CN108417991B

CN108417991B - Synchronously-deployable ring beam for annular truss type reflector

Info

Publication number: CN108417991B
Application number: CN201810074048.5A
Authority: CN
Inventors: 赵治华; 付康佳; 任革学
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2018-01-25
Filing date: 2018-01-25
Publication date: 2020-09-15
Anticipated expiration: 2038-01-25
Also published as: CN108417991A

Abstract

The invention provides a synchronously-deployable ring beam for an annular truss type reflector, which belongs to the technical field of satellite antennas and is formed by connecting a plurality of same basic quadrilateral units which are distributed annularly, wherein each basic quadrilateral unit comprises two longitudinal rods, two transverse rods, an oblique rod and two same synchronous deployment mechanisms; each synchronous unfolding mechanism comprises a sliding hinge, a synchronous rope and three pulleys which are arranged in a matched manner; the sliding hinge is positioned on one longitudinal rod, and the sliding hinge and the T-shaped hinge positioned on the other longitudinal rod are respectively connected with two ends of one transverse rod through revolute pairs; the first pulley and the second pulley are fixed on the sliding hinge and are both tangent to the synchronous rope, and the third pulley is fixed on the T-shaped hinge of the other longitudinal rod; one end of the synchronous rope is fixed on the longitudinal rod fixing joint of one longitudinal rod, and the other end of the synchronous rope is sequentially wound around the three pulleys and then is fixedly connected with the sliding hinge on the other longitudinal rod. The invention has the characteristics of simple structure, good synchronism, and constant synchronous rope length and tension value.

Description

Synchronously-deployable ring beam for annular truss type reflector

Technical Field

The invention belongs to the technical field of satellite antennas, and relates to a synchronously-deployable ring beam for an annular truss type reflector.

Background

In recent years, with the increasing demands for communication, deep space exploration and the like, the aperture of the satellite antenna is gradually increased. However, due to the limited space for rocket launching, a satellite antenna capable of being deployed needs to be developed. The circular truss type deployable (understood to be both deployable and collapsible) reflector Astromesh (us patent No.5680145) is one of the typical successors of deployable satellite antennas, which has the advantages of light weight, high stiffness, high contraction ratio and easy deployment. The Astromesh reflector is composed of an expandable ring beam and a net surface supported by the ring beam, wherein the ring beam can realize the transformation of the ring reflector from a folded state to an expanded state (currently, the ring reflector is maintained in the state after being completely expanded). Specifically, the ring beam is a periodic structure distributed along the ring direction, and is formed by connecting all identical quadrilateral units, and the quadrilateral units can be folded and unfolded, see fig. 1, where fig. (a) is a configuration schematic diagram of the ring beam in the middle process of unfolding, and fig. (b) is a configuration schematic diagram of the ring beam fully unfolded. The annular reflector can be divided into a first generation configuration (abbreviated as AM1) and a second generation configuration (abbreviated as AM2) according to the difference of folding modes. The AM2 is characterized in that the folding height is reduced by adopting a mode that a sliding hinge slides along a longitudinal rod, and the AM2 folding height is reduced by 40% compared with the AM1 under the same focal ratio. The AM2 is suitable for realizing a larger caliber toroidal reflector, considering that the space for rocket transport is limited and the height of the AM2 is smaller when the device is folded.

