CN115848654B

CN115848654B - Bistable folding and unfolding unit and array system thereof

Info

Publication number: CN115848654B
Application number: CN202310127762.7A
Authority: CN
Inventors: 付康佳; 张翔; 陈小前; 吴雪松; 庹洲慧; 李越; 张永健; 胡明哲
Original assignee: Tsinghua University; National Defense Technology Innovation Institute PLA Academy of Military Science
Current assignee: Tsinghua University; National Defense Technology Innovation Institute PLA Academy of Military Science
Priority date: 2023-02-17
Filing date: 2023-02-17
Publication date: 2023-05-09
Anticipated expiration: 2043-02-17
Also published as: CN115848654A

Abstract

The invention discloses a bistable folding and unfolding unit and an array system thereof, which are applied to space control, wherein the bistable folding and unfolding unit comprises a first indentation plate and a second indentation plate which are symmetrical to each other, and the first indentation plate and the second indentation plate are provided with an adhesive part and a folding part; at the bonding part, the first indentation plate and the second indentation plate are bonded into a whole; the folding part is provided with a crease, and the folding part can be folded and unfolded along the crease, so that the bistable folding unit is provided with an unfolding configuration, a folding configuration and an intermediate transition configuration, wherein the unfolding configuration and the folding configuration are in a stable balanced state, and the balanced state is a state which can be maintained without applying any external force. The folding and unfolding array system has light weight, safety, flexibility and complex environment adaptability, can adapt to complex and changeable external environments, and meets the intelligent, flexible and smart control requirements of special scenes.

Description

Bistable folding and unfolding unit and array system thereof

Technical Field

The invention relates to the technical field of spacecraft and space control, in particular to a bistable folding unit inspired by paper folding and an array system thereof. Can be applied to large-scale planes in a spacecraft such as: solar sails, antennas, reflectors, etc.

Background

Under the traction of space architecture transformation, the space control capability becomes the key development direction in the field of space technology research, and can lay a foundation for effective application and efficiency exertion of the spacecraft. Future space is widely related to the scenes of on-orbit operation, cluster recovery, autonomous detection maintenance and the like. The spacecraft is supplemented, upgraded, reconstructed and newly built by technologies such as docking maintenance, module replacement, on-orbit assembly, fuel supply and the like, and the service is provided for the regeneration and reconstruction of the cluster functions, forms and organizations of the spacecraft.

Spatial manipulation is required to meet the space requirements of soft touch, robustness, dexterity, reusability. On one hand, the restriction of on-orbit contact and space operation to the severe conditions such as relative attitude measurement, relative attitude maintenance and the like of the spacecraft is greatly relieved; on the other hand, the space manipulation capability of complex space targets needs to be expanded, including capturing and manipulating non-cooperative targets and the like. In the field of space control, at present, expert scholars develop related designs, analysis and experimental researches aiming at special docking mechanisms, space mechanical arms, rope nets and the like. The special docking mechanism has high maturity, but the contact mode is single and is only suitable for cooperation targets. Spatial robotic arms such as the united states "rail cars" and the like are capable of achieving a wide range of operation on targets, however, accurate motion planning of rigid steering systems results in significant limitations on non-cooperative target contact, while lacking adequate impact buffering and energy dissipation. Flexible systems such as rope nets are only suitable for disabled spacecraft and space debris, and cannot be directly used for space dexterous control due to certain destructiveness of the flexible systems to targets.

In order to break through the key problem, the invention provides a bistable self-driven folding unit and an array system which are inspired by folding paper. It has two advantages: firstly, compared with an elastic self-restoring structure, the structure needs to be continuously input to realize configuration maintenance, and a multistable structure only needs to provide pulse input, so that the accurate control of movement deformation and the reconfigurable configuration are realized. The multistable structure design can simplify the design of a driver or a motion switch, can improve the utilization rate of input energy, and the combination of the multistable structure and intelligent driving materials provides a brand new solution for the design of the driver. Secondly, the multistable structure of the invention can effectively prolong the duration of collision and reduce the peak value of collision force, realize controllable momentum transfer and flexible contact with robustness, and greatly reduce the requirements of the structure and a control system.

