A repeatable deployable space morphing platform and cable drive system

Abstract

The application discloses a space variable configuration platform and a rope driving system which can be repeatedly folded and unfolded. The platform comprises a flexible folding sail surface, a plurality of folding arms for supporting the flexible folding sail surface and a driving device for driving the movement of the folding arms. The folding arms are subjected to telescopic or bending deformation under the action of corresponding driving motors in the driving device. The flexible folding sail surface is connected with the folding arms. The driving device releases and withdraws the driving rope driven by the motor to realize the folding and unfolding control of the folding arms. Under the driving of the folding arms, the flexible folding sail surface can be deformed to increase or decrease the surface area of the antenna. The platform and the system can realize the repeated folding and unfolding of the antenna and the switching of a plurality of different configurations, so that the working range of the space unfoldable structure is expanded.

Description

Technical Field

[0001] This invention relates to the aerospace field, specifically to the field of deployable antennas and cable-driven technology, and in particular to a reusable deployable space variable configuration platform and cable-driven system. Background Technology

[0002] With the rapid development of aerospace technology, fixed-form satellite payloads can no longer meet the requirements of multi-mission execution capability, strong environmental adaptability and risk resistance. Space deployable structures provide an effective solution for this, which can realize the transformation from a tightly folded state to a controllable unfolding state to meet different application needs. They have been widely used in many fields such as solar cells, large-aperture spaceborne antennas, space station folding arms, and space robots.

[0003] However, most existing space deployable structures are single-use, with deployment mechanisms relying on springs, elastic materials, or drive ropes to provide the driving force. After deployment, they lock and maintain the deployed state. With the development of satellite technology, the size range of space deployable structures has increased, functional requirements have grown, and spacecraft maneuverability demands have become more stringent, leading to a growing need for reusable deployment and retrieval structures. Addressing the urgent needs of space applications for multifunctionality, lightweight structures, and reusability, this invention proposes a reusable, foldable, and variable-configuration space platform and rope-driven design. Unlike traditional space deployable structures, this invention enables repeated folding and unfolding of antennas, as well as switching between multiple different configurations. This invention significantly expands the operational scope of space deployable structures, applicable to solar cells, spaceborne antennas, space robots, and more. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to provide a reusable foldable and deployable spatial variable configuration platform and rope drive system, which can realize the repeated folding and unfolding of antennas and the switching of multiple different configurations, thereby expanding the working range of spatial deployable structures.

[0005] To achieve the above objectives, the present invention provides a reusable folding and unfolding spatial variable configuration platform. The platform includes a flexible folding sail, several folding arms supporting the flexible folding sail, and a drive device for driving the folding arms. The folding arms extend, contract, or bend under the action of corresponding drive motors within the drive device. The flexible folding sail is connected to the folding arms. The drive device controls the folding and unfolding of the arms by releasing and retracting drive ropes via motors. Under the drive of the folding arms, the flexible folding sail can deform, causing the antenna surface area to increase or decrease. When the lengths of the folding arms are all at their maximum L... max At that time, the area of ​​the flexible folding sail is at its maximum, which is S. max At this point, the antenna is in a fully deployed state; when the lengths of the folded arms are all at their minimum L...min At that time, the area of ​​the flexible folding sail is minimized to S. min At this point, the antenna is in a fully folded state; the length of the folded arm can also be set to L; where The folding arm is located at a length between its longest and shortest point, at which point the area of ​​the flexible folding sail surface is S. .

[0006] Furthermore, the folding arm includes multiple folding units. The folding arm is controlled by the drive device, which controls each folding unit, allowing the flexible folding sail to switch between a fully deployed state, a fully folded state, and a partially deployed state.

[0007] Furthermore, the flexible folding sail has a circular planar antenna configuration, with the driving device located at the center. Several folding arms extend radially from the driving device to the outer periphery of the flexible folding sail. One end of each folding arm is connected to the driving device, and the other end is connected to the edge of the flexible folding sail. The antenna folding and unfolding is achieved by controlling the extension and retraction of the folding arms.

