Bistable high-load pneumatic driver and design method

Abstract

The invention relates to a bistable high-load pneumatic driver and a design method.The upper end of an air bag is connected with the middle of a top plate, the lower end of the air bag is connected with the middle of a bottom plate, limbs are arranged on the outer side of the air bag in the circumferential direction and arranged between the top plate and the bottom plate, and each limb comprises an upper limb part and a lower limb part which are hinged to the hinged fold line position; the limbs are parallelogram-shaped after being completely unfolded, the upper end of the upper limb part is hinged to a corresponding top plate hinge seat arranged on the lower side of the top plate, and the lower end of the lower limb part is hinged to a corresponding bottom plate hinge seat arranged on the upper side of the bottom plate. According to the invention, during complete extension, the upper limb part and the lower limb part of each limb are in a locked state on the same vertical surface to ensure the axial rigidity between the top plate and the bottom plate, so that the stable state under complete extension is realized, and a relatively large load can be borne, and during complete contraction, the upper limb part and the lower limb part of each limb are in a locked state on the same vertical surface. And the upper limb part and the lower limb part of each limb can be approximately completely folded, so that the stable state under complete contraction is realized.

Description

Technical Field

[0001] The invention relates to the field of soft robots, in particular to a bistable high-load pneumatic driver and a design method thereof. Background Art

[0002] With the rapid development of soft robots and human-computer interaction, the research on pneumatic soft actuators has become more and more in-depth. Compared with traditional rigid robots, pneumatic soft robots have better environmental adaptability and human-computer interaction friendliness. However, most pneumatic soft actuators in the existing technology are made of soft materials. These soft materials usually have a Young's modulus lower than 10MPa. Although they have good tensile properties, they also result in poor load capacity of the actuator.

[0003] With the development of technology, some pneumatic soft actuators based on origami structures have appeared in the prior art. For example, the patent CN109129456B discloses a pneumatic bidirectional bending soft actuator based on origami structure, which includes a restriction layer structure and two deformation layer structures with the same structure, and the deformation layer structure is composed of a number of origami structures with the same structure arranged in a straight line. The origami structure can achieve axial expansion and contraction in two different states through folding and the material's own superelasticity. However, the material used in the actuator is still soft materials such as silicone rubber, natural silicone, and rubber.

[0004] For another example, the patent CN222003513U discloses an origami structure and a pneumatic soft drive, the device comprises a rectangular main body, the main body comprises first, second, third and fourth rectangular faces, and the first, second, third and fourth rectangular faces are sequentially connected and surrounded to form a rectangular space, wherein a first concave fold line and a second concave fold line are respectively arranged on the first rectangular face and the third rectangular face, when the origami structure is inflated, the first rectangular face and the third rectangular face can be respectively unfolded around the first concave fold line and the second concave fold line by gas, until the first rectangular face and the second rectangular face are stretched into a plane, but the origami structure part of the device is still made of flexible material, and in order to improve the load capacity, the device is also provided with rectangular baffle frames, triangular baffle frames and other structures. Summary of the invention

[0005] The purpose of the present invention is to provide a bistable high-load pneumatic drive and a design method. When fully extended, the upper and lower limbs of each limb are in a locked state on the same vertical plane to ensure the axial stiffness between the top plate and the bottom plate, thereby achieving a stable state under full extension and being able to withstand a large load. When the present invention is fully contracted, the upper and lower limbs of each limb can be almost completely folded, thereby achieving a stable state under full contraction.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A bistable high-load pneumatic actuator comprises a top plate, a bottom plate, an airbag and a plurality of limbs, wherein the upper end of the airbag is connected to the middle of the top plate, and the lower end is connected to the middle of the bottom plate, and each limb is arranged on the outside of the airbag and between the top plate and the bottom plate along the circumferential direction, and the limb comprises an upper limb portion and a lower limb portion hinged at a hinge fold line position, the upper end of the upper limb portion is hinged to a corresponding top plate hinge seat arranged on the lower side of the top plate, and the lower end of the lower limb portion is hinged to a corresponding bottom plate hinge seat arranged on the upper side of the bottom plate.

[0008] The top plate is provided with a top plate connecting hole, and the top plate connecting hole and the top plate hinge seat are staggered along the circumferential direction.

[0009] The bottom plate is provided with bottom plate connecting holes, and the bottom plate connecting holes and the bottom plate hinge seats are staggered along the circumferential direction.

[0010] An upper hinge groove is provided at the upper end of the upper limb portion of the limb, and the upper hinge groove is rotatably connected to the corresponding top plate hinge seat through an upper hinge shaft. A lower hinge groove is provided at the lower end of the lower limb portion of the limb, and the lower hinge groove is rotatably connected to the corresponding bottom plate hinge seat through a lower hinge shaft.