The existing flexible control devices mostly belong to elastic self-recovery structures, and are mainly characterized in that continuous energy input is needed to maintain the configuration. For example, for an air-driven mechanical arm, deformation such as elongation or bending of the mechanical arm is realized by changing the pressure in the air cavity so as to overcome the elastic deformation of the structure, and once the maintenance of the air pressure is cancelled, the mechanical arm is restored to an initial zero-stress state, so that the maintenance of the configuration under zero input cannot be realized.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention aims to provide a bistable self-driven folding unit inspired by paper folding and an array system thereof, which can realize safe, flexible and self-adaptive operation with a target by utilizing the structural deformation of a programmable soft machine and improve the control capability of the non-cooperative target. The programmable multistable folding array system has the advantages of light weight, safety, flexibility and complex environment adaptability, can adapt to complex and changeable external environments, and meets the intelligent, flexible and smart control requirements of special scenes.

In order to achieve the above-mentioned purpose, the present invention provides a bistable folding unit, which is applied to space control, wherein the bistable folding unit includes a first indentation plate and a second indentation plate which are symmetrical to each other, and an adhesive part and a folding part are arranged on the first indentation plate and the second indentation plate; at the bonding part, the first indentation plate and the second indentation plate are bonded into a whole; the folding part is provided with a crease, the folding part can be folded and unfolded along the crease, so that the bistable folding unit is provided with an unfolding configuration, a folding configuration and an intermediate transition configuration, wherein the unfolding configuration and the folding configuration are in a stable balanced state, the balanced state is a state which can be maintained without applying any external force, the elastic potential energy of the bistable folding unit is increased and then reduced in the process of mutual transition from the folding configuration to the unfolding configuration, and the elastic potential energy of the bistable folding unit is minimum in the unfolding state and the folding state.

Further, the materials, thicknesses and sizes of the first indentation plate and the second indentation plate are the same as those of crease positions, the first indentation plate and the second indentation plate are of rectangular structures ABCD, crease of the first indentation plate is PQ, crease of the second indentation plate is MN, lower end areas of the first indentation plate and the second indentation plate are adhered into a whole to form an adhesion part, the adhesion part is a rectangular area CDST, and the first indentation plate and the second indentation plate have common top crease AB; the bistable folded cell has a width ab=cd=w, ad=bc=l when fully unfolded, where ap=am=bq=bn=a, ps=ms=qt=nt=b, sd=tc=c, the above dimensions satisfying a+b+c=l.

Further, the upper end and the lower end of the unfolding configuration apply a pressure along the vertical direction respectively, and the folding unit is continuously compressed along with the application of an external force, and the rectangular area ABQP and the rectangular area ABNM are folded between the rectangular PQTS and the rectangular MNTS respectively, so that the folding unit is changed from the unfolding configuration to the fully folding configuration through the intermediate transition configuration.

Further, to achieve complete unfolding and folding of the bistable folding unit, it is geometrically necessary to ensure

（1）。

Further, in order to realize the mechanical regulation and control of the bistable folding and unfolding unit, the folding and unfolding unit is subjected to mechanical abstraction, and a simulation mechanical model is established as follows:

establishing a coordinate system, setting the direction perpendicular to the panel of the folding and unfolding unit as an X axis, setting the extending direction of the panel along the crease as a Y axis, and setting the direction perpendicular to the crease on the panel plane as a Z axis; applying a displacement drive on crease AB in the negative Z-axis direction, which displacement drive can be described by a STEP function

（2）

wherein ,

the method comprises the steps of carrying out a first treatment on the surface of the Simulating the transition process of the two-span model from the unfolded state to the folded state; the bistable folding unit is in a fully unfolded configuration, and the crease AB gradually descends in height along with the time, so that the areas PQTS and MNTS are subjected to bending deformation; when the bistable folding and unfolding unit is in a critical switching configuration, the rectangular ABQP and the rectangular AMNB are coplanar, and after the critical switching configuration is exceeded, the bistable folding and unfolding unit is in a complete folding configuration, and the peak external force in a displacement control mode is in direct proportion to the bending rigidity of the indentation plate;

the current moment in the process of carrying out the simulation is the current moment; />

The moment at which the drive for the applied displacement begins to act; />

The moment of ending the action for the applied displacement drive; />

Driving the displacement of the fold AB at the start of action for the applied displacement; />

The displacement of the fold AB at the end of the action is driven for the applied displacement.

Further, the bistable folding and unfolding unit adopts a rope drive and air drive mixed driving mode, so that the bistable unit is folded or unfolded, an inflatable and air-extracting air bag is arranged between the first indentation plate and the second indentation plate, a driving rope penetrates through the first indentation plate and the second indentation plate, one end point of the driving rope is fixed on the folding part, and the other end of the driving rope is connected to the motor, so that the folding or releasing of the driving rope is controlled; under the common cooperation of the driving rope and the air bag, the bistable folding and unfolding unit is folded or unfolded.