[0008] Furthermore, the flexible folding sail has a parabolic antenna configuration, with the driving device located at the bottom of the parabola. Several folding arms extend radially from the driving device to the outer periphery of the flexible folding sail. One end of each folding arm is connected to the driving device, and the other end is connected to the edge of the flexible folding sail. The antenna folding and unfolding is achieved by controlling the bending of the folding arms.

[0009] Furthermore, the folding arm is composed of multiple folding units. Each folding unit has a square support base and a folding section. Each folding section includes two symmetrical, approximately triangular units, one of which has a rectangular section at one end. The square support base is fixed to the rectangular section at one end of one of the triangles and hinged to the base of the other triangle. Each folding arm is equipped with eight unfolding drive ropes for control.

[0010] On the other hand, the present invention also provides a rope drive system applied to a reusable folding and unfolding spatial variable configuration platform. Each folding and unfolding arm is provided with 8 unfolding drive ropes and 4 folding drive ropes, namely the first unfolding drive rope 111, the second unfolding drive rope 112, the third unfolding drive rope 121, the fourth unfolding drive rope 122, the fifth unfolding drive rope 131, the sixth unfolding drive rope 132, the seventh unfolding drive rope 141, and the eighth unfolding drive rope 142; and the first folding drive rope 113, the second folding drive rope 123, the third folding drive rope 133, and the fourth folding drive rope 143. Each side of the folding and unfolding arm is provided with two sets of retraction motors, which are responsible for the retraction drive and unfolding drive of that side, respectively.

[0011] Furthermore, under the action of the retracting motor, the first deployment drive rope 111 and the second deployment drive rope 112 are retracted and shortened; the routing of the first deployment drive rope 111 on the folding arm structure is as follows: The routing of the second deployment drive rope 112 on the folding arm structure is as follows: In this diagram, A is located near the bottom edge of the rectangle at one end of the lower triangle; C is located at the boundary between the triangular and rectangular parts of the lower triangle; B and D are located at the hinge pivots of the lower and upper triangles, respectively; E and F are located near the vertex of the triangular part of the lower triangle, respectively. The subscripts 1, 2, and 3 of each letter represent the numbers of each unfolding unit.

[0012] Furthermore, the end point of the first deployment drive rope 111 With folding arm structure The end of the second deployment drive rope 112 is fixed at the point of connection. With folding arm structure The connection is fixed at the point; under the action of the drive motor, the lengths of the two deployment drive ropes, the first deployment drive rope 111 and the second deployment drive rope 112, are shortened, and the folding arm structure goes from a fully folded state to a fully deployed state.

[0013] Furthermore, the first deployment drive rope 111 in It was passed through twice. The first time through The point only touches that point and does not move away from it. Passing through the hole a second time Point from It passes through the hole; therefore, during the deployment of the structure, the first deployment drive rope 111... Section, can be with The point of separation occurs; after crossing the critical configuration, the first deployment drive rope 111... Duan Yu When the point of contact ceases to exist, separation occurs; when the structure reaches configuration iii, the drive motor is de-energized, and under the action of the structure's elastic force, it eventually fully unfolds.

[0014] Furthermore, for the folding drive rope, the folding of the structure connected to it is achieved by shrinking the length of the folding drive rope. For the array structure composed of each bistable unit connected in series, only one folding drive rope is needed to achieve the complete folding of the series array structure. The motor at this location is a retracting motor, which retracts the folding drive rope to shorten it.