[0011] The groove walls on both sides of the upper hinge groove are provided with upper hinge holes for inserting the upper hinge shaft, and the groove walls on both sides of the lower hinge groove are provided with lower hinge holes for inserting the lower hinge shaft.

[0012] An air nozzle is arranged on one side of the airbag, and airbag connecting plates are arranged on the upper end and the lower end of the airbag.

[0013] A design method of a bistable high-load pneumatic actuator comprises the following steps:

[0014] Step 1: Define the various points of the limb when it is fully folded, specifically:

[0015] Assuming that the thickness of the top plate, bottom plate and limbs are all 0, the various points of the limbs in the fully folded state are defined as follows: the corners of the limbs are A1, B1, D1, and E1, and the two ends of the hinge fold line are C1 and F1, respectively. The origin of the coordinate system of the limb in the folded state is O, and this point coincides with the center point of the bottom plate. O, E1, and D1 are on the same straight line, and the intersection of OD1 and A1F1 is G1. In addition, a parallel line is drawn from F1 to A1B1, and the intersection of this parallel line and B1C1 is H1.

[0016] The limb is a parallelogram when fully extended and the acute angle end ∠D1E1F1=λ;

[0017] |A10|=l d ;

[0018] Step 2: Establish the parameter relationship between the distance H between the top plate and the bottom plate and the limbs in the fully extended state:

[0019] H=(b+c)cos(α)=(e+f)cos(α) (1);

[0020] In the above formula (1), |B1C1|=b, |C1D1|=c, |A1F1|=f, |F1E1|=e, a vertical line is drawn upward along A1, and the angle between the vertical line and A1F1 is α;

[0021] Step 3: When the limbs are fully folded and fully unfolded, the torsion angle of the upper limb relative to the lower limb is θ, and ∠C1F1H1=β, then:

[0022] θ = 2β (4);

[0023] Step 4: Determine the constraint equations for the torsion angle θ and the hinge line position:

[0024]

[0025] f cos(α-θ)-l d sin(θ)=e sin(λ) (8);

[0026] In the above formula (5), |A1B1|=a;

[0027] Step 5: Combine equations (1), (4), (5) and (8) to form a set of constraint equations and solve the parameters that determine the position of the limb articulation line, where a, α, θ, H and l are given. d The values ​​of b, c, e, and f are obtained through the constraint equations;

[0028] Step 6: Let the radius of the circumscribed circle of the top plate be r2, the radius of the circumscribed circle of the regular hexagonal opening between the top plate 1 and the bottom plate 2 be r1, the thickness of the top plate, bottom plate and limbs be t, and according to the limb size parameters solved in step 5 and the distance H between the top plate and the bottom plate, establish a model in the software and perform design analysis and assembly.

[0029] The advantages and positive effects of the present invention are:

[0030] 1. When the present invention is fully extended, the upper limb and lower limb of each limb are in a locked state on the same vertical plane to ensure the axial stiffness between the top plate and the bottom plate, thereby achieving a stable state under full extension and being able to withstand a large load. When the present invention is fully contracted, the upper limb and lower limb of each limb can be almost completely folded, thereby achieving a stable state under full contraction.

[0031] 2. The present invention can form a set of constraint equations and complete the parameter design of the limb through geometric analysis, which is convenient for programming and modeling, and also convenient for timely adjustment of relevant parameters as needed during the computer design stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention,

[0033] Figure 2 for Figure 1 Schematic diagram of the top plate structure,

[0034] Figure 3 for Figure 1 Schematic diagram of the bottom plate structure,

[0035] Figure 4 for Figure 1 Schematic diagram of the airbag structure,

[0036] Figure 5 for Figure 1 Schematic diagram of the limb structure in

[0037] Figure 6 This is a schematic diagram of the zero-thickness design of the present invention in a folded state.

[0038] Figure 7 This is a schematic diagram of the zero-thickness design of the present invention in an unfolded state.

[0039] Figure 8 Schematic diagram of the limbs when designing for the present invention.