For the expandable ring beam of the ring reflector with the second generation configuration, referring to (c) and (d) in fig. 1, each quadrilateral unit in the ring beam respectively comprises 2 parallel longitudinal rods (3 and 9) with equal length, 2 transverse rods (6 and 11) with equal length and 1 oblique rod 12, two ends of each longitudinal rod are respectively fixed with a longitudinal rod fixing joint (1 and 7) and a T-shaped hinge (4 and 10), the longitudinal rod fixing joints and the T-shaped hinges on the two longitudinal rods (3 and 9) are arranged diagonally, and two ends of the oblique rod 12 are respectively connected with 1T-shaped hinge through revolute pairs. Each of the substantially quadrilateral elements of the ring beam is rectangular when in the fully deployed state. The key of the expansion of the ring beam is that each quadrilateral unit is synchronously expanded, namely, the movement of each basic quadrilateral unit is ensured to be consistent. For this purpose, two synchronous deployment mechanisms are further provided in each basic quadrilateral unit of the existing ring beam, and each synchronous deployment mechanism ensures that the adjacent sliding hinges slide on the longitudinal bars for the same distance through a group of synchronous ropes passing around the pulleys. For one of the synchronous unfolding mechanisms (positioned at the lower left), the synchronous unfolding mechanism specifically comprises a sliding hinge 2, a synchronous rope 13 and two pulleys (5 and 14) which are arranged in a matched manner, and the other synchronous unfolding mechanism (positioned at the upper right) is similar to the synchronous unfolding mechanism; each sliding hinge is respectively positioned on 1 longitudinal rod and can slide up and down along the corresponding longitudinal rod; each sliding hinge and the T-shaped hinge positioned on the other longitudinal rod are respectively connected with two ends of the corresponding transverse rod through revolute pairs; the two pulleys are respectively fixed on a T-shaped hinge and a sliding hinge which are fixedly connected with different longitudinal rods; the lower synchronous rope 13 respectively bypasses the two

pulleys

5 and 14 at two inflection points, one end of the lower synchronous rope 13 is fixed on the left sliding hinge 2, and the other end is fixed on the right longitudinal rod fixed joint 7. The upper synchronization rope 16 is arranged and wound like the lower synchronization rope 13. During the movement of the basic quadrilateral unit from folding to unfolding, the wrap angle (the central angle corresponding to the contact arc length of the synchronous rope and the pulley) of each pulley is reduced from about 180 degrees to about 90 degrees, and the length of the whole synchronous rope is changed during the unfolding process considering that the size of the pulley is not negligible. If the synchronous rope is tensioned in a furled state, the synchronous rope can be gradually loosened in an unfolding process, so that the synchronous effect is greatly weakened, the movement consistency of each quadrilateral unit cannot be ensured, and even the ring beam cannot be completely unfolded in severe cases.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides the synchronously-expandable ring beam for the annular truss type reflector, can realize the synchronous expansion of all basic quadrilateral units of the ring beam, and has the characteristics of simple form and easy realization.

In order to realize the purpose of the invention, the following technical scheme is adopted:

a synchronously expandable ring beam for an annular truss type reflector is formed by connecting a plurality of same basic quadrilateral units distributed along the circumferential direction, each basic quadrilateral unit respectively comprises two longitudinal rods, two transverse rods, an inclined rod and two same synchronous expansion mechanisms, a longitudinal rod fixed joint and a T-shaped hinge are respectively fixed at two ends of each longitudinal rod, the longitudinal rod fixed joints and the T-shaped hinges on the two longitudinal rods are arranged in opposite angles, and two ends of the inclined rod are respectively connected with one T-shaped hinge through revolute pairs; two adjacent basic quadrilateral units share one longitudinal rod, and the two basic quadrilateral units are symmetrically arranged around the longitudinal rod;

each synchronous unfolding mechanism comprises a sliding hinge, a synchronous rope with a fixed rope length and three pulleys which are arranged in a matched manner; the sliding hinge is positioned on one longitudinal rod and slides up and down along the longitudinal rod, and the sliding hinge and the T-shaped hinge positioned on the other longitudinal rod are respectively connected with two ends of one transverse rod through revolute pairs; the first pulley and the second pulley are fixed on the sliding hinge and are both tangent to the synchronous rope, the third pulley is fixed on the T-shaped hinge of the other longitudinal rod, one end of the synchronous rope is fixed on the longitudinal rod fixing joint of one longitudinal rod, and the other end of the synchronous rope is fixedly connected with the sliding hinge on the other longitudinal rod after sequentially passing around the three pulleys;