[0015] Beneficial effects: The present invention enables repeated folding and unfolding of the antenna, as well as switching between multiple different configurations, thereby expanding the working range of the space deployable structure. In particular, the unfolding driving rope and the folding driving rope adopt structurally different routing modes, which ensures that the structure can be both unfolded and folded under the control of different motors. Compared with hybrid driving modes (such as hybrid driving of pneumatic drive and motor rope drive), the driving mode is more single, so that the design of the control system supporting the structure is more concise. In addition, the adoption of this design facilitates the on-orbit application of the platform, and can better adapt to the space environment such as vacuum, alternating high and low temperatures. Brief Description of the Drawings

[0016] Figure 1 shows an overall schematic diagram of the repeatable foldable and deployable spaceborne variable configuration structure according to the present invention; Figure 2 shows a schematic diagram of the fully unfolded state of the repeatable foldable and deployable spaceborne variable configuration antenna according to the present invention; Figure 3 shows a schematic diagram of the fully folded state of the repeatable foldable and deployable spaceborne variable configuration antenna according to the present invention; Figure 4 shows a schematic diagram of the partially unfolded state of the repeatable foldable and deployable spaceborne variable configuration antenna according to the present invention; Figure 5 shows a schematic diagram of the planar structure of the repeatable foldable and deployable structure according to the present invention; Figure 6 shows a schematic diagram of the parabolic opening facing upward of the parabolic configuration of the repeatable foldable and deployable antenna according to the present invention; Figure 7 shows a schematic diagram of the parabolic opening facing downward of the parabolic configuration of the repeatable foldable and deployable antenna according to the present invention; Figure 8 shows a schematic diagram of the fully unfolded configuration of the unfolding driving rope of the foldable and deployable arm 1 according to the present invention; Figure 9 shows a schematic diagram of the fully folded configuration of the unfolding driving rope of the foldable and deployable arm 1 according to the present invention; Figure 10 shows a schematic front view of the fully unfolded configuration of the unfolding driving rope of the foldable and deployable arm 1 according to the present invention; Figure 11 shows a schematic front view of the fully folded configuration of the unfolding driving rope of the foldable and deployable arm 1 according to the present invention; Figure 12 shows a schematic diagram of the routing mode of the unfolding driving rope according to the present invention; Figure 13 shows a schematic diagram of the routing mode of the folding driving rope according to the present invention. Detailed Description of the Embodiments

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] The following combination Figures 1-13 Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.

[0021] exist Figure 1In the illustrated embodiment, the reusable foldable spatial configuration platform according to the present invention includes a flexible foldable sail 6, a plurality of foldable arms for supporting the flexible foldable sail, and a drive device 5 for driving the movement of the foldable arms. In this embodiment, four foldable arms 1-4 are stretched or bent under the action of corresponding drive motors in the drive device. The drive device 5 includes a drive motor and a mounting housing. In this embodiment, the flexible foldable sail 6 is an important component of the antenna, and the flexible foldable sail 6 is connected to the four foldable arms 1-4 (e.g., bonded). Under the drive of the foldable arms, the flexible foldable sail 6 can deform, causing the antenna surface area to increase or decrease. The flexible foldable sail 6 is preferably circular, with the drive device 5 located at the center. A plurality of foldable arms extend radially from the drive device 5 to the outer periphery of the flexible foldable sail, with one end of each foldable arm connected to the drive device and the other end connected to the edge of the flexible foldable sail. Each folding arm consists of multiple folding units, each with both an unfolded and folded state. The extension and retraction of the folding arm is controlled by a drive mechanism that manages each folding unit, allowing the flexible folding sail to be fully unfolded. Figure 2 ), fully folded state ( Figure 3 ) and partially unfolded state ( Figure 4 Switching between ) and ). The drive unit 5 controls the folding and unfolding of the arm by releasing and retracting the drive rope driven by the motor.

[0022] When the lengths of folding arms 1-4 are all at their maximum L max At that time, the area of ​​the flexible folding sail is at its maximum, which is S. max At this point, the antenna is in a fully deployed state, as shown in Figure 2; when the lengths of the folded arms 1-4 are all at their minimum L... min At that time, the area of ​​the flexible folding sail is minimized to S. min At this point, the antenna is in a fully folded state, as shown in Figure 3; in addition, the length of the folding arms 1-4 can also be set to... That is, the folding arm is located at a certain length between its longest and shortest length, at which point the area of ​​the flexible folding sail surface is S, i.e. .