In another aspect, the present invention provides a folding and unfolding array system, where the folding and unfolding array system is formed by periodically arranging a plurality of bistable folding and unfolding units along an axial direction; the first indentation plates of the plurality of folding units are integrally formed, and the second indentation plates of the plurality of folding units are integrally formed; a plurality of folds AB and PQ are periodically arranged on the first panel, a plurality of folds AB and MN are periodically arranged on the second panel, the folds AB and the bottom edges CD of two adjacent bistable folding units are integrated, the folding array system has a fully unfolded configuration, a fully folded configuration and a partially folded configuration, and can be converted between different configurations under the action of a driving device.

On the other hand, the invention also provides a folding and unfolding array system which is formed by arranging a plurality of bistable folding and unfolding units along the axial direction and the circumferential direction; based on the axial array, the structural array is further carried out along the circumferential direction, the folding array system has a fully unfolded configuration, a fully folded configuration and a partially folded configuration, and can realize the conversion between different configurations under the action of a driving device, wherein the number of the circumferential arrays is M, the number of the axial arrays is N, and the number of the circumferential arrays is N

Number of axial arrays->

。

Further, in order to prevent geometric interference of the structure in the folding deformation process, the first indentation plate and the second indentation plate are cut; so that it has a minimum width at folds PQ and MN, i.e. PQ in size<AB,PQ<CD, cutting angle ABN' is at

The angle of the clipping angle STN' is +.>

The structure does not interfere and requires two cutting angles +.>

and />

Satisfy the following requirements

（3）。

Further, the folded array system is applied to spacecraft space manipulation equipment.

The multistable folding array system provided by the invention has the advantages that as the system is provided with a plurality of unable stable states, namely a plurality of minimum elastic potential energy values of the system, when the system transits from one stable state to another stable state, energy input is only needed in the transition process, and after the system completes steady state switching, no extra energy is needed to maintain the steady state. Therefore, the multistable structure only needs to provide pulse input when different stable states are switched, and long-time energy input is not needed to maintain a stable state configuration. In addition, as the steady state has stronger robustness, the configuration control precision of the multistable folded array system can be improved.

The multistable folding array system provided by the invention has the advantages of two aspects: firstly, compared with an elastic self-restoring structure, the structure needs to be continuously input to realize configuration maintenance, and a multistable structure only needs to provide pulse input, so that the accurate control of movement deformation and the reconfigurable configuration are realized. The multistable structure design can simplify the design of a driver or a motion switch, can improve the utilization rate of input energy, and the combination of the multistable structure and intelligent driving materials provides a brand new solution for the design of the driver. Secondly, the multistable structure of the invention can effectively prolong the duration of collision and reduce the peak value of collision force, realize controllable momentum transfer and flexible contact with robustness, and greatly reduce the requirements of the structure and a control system.

Drawings

FIG. 1 illustrates a schematic diagram of a deployed steady state configuration of a bi-stable crimping unit in accordance with an embodiment of the present invention;

FIG. 2 illustrates a schematic diagram of a folded stable configuration of a bi-stable folded unit in accordance with an embodiment of the present invention;

FIG. 3 shows a schematic diagram of a multi-body dynamics simulation of a bistable folding unit in an embodiment of the invention;

fig. 4 shows a schematic diagram of the displacement at crease AB of the folding unit of fig. 1 as a function of time;

fig. 5 shows a schematic diagram of the external force displacement of the folding unit in fig. 1 at the crease AB as a function of time;

FIG. 6 shows a displacement versus external force curve for a bellows unit in a displacement control mode;

FIG. 7 shows a schematic representation of an expanded version 1 (panel clipping) of a bistable folding unit;

FIG. 8 shows a schematic representation of an expanded version 2 (perforation) of a bistable folding unit;

FIG. 9 shows a force versus displacement graph for a creased panel at different bending stiffness;

FIG. 10 shows a schematic view of a plurality of folding units in an unfolded state of the axial array system;

FIG. 11 shows a schematic view of a plurality of folding units in a folded state of an axial array system;

fig. 12 shows a schematic diagram of the array system in a fully deployed state (m=4, n=5);

fig. 13 shows a schematic diagram of the array system in a fully folded state (m=4, n=5);

FIG. 14 shows a schematic diagram of the array system's requirements for crease plate cut angles;

FIG. 15 shows a schematic view of the upper three sections of the array system fully extended and the lower two sections fully collapsed;

FIG. 16 is a schematic diagram showing the driving mode of the bistable folding and unfolding unit;

FIG. 17 shows another state schematic of the bistable folding and unfolding unit during driving;

FIG. 18 shows a schematic diagram of the stress and modification during the bistable folding unit driven deployment;

fig. 19 shows a schematic view of the stress and variants during the driving folding of the bistable folding unit.