the arrangement of three pulleys also needs to meet the following requirements: the second pulley and the third pulley have equal radius; the circle centers of the second pulley and the third pulley are respectively superposed with the rotating centers of two ends of a cross rod; the horizontal distance between the circle center of the second pulley and the corresponding cross rod is closer than that of the first pulley, meanwhile, the vertical distance between the circle center of the second pulley and the fixed joint of the longitudinal rod on the corresponding longitudinal rod is closer than that of the first pulley, the direction of the synchronous rope between the first pulley and the fixed joint of the longitudinal rod on the corresponding longitudinal rod and the direction of the synchronous rope between the first pulley and the second pulley are both parallel to the longitudinal rod, and the direction of the synchronous rope between the sliding hinge on the third pulley and the other longitudinal rod is parallel to the other longitudinal rod;

two simultaneous deployment mechanisms are arranged in central symmetry about the geometric centroid of the substantially quadrilateral unit.

The invention has the beneficial effects that:

the synchronously deployable ring beam for the annular truss type reflector provided by the invention has the advantages that the synchronous deployment mechanism is improved, the length of the synchronous rope in the deployment process of the annular reflector is ensured not to change along with the change of the configuration of the basic quadrilateral units, and therefore, all sliding hinges in the ring beam generate the same displacement, and the movement synchronism of all the basic quadrilateral units is ensured. The invention has the characteristics of simple structure, good synchronism, and constant length and tension value of the synchronous rope.

Drawings

Fig. 1 is an expanded schematic view of a ring beam in a prior art Astromesh second generation configuration (AM2), fig. (a) is a configuration schematic view of an intermediate process of ring beam expansion, fig. (b) is a configuration schematic view of a ring beam which is completely expanded, fig. (c) is a structural schematic view of a basic quadrilateral unit in fig. (a), and fig. (d) is a structural schematic view of a basic quadrilateral unit in fig. (b).

Fig. 2 is a schematic structural view of a basic quadrilateral unit of the ring beam in a folded state.

Fig. 3 is a schematic structural view of a substantially quadrangular unit of the ring beam of the present invention in a fully unfolded state.

Fig. 4 shows the sliding distances of the left and right slide hinges in the present embodiment.

Fig. 5 shows the length change of the upper and lower synchronous ropes in the present embodiment.

Fig. 6 is a graph of the difference between the slip distance and the input distance of the present embodiment.

Detailed Description

The synchronously deployable ring beam of the annular truss type reflector provided by the invention is further described by combining the attached drawings and an embodiment as follows:

the invention provides a synchronously-deployable ring beam for an annular truss type reflector, which is formed by connecting a plurality of basic quadrilateral units which are distributed along the circumferential direction and have the same structure, wherein each basic quadrilateral unit respectively comprises two parallel longitudinal rods with equal length, two transverse rods with equal length and an inclined rod, two ends of each longitudinal rod are respectively and fixedly connected with a longitudinal rod fixed joint and a T-shaped hinge, the longitudinal rod fixed joints and the T-shaped hinges on the two longitudinal rods are arranged in opposite angles, and two ends of the inclined rod are respectively connected with one T-shaped hinge through a revolute pair; two adjacent basic quadrilateral units share one longitudinal rod, and the two basic quadrilateral units are symmetrically arranged around the longitudinal rod; each basic quadrilateral unit also comprises two same synchronous unfolding mechanisms respectively, and each synchronous unfolding mechanism comprises a sliding hinge, a synchronous rope with a fixed rope length and three pulleys which are arranged in a matched manner; the sliding hinge is positioned on one longitudinal rod and can slide up and down along the longitudinal rod; the sliding hinge and the T-shaped hinge on the other longitudinal rod are respectively connected with two ends of a cross rod through revolute pairs, a first pulley and a second pulley are fixed on the sliding hinge of one longitudinal rod and are both tangent to a synchronous rope, a third pulley is fixed on the T-shaped hinge of the other longitudinal rod, one end of the synchronous rope is fixed on a longitudinal rod fixed joint of one longitudinal rod, and the other end of the synchronous rope is fixedly connected with the sliding hinge on the other longitudinal rod after sequentially passing around the three pulleys; the arrangement of three pulleys also needs to meet the following requirements: (1) the radius of the second pulley is equal to that of the third pulley; (2) the circle centers of the second pulley and the third pulley are respectively superposed with the rotating centers of two ends of a cross rod; (3) the horizontal distance between the circle center of the second pulley and the corresponding cross rod is closer than that of the first pulley, meanwhile, the vertical distance between the circle center of the second pulley and the fixed joint of the longitudinal rod on the corresponding longitudinal rod is closer than that of the first pulley, the directions of the synchronous ropes between the first pulley and the fixed joint of the longitudinal rod on one longitudinal rod and between the first pulley and the second pulley are parallel to the longitudinal rod, and the direction of the synchronous ropes between the sliding hinges from the third pulley and the other longitudinal rod is parallel to the other longitudinal rod; two simultaneous deployment mechanisms are arranged in central symmetry about the geometric centroid of the substantially quadrilateral unit.