[0023] During launch and transportation, the antenna structure is in a folded, collapsed state inside the rocket, as shown in Figure 3, occupying minimal space and facilitating launch and transportation. After launch and entry into orbit, it can be unfolded as needed, as shown in the partially unfolded configuration in Figure 4 and the fully unfolded configuration in Figure 2.

[0024] In addition to the planar antennas mentioned above, to achieve high directivity of the antenna—that is, to focus radio waves into a narrow beam in a specific direction, or to receive radio waves from a specific direction—the reusable deployable antenna proposed in this invention can also realize a parabolic antenna configuration, as shown in Figure 6. Figure 7As shown. At this time, all four folding arms 1-4 undergo bending deformation.

[0025] Taking the folding arm 1 as an example, the following details how the folding and unfolding of the folding arm can be achieved through the design of the drive rope.

[0026] like Figure 8 As shown, the folding arm 1 is composed of multiple folding units. Each folding unit has a square support base and a folding section. Each folding section includes two pairs of symmetrically arranged triangular units. One end of each pair of triangles has a rectangular section, which is fixed to the inner and outer sides of one side of the square support base. The other end of the pair of triangles is connected to another pair of triangles via hinges to form a folding unit. Several folding units are arranged in an axial direction, and the long sides of the rectangles are connected to the long sides of the triangles via hinges to form one side of the folding arm. This side is then arranged circumferentially to complete the folding arm 1. That is, each folding unit has four sides, and each side includes a rectangle at the bottom and two symmetrically arranged triangles at the top.

[0027] Each folding arm is equipped with eight unfolding drive ropes and four folding drive ropes, namely the first unfolding drive rope 111, the second unfolding drive rope 112, the third unfolding drive rope 121, the fourth unfolding drive rope 122, the fifth unfolding drive rope 131, the sixth unfolding drive rope 132, the seventh unfolding drive rope 141, and the eighth unfolding drive rope 142; and the first folding drive rope 113, the second folding drive rope 123, the third folding drive rope 133, and the fourth folding drive rope 143. Each side of the folding arm is equipped with two sets of retraction motors, responsible for the retraction and unfolding drives of that side respectively.

[0028] To achieve the transformation of the folding arm 1 from the fully folded state shown in Figure 9 to the fully extended state shown in Figure 8, the combined action of the first extension drive rope 111, the second extension drive rope 112, the third extension drive rope 121, the fourth extension drive rope 122, the fifth extension drive rope 131, the sixth extension drive rope 132, the seventh extension drive rope 141, and the eighth extension drive rope 142 is required. Specifically, as shown in Figure 10 and... Figure 11 The following is an explanation of the main view of the folding arm shown in Figure 11. When the first unfolding drive rope 111, the second unfolding drive rope 112, the fifth unfolding drive rope 131 and the sixth unfolding drive rope 132 shown in Figure 11 are pulled to the right simultaneously under the action of the drive motor, the folding arm 1 will gradually unfold and finally form the fully unfolded state shown in Figure 10.