[0040] Among them, 1 is the top plate, 101 is the top plate hinge seat, 102 is the top plate connecting hole, 2 is the bottom plate, 201 is the bottom plate hinge seat, 202 is the bottom plate connecting hole, 3 is the limbs, 301 is the upper limb part, 302 is the lower limb part, 303 is the lower hinge hole, 304 is the hinge fold line position, 305 is the upper hinge hole, 4 is the airbag, 401 is the air nozzle, and 402 is the airbag connecting plate. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] like Figures 1 to 8 As shown, the present invention comprises a top plate 1, a bottom plate 2, an air bag 4 and a plurality of limbs 3, wherein the upper end of the air bag 4 is connected to the middle of the top plate 1, and the lower end is connected to the middle of the bottom plate 2, and each limb 3 is arranged outside the air bag 4 and between the top plate 1 and the bottom plate 2 along the circumferential direction. Figure 5As shown, the limb 3 includes an upper limb portion 301 and a lower limb portion 302 hinged at a hinge fold line position 304, and the limb 3 is a parallelogram when fully unfolded, the upper end of the upper limb portion 301 is hinged to the corresponding top plate hinge seat 101 arranged on the lower side of the top plate 1, and the lower end of the lower limb portion 302 is hinged to the corresponding bottom plate hinge seat 201 arranged on the upper side of the bottom plate 2. When the present invention is working, the airbag 4 is inflated and deflated to achieve telescopic action, thereby driving the top plate 1 and the bottom plate 2 to move closer or apart, and at the same time, each limb 3 cooperates to unfold or fold, wherein as Figure 7 As shown, when the present invention is fully extended, the upper limb portion 301 and the lower limb portion 302 of each limb 3 are in a locked state in the same vertical plane to ensure the axial stiffness between the top plate 1 and the bottom plate 2, thereby achieving a stable state under full extension and being able to withstand a large load. When the present invention is fully retracted, as shown in FIG. Figure 6 As shown, the upper limb portion 301 and the lower limb portion 302 of each limb 3 can be almost completely folded, thereby achieving a stable state under complete contraction.

[0043] like Figures 1 to 3 As shown, in this embodiment, the top plate 1 is provided with a top plate connection hole 102 for connecting with the equipment structure on the corresponding side, and the top plate connection hole 102 and the top plate hinge seat 101 are staggered along the circumferential direction. The bottom plate 2 is provided with a bottom plate connection hole 202 for connecting with the equipment structure on the corresponding side, and the bottom plate connection hole 202 and the bottom plate hinge seat 201 are staggered along the circumferential direction.

[0044] like Figures 1 to 3 and Figure 5 As shown, in this embodiment, an upper hinge groove is provided at the upper end of the upper limb portion 301 of the limb 3, and the upper hinge groove is rotatably connected to the corresponding top plate hinge seat 101 through an upper hinge shaft, a lower hinge groove is provided at the lower end of the lower limb portion 302 of the limb 3, and the lower hinge groove is rotatably connected to the corresponding bottom plate hinge seat 201 through a lower hinge shaft, upper hinge holes 305 for inserting the upper hinge shaft are provided on both sides of the groove wall of the upper hinge groove, and lower hinge holes 303 for inserting the lower hinge shaft are provided on both sides of the groove wall of the lower hinge groove. In addition, in this embodiment, a hinge shaft can be provided at the hinge fold line position 304 to realize the hinge connection between the upper limb portion 301 and the lower limb portion 302.

[0045] like Figure 4 As shown, in this embodiment, a gas nozzle 401 is provided on one side of the airbag 4 for supplying air, and an airbag connecting plate 402 is provided at the upper end and the lower end of the airbag 4 to be respectively connected to the top plate 1 and the bottom plate 2. In this embodiment, the airbag 4 adopts a Chrislin origami structure, which is a well-known technology in the art. The airbag structure hardly undergoes elastic deformation during the deformation process, and the driving air pressure is low.

[0046] The design method of the present invention mainly determines the hinge fold line position 304, thereby ensuring that the fully unfolded and fully folded states of the limb 3 can meet the bistable requirements of the present invention.

[0047] The design method of the present invention comprises the following steps:

[0048] Step 1: Define the various points of limb 3 in the fully folded state.

[0049] In order to facilitate the design analysis, Figures 6 to 8 As shown, the present invention is designed on the assumption that the thickness of the top plate 1, the bottom plate 2 and the limbs 3 are all 0. In addition, this embodiment includes six identical limbs 3, and the present invention only needs to determine the size of one limb 3.

[0050] like Figure 8 As shown, the various points of the limb 3 in the fully folded state are defined as follows: the corner ends of the limb 3 are A1, B1, D1, and E1, and the two ends of the hinge fold line position 304 are C1 and F1, respectively. When the limb 3 is fully folded, it lies on the bottom plate 2. Since the thickness of the top plate 1, the bottom plate 2, and the limb 3 is 0, the center Ou of the top plate 1, the center Od of the bottom plate 2, and Figure 6 The origin O of the coordinate system of the present invention in the folded state shown in FIG. Figure 8 As shown, in this state, O, E1, and D1 are on the same straight line, the intersection of OD1 and A1F1 is G1, and a parallel line is drawn from F1 as the starting point and parallel to A1B1, and the intersection of the parallel line and B1C1 is H1.