In the unfolding motion process of the basic quadrilateral unit, the improved synchronous unfolding mechanism can ensure that each section of the synchronous rope is parallel to the corresponding transverse rod and the corresponding longitudinal rod respectively; the wrap angle of the synchronous rope, which bypasses the pulley on the sliding hinge and close to the longitudinal rod, is always kept unchanged and is constant at 180 degrees; the wrap angle of the synchronous rope passing through the pulley on the T-shaped hinge is gradually reduced along with the increase of the unfolding degree of the basic quadrilateral unit, but the wrap angle of the synchronous rope passing through the pulley on the sliding hinge far away from the longitudinal rod is gradually increased along with the increase of the unfolding degree of the basic quadrilateral unit, and the sum of the two wrap angles is constantly 180 degrees as shown in geometry, so the total length of the synchronous rope can be kept constant in the unfolding process. When the annular truss type reflector is unfolded, the sliding hinge on one side moves from the middle position of the longitudinal rod to the top end of the longitudinal rod, and therefore under the action of the synchronous rope, the sliding hinge on the other side also moves for the same distance. Considering that all the basic quadrilateral units are connected in series to form a whole-circle ring beam, the synchronous unfolding mechanism can ensure that the sliding hinges on each longitudinal rod move for the same distance, so that the unfolding processes of all the units are kept synchronous, and the tension value of the synchronous ropes is kept unchanged. When the basic quadrilateral unit is in an unfolded state, the wrap angle (central angle corresponding to the arc length of the contact part) of the synchronous rope on the pulley of the sliding hinge close to the cross rod is equal to 90 degrees.

Example (b):

the specific structure of this embodiment is shown in fig. 2 and 3. Fig. 2 shows a transition state (between a folded state and an unfolded state) of a basic quadrilateral unit in the deployable ring beam of the Astromesh second-generation configuration of the annular truss-type reflector shown in fig. 1, and fig. 3 shows an unfolded state of the basic quadrilateral unit. The assembly of a basic quadrilateral unit comprises a left longitudinal rod 3 and a right longitudinal rod 9 which are parallel and equal in length, a lower cross rod 6 and an upper cross rod 11 which are equal in length, and 1 inclined rod 12, wherein an upper longitudinal rod fixed joint 1 and a lower T-shaped hinge 4 are respectively fixed at two ends of the left longitudinal rod 3, a lower longitudinal rod fixed joint 7 and an upper T-shaped hinge 10 are respectively fixed at two ends of the right longitudinal rod 9, the longitudinal rod fixed joints and the T-shaped hinges on the two longitudinal rods (3 and 9) are arranged diagonally, and two ends of the inclined rod 12 are respectively connected with the 1T-shaped hinge through revolute pairs. Each basic quadrilateral unit also comprises two same synchronous unfolding mechanisms respectively, each synchronous unfolding mechanism comprises a sliding hinge, a synchronous rope with a fixed rope length and three pulleys which are arranged in a matched manner, and the details are explained by taking one synchronous unfolding mechanism as an example. The sliding hinge 8 is positioned on the right vertical rod and can slide up and down along the vertical rod, the sliding hinge and the T-shaped hinge 4 positioned on the left vertical rod 3 are respectively connected with two ends of the lower transverse rod 6 through revolute pairs, the pulley 15 and the pulley 14 are both fixed on the sliding hinge 8 of the right vertical rod 9 and are both tangent to the synchronous rope 13, the pulley 5 is fixed on the T-shaped hinge 4 of the right vertical rod 3, one end of the synchronous rope 13 is fixed on the vertical rod fixed joint 7 of the right vertical rod 9, the other end of the synchronous rope 13 is sequentially wound around the three pulleys and then fixedly connected with the sliding hinge 2 on the left vertical rod 3 (specifically, the other end of the synchronous rope 13 is firstly parallel to the right vertical rod 9 upwards, then is parallel to the right vertical rod 9 downwards after being wound around the pulley 15 on the sliding hinge 8, then is parallel to the lower transverse rod 6 leftwards after being wound around the pulley 14, then is parallel to the left vertical rod 3 upwards after being wound around the pulley 5 on the T-shaped hinge, in order to ensure that the length of the synchronous rope is unchanged in the unfolding process, the three pulleys also meet the following requirements: (1) pulley 14 and pulley 5 are equal in radius, and the radius of pulley 15 is not required to be equal to