[0029] Taking one side of the folding arm as an example, each side includes a rectangle at the bottom and two symmetrically arranged triangles at the top. The triangle connected to the rectangle is called the lower triangle, and the triangle symmetrically arranged with the lower triangle is called the upper triangle. The specific routing details of the unfolding drive rope inside the folding arm are shown in Figure 12. All labeled letters are located on the central axis of this example surface. Specifically, A is located near the bottom edge of one end of the lower rectangle; point C is located at the boundary between the triangular and rectangular parts of the lower triangle; B and D are located at the hinge pivots of the lower and upper triangles, respectively (B is on the inside of the folding arm, and D is on the outside); E and F are located near the apex of the triangular part of the lower triangle, respectively (E is on the inside of the folding arm, and F is on the outside). The subscripts 1, 2, and 3 of each letter represent the numbers of each folding unit. Figure 12 In the diagram, folding unit 1 is located at the top, folding unit 2 is located in the middle, and folding unit 3 is located at the bottom. The first unfolding drive rope 111 and the second unfolding drive rope 112 are retracted and shortened under the action of the retracting motor; at the same time, the first folding drive rope 113 is released and extended. As shown in Figure 12(i), the routing of the first unfolding drive rope 111 on the folding arm structure is as follows: The routing of the second deployment drive rope 112 on the folding arm structure is as follows: The end of the first deployment drive rope 111 With folding arm structure The end of the second deployment drive rope 112 is fixed at the point of connection. With folding arm structure The connection is fixed at the point. Under the action of the drive motor, the lengths of both the first deployment drive rope 111 and the second deployment drive rope 112 are shortened, causing the structure to gradually transform from configuration i in Figure 11 to configurations ii and iii, until it is fully deployed. It should be noted that, for the first deployment drive rope 111, its... It was done twice, that is The first time through The point only touches that point and does not move away from it. Passing through the hole a second time Point from It passes through the hole. Therefore, during the deployment of this structure, the first deployment drive rope 111... Section, can be with The point of separation occurs. The configuration shown in Figure 12 (ii) is the critical configuration. After crossing this critical configuration, the first deployment drive rope 111... Duan Yu The point of contact ceases to exist, and separation occurs. When the structure reaches configuration iii, the drive motor is de-energized, and under the action of the structure's elastic force, it finally fully unfolds. As shown in Figure 11, the bistable unit at the top of the folding arm... The bistable unit below remains unchanged. It can be further vertically arrayed downwards to form a series axial array unit. , For the above-mentioned series array structure, the first deployment drive rope 111 and the second deployment drive rope 112 only need to extend downwards, and the wiring method is the same as that of the bistable unit. It remains unchanged.

[0030] For folding drive ropes, the folding of the structures connected to them is achieved by shortening the length of the folding drive rope, such as... Figure 13 As shown. For an array structure composed of each bistable unit connected in series, only one folding drive rope is needed on each side to achieve complete folding of the series array structure.

[0031] The motor at this location retracts the folding drive rope, shortening it, and simultaneously unfolds it to extend it. The routing of the folding drive rope is as follows: The end of the folding drive rope With folding arm structure The structure is fixed at the connection point. Under the action of the drive motor, the length of the folding drive ropes is shortened, causing the structure to gradually transform from configuration i in Figure 13 to configurations ii and iii, until it is fully unfolded. The configuration shown in Figure 13 (ii) is the critical configuration. After passing this critical configuration, the folding drive ropes continue to be shortened to make the structure fully folded, or the drive motor is de-energized and the structure is finally fully folded under the action of elastic force.

[0032] Any process or method described in the flowcharts of this invention or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, achievable on any computer-readable medium for use by an instruction execution system, apparatus, or device. The computer-readable medium can be any medium containing a program for storage, communication, propagation, or transmission for use by an execution system, apparatus, or device, including read-only memory, magnetic disks, or optical disks.

[0033] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, those skilled in the art can combine or combine the different embodiments or examples described in this specification and the features therein without causing contradiction.

[0034] While embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention.