Detailed Description

The following description of the embodiments of the present invention will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

Specific embodiments of the present invention are described in detail below with reference to fig. 1-19. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

The embodiment of the invention provides a bistable folding unit inspired by folding paper and an array system thereof, which are used for space control of a spacecraft, can greatly relieve the constraint of on-orbit contact and space operation on severe conditions such as relative attitude measurement, relative attitude maintenance and the like of the spacecraft, have high flexibility, and can expand the space control capability under a complex space target state.

In this embodiment, the bistable folding unit inspired by folding paper is formed by bonding two creasing plates at two ends, and its unfolded state and folded state are shown in fig. 1 and 2 respectively. Wherein, the material, thickness, size and crease position of the first creasing plate 1 and the second creasing plate 2 are identical, the crease of the first creasing plate 1 is PQ, and the crease of the second creasing plate 2 is MN. The first indentation plate and the second indentation plate are of rectangular structures, the lower end areas of the first indentation plate and the second indentation plate are adhered into a whole, and the adhered areas are respectively rectangular areas CDST. The first and second creasing plates have a common top crease AB. The bistable folded cell has a width ab=cd=w, ad=bc=l when fully unfolded, where ap=am=bq=bn=a, ps=ms=qt=nt=b, sd=tc=c, the dimensions satisfying a+b+c=l.

At the upper and lower ends of the deployed configuration shown in fig. 1, a pressure in the vertical direction is applied, respectively. With the application of an external force, the unit is continually compressed and the final unfolded configuration is as shown in fig. 2, at which time the unit is fully folded. When fully folded, rectangular areas ABQP and ABNM are folded between rectangular PQTS and rectangular MNTS, respectively.

To achieve full deployment and folding of the bistable folding unit, it is geometrically necessary to ensure

（1）

The unit is subjected to mechanical abstraction, a simulation mechanical model shown in figure 3 is established, and the mechanical regulation and control of the bistable folding and unfolding unit are realized. Wherein: rectangular areas ABNM, ABQP, MNTS, PQTS and STCD are respectively modeled by adopting shell units described by a geometric accuracy method in flexible multi-body dynamics, and specific dimensions and material parameters are shown in table 1; crease AB, crease MN, crease PQ are modeled with revolute pair constraints, respectively.

In addition, a displacement drive is applied to crease AB in the negative Z-axis direction, which can be described by the STEP function

（2）

wherein ,

. The transition process of the two-span model from the unfolded state to the folded state is simulated, and the parameters are set as follows: />

，/>

，/>

，/>

. wherein ,/>

Respectively representing the simulation start time and the simulation end time, < ->

And->

The displacements at the start and end of the simulation are represented, respectively.

Table 1 dimensions and material properties of bistable folded cells

As a result of the simulation, as shown in fig. 3, it can be seen that when t=0 s, the bistable folding unit is in the fully unfolded configuration, and the height of the crease AB gradually decreases with the lapse of time, resulting in bending deformation of the areas PQTS and MNTS. When t=22.2 s, the rectangle ABQP and rectangle ambb are coplanar. When t=30.0 s, the bistable folding unit is in a fully folded configuration. The displacement at the crease AB over time during the unfolding to folding process is shown in fig. 4. The curve of the external force acting on the crease AB under the displacement driving is shown in fig. 5. Combine fig. 4 and 5A displacement-external force relationship curve in the displacement control mode can be obtained as shown in fig. 6.

As can be seen from fig. 4-6, in the displacement control mode, time of day

Corresponding to the critical switching configuration, the external force required at this time is exactly 0, the corresponding displacement is +.>

. If the displacement of crease AB ∈>

The unit will automatically spring back to the original fully deployed state upon removal of the external force; if the displacement of crease AB ∈>

The unit will automatically spring back to the final fully folded state upon removal of the external force. When the folding unit is in a critical switching configuration, the rectangular ABQP and the rectangular AMNB on the upper side are in a coplanar state.