pulleys

5 and 14; (2) the centers of circles of the pulley 14 and the pulley 5 are respectively superposed with the rotating centers of the two ends of the lower cross rod 6; (3) the horizontal distance between the center of the pulley 14 and the lower cross bar 6 is smaller than that between the center of the pulley 15 and the pulley 15, and the vertical distance between the center of the pulley 14 and the vertical bar fixed joint 7 on the right vertical bar 9 is smaller than that between the pulley 15 and the pulley 15. The direction of the synchronous rope between the pulley 15 and the vertical rod fixing joint 7 on the right vertical rod 9 and between the pulley 15 and the pulley 14 is parallel to the right vertical rod 9, and the direction of the synchronous rope between the pulley 5 and the sliding hinge 2 on the left vertical rod 3 is parallel to the left vertical rod 3. Specifically, the circle center position of the pulley 15 is located at the upper right of the pulley 14, the horizontal position of the pulley 15 relative to the pulley 14 needs to keep the synchronization rope 13 between the two pulleys parallel to the right vertical rod 9, the vertical position of the pulley 15 only needs to be located above the pulley 14, and the specific size is not required; the two synchronous deployment mechanisms are arranged in central symmetry about the geometric centroid of the basic quadrilateral unit, and the other synchronous rope 16 is arranged in a manner similar to that of the synchronous rope 13, which is not described in detail herein. In actual work, the sliding of the sliding hinges along the longitudinal rod is realized through the driving ropes controlled by the motor, but the sliding of the sliding hinges along the longitudinal rod by the same distance cannot be guaranteed, so that the synchronous unfolding mechanism is needed to guarantee that the sliding hinges slide by the same distance, and further guarantee the synchronism of the unfolding of the basic quadrilateral units of the ring beam. Since the synchronous rope driving mechanism is independent and independent from the synchronous unwinding mechanism, the implementation scheme of the driving mechanism is not described in detail herein.

The dimensions of the components in this example are as follows: the ring beam is formed by connecting 6 basic quadrilateral units in a ring direction, the caliber of the ring beam is 2 meters when the ring beam is completely unfolded, the length of each transverse rod is 530.2mm, the length of each longitudinal rod is 1384.7mm, and the radius of each pulley is 7 mm; the mounting distance of the two pulleys on the T-shaped hinge is 97 mm; 4 pulleys (used by two adjacent quadrilateral units) are required to be installed on the sliding hinge, the two pulleys can be divided into two groups according to symmetry about the center line of the sliding hinge, the installation distance of one group of two pulleys close to each other is 69mm, and the installation distance of the other group of two pulleys is 97 mm; the lengths of the two synchronous ropes are 1970.9 mm. Each component is a conventional part.

