includes an end rib connection member (11) and a rib base (12), the end rib connection member (11) is fixedly connected to the end rib (7), the rib base (12) is fixed to the base (2) of the antenna, and the end rib connection member (11) is hinged to the rib base (12) through a pin shaft c (14) and a nut c (15). 10. According to claim 1, the annular-radial rib type expandable antenna structure is characterized in that the antenna structure is driven by rope, and there are two driving ropes (9) in total, which are respectively connected in series with the upper and lower parts of the external annular truss structure; the driving rope (9) enters the first cross bar (32) or the second cross bar (36) through the slider (315), and after coming out of the first cross bar (32) or the second cross bar (36), it bypasses the hinged base (314) and enters the third cross bar (35), and circulates in this way to connect the upper or lower part of the external annular truss structure in series.