From an energy perspective, the elastic potential energy of the unit increases and then decreases during the transition from the folded configuration to the unfolded configuration. The unfolded state and the folded state correspond to two elastic potential energy minima, respectively. Therefore, the unfolded state and the folded state are stable equilibrium states in terms of mechanics, and other intermediate transition states are unbalanced states.

The implementation form of the bistable folding and unfolding unit can be further expanded on the basis of the bistable folding and unfolding unit, as shown in fig. 7-8. Among them, fig. 7 shows that the creasing plate is made to have a minimum width at folds PQ and MN by cutting it.

I.e. in size

Therefore, the bending rigidity of the indentation plate during deformation can be changed, and the regulation and control of the mechanical properties of the bistable folding and unfolding unit are realized; FIG. 8 shows that by making an array of perforations in the indentation plate, the bending stiffness of the indentation plate during deformation can be adjusted as well, thereby achieving mechanical actuation of the bistable folding unitAnd (5) regulating and controlling the performance.

Essentially, the mechanical properties of the bistable folding and unfolding unit are regulated and controlled by changing the bending rigidity of the indentation plate, and the external force-displacement curve under different displacement control modes can be obtained by regulating the bending rigidity of the indentation plate. As shown in fig. 9, the bending stiffness of the indentation plate was respectively selected as the bending stiffness shown in table 1 (noted as stiffness k ₀ ) It can be seen that the bending stiffness of the indentation plate directly influences the trend of the force-displacement curve by a factor of 0.4, 0.7, 1.0. Quantitatively, the peak external forces corresponding to 0.4, 0.7, 1.0 times the bending stiffness are 6.15N, 10.77N, 15.38N, respectively, i.e. the peak external force in displacement control mode is proportional to the bending stiffness of the indentation plate.

As can be seen from fig. 9, the trend of the force-displacement curve of the bistable folding unit described above is uniform regardless of the thickness of the creasing plate. In general, in the displacement control mode of downward compression, the critical switching configuration is set as a critical point, and can be divided into two stages. The first stage is from a fully deployed configuration to a critical switching configuration, and the external force applied by the first stage is pressure; the first stage is to complete critical switching configuration to fully folded configuration, and the external force applied in this stage is pulling force. The peak external force in the displacement control mode is related to and proportional to the bending stiffness of the indentation plate. In order to adjust the peak external force in the displacement control mode, the bending rigidity of the indentation plate can be adjusted. Further, the bending stiffness is related to the thickness, the elastic modulus and other related parameters of the indentation plate, so that the bending stiffness of the indentation plate can be adjusted by adjusting the thickness, the elastic modulus and other related parameters of the indentation plate, and further the adjustment of the peak external force under the bistable unit displacement control mode is realized.

The bistable folded and unfolded unit array is converted into a bistable folded and unfolded array system. A plurality of bistable folding units are periodically arranged to form a multistable folding array system. Each bistable folded cell is stable in both the initial unfolded configuration and the fully folded configuration, so that the multi-layered structure formed by the plurality of arrays of bistable folded cells has a plurality of stable configurations. The initial unfolded configuration is shown in fig. 10 and the final folded configuration is shown in fig. 11. In the folding and unfolding array system, the first indentation plates of the plurality of folding and unfolding units which are arranged periodically are integrally formed, and the second indentation plates of the plurality of folding and unfolding units are integrally formed. In the manufacturing process, first panels capable of manufacturing N first indentation plates and second panels of N second indentation plates are cut according to the size, a plurality of folds AB and PQ are periodically arranged on the first panels, a plurality of folds AB and MN are periodically arranged on the second panels, and folds AB and bottom edges CD of two adjacent bistable folding units are integrated in a folding array system.

Based on the axial arrays, the structural arrays are further arranged along the circumferential direction, so that a folded array system as shown in fig. 12-13 can be constructed, wherein the number of the circumferential arrays m=4, and the number of the axial arrays n=5 in the example. Fig. 12 shows the fully extended state of the folded array system, and fig. 13 shows the fully folded state of the folded array system. Popularization, for the folded array system, the number of the circumferential arrays is required

The number of axial arrays is +.>

。

It is noted that for a folded array system with a number of circumferential arrays M and a number of axial arrays N, the creasing plate needs to be cut as shown in fig. 13 in order to prevent geometrical interference of the structure during folding deformation. Wherein, the two cutting angles can be respectively recorded as

and />

The structure does not interfere and requires two cutting angles (radians) to meet

（3）

For the straight line configuration, the multistable folded array structure can also be partially formedThe segment units are fully unfolded and the partial segment units are fully folded. Fig. 15 shows one of the possible configurations, with the upper three sections fully extended and the lower two sections fully folded. At this point, the structure is still in a stable equilibrium state, i.e. the maintenance of this configuration does not require any application of external forces. Thus, for a folded array system with a number of circumferential arrays M and a number of axial arrays N, a common construction can be made

A steady-state multistable linear configuration.