Example validation:

firstly, the effectiveness of the scheme of synchronously winding the rope around the pulley with the rope length kept unchanged in the unfolding process is verified through simulation. A basic quadrilateral unit is established, which is in a fully unfolded state at the initial moment, and displacement drive is applied to the sliding hinge 2 so that the sliding hinge gradually slides downwards along the left longitudinal rod 3 from the top end. Under the action of the synchronous rope, the sliding hinge 8 at the right side slides upwards, so that the basic quadrilateral unit is gradually folded. The sliding distance of the sliding hinge 2 and the sliding hinge 8 changes with time as shown in fig. 4, and it can be seen that the displacements of the two are kept the same. Then, the sliding hinge 2 is driven to move upwards along the left vertical rod 3, and the right sliding hinge 8 slides downwards under the action of the synchronous rope, so that the basic quadrilateral unit is unfolded gradually and completely. The sliding distances of the two sliding

hinges

2 and 8 on the longitudinal rod in the unfolding process are quantitatively counted, as shown in fig. 4, it can be seen that the two sliding

hinges

2 and 8 can both guarantee the same displacement in the whole unfolding process, i.e. the synchronism of the movement can be guaranteed. In addition, the variation of the lengths of the upper synchronization rope 16 and the lower synchronization rope 13 during the unwinding process is also counted, as shown in fig. 5. It can be seen that the length of the synchronization cord can remain constant during deployment.

Then, the number of the sliding hinges is 0 to 6 in sequence, the sliding hinge No. 0 is an active displacement driving end, the rest points are all in passive motion under the action of the synchronous rope, and the displacement delta of each sliding hinge is measured_iI is 1,2, …, 5. When the movement amount of the sliding hinge is less than 150mm, measuring by using a vernier caliper, wherein the measurement error amount is about +/-1 mm; when the diameter is larger than 150mm, the measuring error is about +/-2 mm. The active driving end enables the displacement delta on the No. 0 sliding hinge₀First increasing from 0 to 686mm (ring beam furling phase) and then decreasing from 686mm to 0mm (ring beam unfolding phase). The difference between the displacement of the sliding hinge No. 1-5 and the displacement of the sliding hinge at the input end No. 0 is obtained from the measurement results, and the result is shown in FIG. 6. It can be seen that the maximum difference occurs in the deployed state, about 10mm, and the maximum difference in the intermediate state of motion is about 6 mm. Considering the errors of machining and assembling, the invention has good synchronism in the experiment.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the invention, which is intended to include all modifications, equivalents, improvements, etc. that are within the spirit and scope of the invention.

Claims

1. A synchronously expandable ring beam for an annular truss type reflector is formed by connecting a plurality of same basic quadrilateral units distributed along the circumferential direction, wherein each basic quadrilateral unit respectively comprises two longitudinal rods, two transverse rods, an inclined rod and two same synchronous expansion mechanisms; one end of each longitudinal rod is fixed with a longitudinal rod fixed joint, the other end of each longitudinal rod is fixed with a T-shaped hinge, the longitudinal rod fixed joints and the longitudinal rod fixed joints on the two longitudinal rods are arranged diagonally, and the T-shaped hinges are arranged diagonally; two ends of the diagonal rod are respectively connected with a T-shaped hinge through a revolute pair; two adjacent basic quadrilateral units share one longitudinal rod, and the two basic quadrilateral units are symmetrically arranged around the longitudinal rod; the method is characterized in that:

each synchronous unfolding mechanism comprises a sliding hinge, a synchronous rope with a fixed rope length and three pulleys which are arranged in a matched manner; the sliding hinge is positioned on one longitudinal rod and slides up and down along the longitudinal rod, the sliding hinge is connected with one end of one transverse rod through a revolute pair, and the T-shaped hinge positioned on the other longitudinal rod is connected with the other end of the transverse rod through a revolute pair; the first pulley and the second pulley are fixed on the sliding hinge and are both tangent to the synchronous rope, the third pulley is fixed on the T-shaped hinge of the other longitudinal rod, one end of the synchronous rope is fixed on the longitudinal rod fixing joint of one longitudinal rod, and the other end of the synchronous rope is fixedly connected with the sliding hinge on the other longitudinal rod after sequentially passing around the three pulleys;