Claims

1. A spatially variable platform that can be repeatedly unfolded, characterized in that, The platform includes a flexible folding sail, several folding arms supporting the sail, and a drive device for moving the arms. The folding arms extend, contract, or bend under the action of corresponding drive motors within the drive device. The flexible folding sail is connected to the arms. The drive device controls the folding of the arms by releasing and retracting drive ropes via motors. Under the drive of the arms, the flexible folding sail deforms, causing the antenna surface area to increase or decrease. When the lengths of the arms are all at their maximum L... max At that time, the area of ​​the flexible folding sail is at its maximum, which is S. max At this point, the antenna is in a fully deployed state; when the lengths of the folded arms are all at their minimum L... min At that time, the area of ​​the flexible folding sail is minimized to S. min At this point, the antenna is in a fully folded state; the length of the folded arm is set to L; where The folding arm is located at a length between its longest and shortest point, at which point the area of ​​the flexible folding sail surface is S. ; The folding arm consists of multiple folding units, each of which has a square support base and a folding section. Each folding section includes two symmetrical, roughly triangular units. Each folding arm is controlled by eight unfolding drive ropes. The first and second deployment drive ropes are shortened by the action of the retraction motor; the routing of the first deployment drive rope on the folding arm structure is as follows: The second deployment drive rope is routed as follows on the folding boom structure: In this diagram, A is located near the bottom edge of the rectangle at one end of the lower triangle; C is located at the boundary between the triangular and rectangular parts of the lower triangle; B and D are located at the hinge pivots of the lower and upper triangles, respectively; E and F are located near the vertex of the triangular part of the lower triangle, respectively. The subscripts 1, 2, and 3 of each letter represent the numbers of each unfolding unit.

2. The repeatedly deployable spatial variable configuration platform according to claim 1, characterized in that, The folding arm comprises multiple folding units. The folding arm is controlled by a drive device that controls each folding unit, allowing the flexible folding sail to switch between a fully deployed state, a fully folded state, and a partially deployed state.

3. The repeatedly deployable spatial variable configuration platform according to claim 2, characterized in that, The flexible folding sail is a circular planar antenna configuration. The driving device is located at the center of the circle. Several folding arms extend radially from the driving device to the outer periphery of the flexible folding sail. One end of the folding arm is connected to the driving device, and the other end is connected to the edge of the flexible folding sail. The antenna folding and unfolding is achieved by controlling the extension and retraction of the folding arms.

4. The repeatedly deployable spatial variable configuration platform according to claim 2, characterized in that, The flexible folding sail is a parabolic antenna configuration. The driving device is located at the bottom of the parabola. Several folding arms extend radially from the driving device to the outer periphery of the flexible folding sail. One end of the folding arm is connected to the driving device, and the other end is connected to the edge of the flexible folding sail. The antenna folding and unfolding is achieved by controlling the bending of the folding arms.

5. A rope-driven system applied to the repeatedly deployable spatial variable-configuration platform according to any one of claims 1-4, characterized in that, Each folding arm is equipped with 8 unfolding drive ropes and 4 folding drive ropes, namely the first unfolding drive rope, the second unfolding drive rope, the third unfolding drive rope, the fourth unfolding drive rope, the fifth unfolding drive rope, the sixth unfolding drive rope, the seventh unfolding drive rope, and the eighth unfolding drive rope; and the first folding drive rope, the second folding drive rope, the third folding drive rope, and the fourth folding drive rope; each side of the folding arm is equipped with two sets of retraction motors, which are responsible for the retraction drive and the unfolding drive of that side, respectively.

6. The rope drive system according to claim 5, characterized in that, The end of the first deployment drive rope With folding arm structure Fixed at the end of the second deployment drive rope With folding arm structure The connection is fixed at the point; under the action of the drive motor, the lengths of both the first and second deployment drive ropes are shortened, and the folding arm structure goes from a fully folded state to a fully deployed state.

7. The rope drive system according to claim 6, characterized in that, The first deployment drive rope is in It went through twice, specifically: The first time through The point only touches that point and does not move away from it. Passing through the hole a second time Point from Passing through the hole; during the structure's deployment, the first deployment drive rope... Section, and The point of separation occurs; after crossing the critical configuration, the first deployment drive rope... Duan Yu The point of contact ceases to exist, and separation occurs.

8. The rope drive system according to claim 5, characterized in that, For the folding drive rope, the folding of the structure connected to it is achieved by shrinking the length of the folding drive rope. For the array structure composed of each bistable unit connected in series, only one folding drive rope is needed to achieve the complete folding of the series array structure. The motor at this location is a retracting motor, which retracts the folding drive rope to shorten it.

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