For the folding and unfolding array systems shown in fig. 12, 13 and 15, the multi-stable structure can be used in the fields of space folding and unfolding arrays, soft contact and the like, can effectively prolong the collision duration time and reduce the collision force peak value, realizes controllable momentum transfer and robust compliant contact, and greatly reduces the requirements of the structure and a control system. For example, the docking mechanism is applied to the docking mechanism of the micro-nano satellite. Because the volume and the quality of the microsatellite are strictly limited, the scheme and the technology of a docking mechanism have larger differences with a large spacecraft, and the light weight integration and the high integration are key requirements for docking the microsatellite. The microsatellite docking technology has very important research value and wide application prospect for on-orbit operation and function expansion. The folding and unfolding array system provided by the invention is applied to a docking mechanism of a micro-nano satellite, is beneficial to realizing docking soft contact with adjustable mechanical properties, and further provides core technical support for tasks such as spacecraft on-orbit assembly, on-orbit maintenance, on-orbit replacement, on-orbit filling and the like.

For the driving device for realizing the motion deformation of the folding and unfolding array, as shown in fig. 16 and 17, the bistable folding and unfolding unit can adopt a rope driving and gas driving mixed driving mode, so that the bistable unit is folded or unfolded. In particular to an implementation structure, an air bag is arranged between a first indentation plate and a second indentation plate

In addition, a driving rope UVM is penetrated between the first indentation plate and the second indentation plate, and one end U point of the driving rope UVM is fixed on the folds of the first indentation plate and the second indentation plateThe folding part, specifically, one end U point of the driving rope is fixed at the center point of the crease AB, and the other end of the driving rope can be connected to the motor, so that the folding or releasing of the driving rope is controlled. The bistable unit is folded or unfolded under the common cooperation of the driving rope and the air bag.

As shown in fig. 18, when the bistable unit needs to be deployed, the airbag is inflated, and at this time, the internal volume of the airbag increases, so that the first indentation plate and the second indentation plate of the bistable unit are continuously expanded. As the inflation process proceeds, the bistable cell transitions from the fully folded configuration to configuration i, critical state configuration ii, and configuration iii. Subsequently, the balloon is deflated, and the balloon volume of the bistable cell begins to shrink under the elastic force of the structure itself, and the cell eventually transitions to a fully deployed configuration. It should be noted that in the "pre-charge-post-discharge" process described above, it is necessary to ensure that the charging process continues until the cell configuration passes beyond the threshold state. If the inflation process continues below the threshold condition, the cell configuration will revert to the fully folded configuration upon deflation of the balloon, failing to achieve a transition to the fully deployed configuration. In addition, during the above-described unwinding, the motor end of the drive rope will always be in a free state, i.e. the drive rope may be passively changed as the structure is unwound. Because the distance between the point A and the point S is continuously increased in the unit unfolding process, the length of the driving rope is also continuously increased along with the progress of the unfolding process.

As shown in fig. 19, when the bistable unit needs to be folded, the drive cord is contracted, and the distance between points a and S of the bistable unit is continuously reduced, the bistable unit is changed from the fully unfolded configuration to the configuration iii, the critical state configuration ii, and the configuration i. Subsequently, the unit eventually transforms into a fully folded configuration under the elastic force of the structure itself. It should be noted that in order to achieve a switch from the fully deployed configuration to the fully folded configuration, it is necessary to ensure that the reeling process continues until the unit configuration passes the critical state. If the rope winding process is not continued to a critical state, the configuration returns to the fully unfolded configuration under the elastic force of the structure of the unit itself, and the transition to the fully unfolded and folded configuration cannot be realized. In addition, no inflation or deflation operation is applied to the airbag during the entire process of the above-described folding, and the airbag is always kept in a state of being in communication with the outside atmosphere. During the folding process, the volume of the air bag follows the change of the unit configuration, and increases and then decreases.

In the folding array, by independently controlling a plurality of folding units, the precise control of the movement deformation of the folding array system can be realized.

The folding and unfolding array system provided by the invention has the advantages of two aspects: firstly, compared with an elastic self-restoring structure, the structure needs to be continuously input to realize configuration maintenance, and the folding and unfolding array system only needs to provide pulse type input, so that the accurate control of movement deformation and the reconfigurable configuration are realized. The multistable structure design can simplify the design of a driver or a motion switch, can improve the utilization rate of input energy, and the combination of the multistable structure and intelligent driving materials provides a brand new solution for the design of the driver. Secondly, the multistable structure of the invention can effectively prolong the duration of collision and reduce the peak value of collision force, realize controllable momentum transfer and flexible contact with robustness, and greatly reduce the requirements of the structure and a control system.

(1) The invention designs a bistable folding unit inspired by paper folding, which is formed by bonding two pieces of indentation paper at two ends, wherein the unfolding state and the folding state of the bistable folding unit are respectively shown in figures 1 and 2. Wherein, the material, thickness, size and crease position of first indentation board and second indentation board are the same completely, and the crease of first indentation board is PQ, and the crease of second indentation board is MN. The lower end areas of the first indentation plate and the second indentation plate are adhered into a whole, and the adhered areas are respectively rectangular areas CDST. The bistable folded cell has a width ab=cd=w, ad=bc=l when fully unfolded, where ap=am=bq=bn=a, ps=ms=qt=nt=b, sd=tc=c, the dimensions satisfying a+b+c=l. At the upper and lower ends of the deployed configuration shown in fig. 1, a pressure in the vertical direction is applied, respectively. With the application of an external force, the unit is continually compressed and the final unfolded configuration is as shown in fig. 2, at which time the unit is fully folded. When fully folded, rectangular region ABQP rectangular region ABNM is folded between rectangular PQTS and rectangular MNTS, respectively. To achieve the complete bistable folding and unfolding unitUnfolding and folding, geometrically required to ensure

。

(2) The unit is mechanically abstracted and a simulated mechanical model is built as shown in fig. 4. Wherein: rectangular areas ABCJ, JCDI, JCKL, IDFG and LKFG are respectively modeled by shell units described by a geometric accuracy method in flexible multi-body dynamics, and specific dimensions and material parameters are shown in table 1; fold CJ, fold DI and fold KL are respectively modeled by revolute pair constraint; further, a displacement drive is applied to the crease AB in the negative Z-axis direction.

(3) The bending rigidity of the indentation plate during deformation can be changed by cutting or tailoring the indentation plate, so that the regulation and control of the mechanical property of the bistable folding and unfolding unit can be realized, for example, the force-displacement curve of the bistable folding and unfolding unit is realized, and the peak force is in direct proportion to the bending rigidity of the indentation plate. FIG. 7 shows that by cutting the indentation plate, the bending stiffness of the indentation plate during deformation can be changed, so that the mechanical property of the bistable folding and unfolding unit can be regulated and controlled; fig. 8 shows that by performing array perforation on the indentation plate, the bending stiffness of the indentation plate during deformation can be adjusted, so that the mechanical property of the bistable folding and unfolding unit can be regulated.

In the description herein, reference to the term "embodiment," "example," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the different embodiments or examples described in this specification and the features therein may be combined or combined by those skilled in the art without creating contradictions.

While embodiments of the present invention have been shown and described, it will be understood that the embodiments are illustrative and not to be construed as limiting the invention, and that various changes, modifications, substitutions and alterations may be made by those skilled in the art without departing from the scope of the invention.

Claims

1. The bistable folding and unfolding unit is applied to space control and is characterized by comprising a first indentation plate and a second indentation plate which are symmetrical to each other, wherein the first indentation plate and the second indentation plate are provided with an adhesive part and a folding part; at the bonding part, the first indentation plate and the second indentation plate are bonded into a whole; the folding part is provided with a crease, the folding part can be folded and unfolded along the crease, so that the bistable folding unit is provided with an unfolding configuration, a folding configuration and an intermediate transition configuration, wherein the unfolding configuration and the folding configuration are in a stable balanced state, the balanced state is a state which can be maintained without applying any external force, the elastic potential energy of the bistable folding unit is increased and then reduced in the process of mutual transition from the folding configuration to the unfolding configuration, and the elastic potential energy of the bistable folding unit is minimum in the unfolding state and the folding state;

the bistable folding and unfolding unit adopts a rope drive and gas drive mixed driving mode, so that the bistable unit is folded or unfolded, an inflatable and air-extracting air bag is arranged between the first indentation plate and the second indentation plate, a driving rope penetrates through the first indentation plate and the second indentation plate, one end point of the driving rope is fixed on the folding part, and the other end of the driving rope is connected to the motor, so that the folding or releasing of the driving rope is controlled; under the common cooperation of the driving rope and the air bag, the bistable folding and unfolding unit is folded or unfolded.

2. The bistable folding unit of claim 1, wherein the first and second creasing plates are of the same material, thickness and size as the crease locations, the first and second creasing plates are of rectangular configuration ABCD, the crease of the first creasing plate is PQ, the crease of the second creasing plate is MN, the lower end regions of the first and second creasing plates are bonded together to form a bonded portion, the bonded portion is a rectangular region CDST, and the first and second creasing plates have a common top crease AB; the bistable folded cell has a width ab=cd=w, ad=bc=l when fully unfolded, where ap=am=bq=bn=a, ps=ms=qt=nt=b, sd=tc=c, the above dimensions satisfying a+b+c=l.

3. A bistable folding unit according to claim 2, wherein the upper and lower ends of the unfolded configuration are respectively applied with a pressure in the vertical direction, and the folding unit is continuously compressed as the external force is applied, and the rectangular areas ABQP and ABNM are respectively folded between the rectangular PQTS and the rectangular MNTS, so that the folding unit is transformed from the unfolded configuration to the fully folded configuration via the intermediate transition configuration.

4. A bistable folding unit according to claim 2 or 3, characterized in that for achieving a complete unfolding and folding of the bistable folding unit, it is geometrically necessary to ensure

（1）。

5. The bistable folding and unfolding unit according to claim 4, characterized in that in order to realize the mechanical regulation and control of the bistable folding and unfolding unit, the folding and unfolding unit is mechanically abstracted, and a simulation mechanical model is established as follows:

（2）

wherein ,

the method comprises the steps of carrying out a first treatment on the surface of the Simulating the transition process of the two-span model from the unfolded state to the folded state; the bistable folding unit is in a fully unfolded configuration, with the crease AB height following timeGradually lowering, and causing bending deformation of the region PQTS and the region MNTS; when the bistable folding and unfolding unit is in a critical switching configuration, the rectangular ABQP and the rectangular AMNB are coplanar, and after the critical switching configuration is exceeded, the bistable folding and unfolding unit is in a complete folding configuration, and the peak external force in a displacement control mode is in direct proportion to the bending rigidity of the indentation plate; />

The moment at which the drive for the applied displacement begins to act; />

The moment of ending the action for the applied displacement drive; />

6. A folding and unfolding array system, characterized in that it is composed of a plurality of bistable folding units according to any one of claims 1 to 5 periodically arranged axially; the first indentation plates of the plurality of folding units are integrally formed, and the second indentation plates of the plurality of folding units are integrally formed; a plurality of folds AB and PQ are periodically arranged on the first panel, a plurality of folds AB and MN are periodically arranged on the second panel, the folds AB and the bottom edges CD of two adjacent bistable folding units are integrated, the folding array system has a fully unfolded configuration, a fully folded configuration and a partially folded configuration, and can be converted between different configurations under the action of a driving device.

7. A folding and unfolding array system, characterized in thatThe folding and unfolding array system is formed by arranging a plurality of bistable folding and unfolding units according to any one of claims 1 to 5 along the axial direction and the circumferential direction; based on the axial array, the structural array is further carried out along the circumferential direction, the folding array system has a fully unfolded configuration, a fully folded configuration and a partially folded configuration, and can realize the conversion between different configurations under the action of a driving device, wherein the number of the circumferential arrays is M, the number of the axial arrays is N, and the number of the circumferential arrays is N

Number of axial arrays->

。

8. The folding and unfolding array system of claim 7, wherein the first indentation plate and the second indentation plate are tailored to prevent geometric interference of the structure during folding and deforming; so that it has a minimum width at folds PQ and MN, i.e. PQ in size<AB,PQ<CD, cutting angle ABN' is at

The angle of the clipping angle STN' is +.>

The structure does not interfere and requires two cutting angles +.>

and />

Satisfy the following requirements

（3）。

9. A folded array system according to claim 7 or 8, wherein the folded array system is applied to a spacecraft space handling device.