[0051] Step 2: Establish a parameter relationship between the distance H between the top plate 1 and the bottom plate 2 in the fully extended state (ie, the overall height of the present invention) and the limb 3.

[0052] like Figure 8 As shown, assuming |B1C1|=b, |C1D1|=c, |A1F1|=f, |F1E1|=e, draw a vertical line upward along A1, and the angle between the vertical line and A1F1 is α, then according to the geometric relationship:

[0053] H=(b+c)cos(α)=(e+f)cos(α) (1);

[0054] Step 3: Define the torsion angle θ. When the present invention is fully folded to fully unfolded, the torsion angle of the upper limb 301 relative to the lower limb 302 is θ. Figure 8 As shown, let ∠C1F1H1=β, ∠H1F1A1=λ, ∠E1F1G1=λ1, then ∠H1F1E1=λ-λ1, and at the same time ∠E1G1F1=∠A1G1O=λ-λ1

[0055] According to the geometric relationship, ∠A1G1O=∠E1G1F1=∠H1F1E1=λ-λ1. Since the sum of the interior angles of triangle A1G1O is 180°, we have:

[0056] θ+2λ-λ1=π (2);

[0057] And ∠CF1E1′ is the folded ∠C1F1E1, so:

[0058] 2(λ-λ1+β)+λ1=π (3);

[0059] According to the above formulas (2) and (3), we can get:

[0060] θ=2β (4).

[0061] Step 4: Determine the constraint equations of the torsion angle θ and the hinge line position 304 .

[0062] Since A1B1∥F1H1, A1F1∥B1H1, therefore ∠C1H1F1=∠H1B1A1=λ, and |F1H1|=|A1B1|=a, |C1B1|=b, |F1A1|=f, then |C1H1|=bf. In triangle F1H1C1, the sine theorem yields:

[0063]

[0064] Similarly, in triangle OA1G1 and triangle F1E1G1, using the sine theorem we get:

[0065]

[0066] In the above formula (6), |A1O|=l d , |E1F1|=e;

[0067] In triangle OA1G1, the triangle interior angle theorem gives:

[0068]

[0069] Combining equations (6) and (7) and simplifying them, we can get:

[0070] f cos(α-θ)-l d sin(θ)=e sin(λ) (8);

[0071] Step 5: Combine equations (1), (4), (5) and (8) to form a set of constraint equations and solve the parameters for determining the position of the limb hinge line 304, where a, α, θ, H and l are given. d The values ​​of b, c, e, and f are obtained through the constraint equations.

[0072] In this embodiment, MATLAB computer software can be used for calculation.

[0073] Step 6: If Figure 7 As shown, let the radius of the circumscribed circle of the top plate 1 be r2, the radius of the circumscribed circle of the regular hexagonal opening between the top plate 1 and the bottom plate 2 be r1, the thickness of the top plate 1, the bottom plate 2 and the limb 3 be t, and according to the size parameters of the limb 3 solved in step 5 and the distance H between the top plate 1 and the bottom plate 2, establish a model in the SolidWorks 3D software and perform design analysis and assembly.

Claims

1. A bistable high-load pneumatic actuator, characterized in that: The invention comprises a top plate (1), a bottom plate (2), an air bag (4) and a plurality of limbs (3), wherein the upper end of the air bag (4) is connected to the middle part of the top plate (1), and the lower end is connected to the middle part of the bottom plate (2); each limb (3) is arranged on the outside of the air bag (4) and between the top plate (1) and the bottom plate (2) along the circumferential direction; the limb (3) comprises an upper limb part (301) and a lower limb part (302) hinged at a hinge fold line position (304); the upper end of the upper limb part (301) is hinged to a corresponding top plate hinge seat (101) arranged on the lower side of the top plate (1); and the lower end of the lower limb part (302) is hinged to a corresponding bottom plate hinge seat (201) arranged on the upper side of the bottom plate (2).

2. The bistable high-load pneumatic actuator according to claim 1, characterized in that: The top plate (1) is provided with a top plate connecting hole (102), and the top plate connecting hole (102) and the top plate hinge seat (101) are arranged alternately along the circumferential direction.

3. The bistable high-load pneumatic actuator according to claim 1, characterized in that: The bottom plate (2) is provided with a bottom plate connecting hole (202), and the bottom plate connecting hole (202) and the bottom plate hinge seat (201) are arranged alternately along the circumferential direction.

4. The bistable high-load pneumatic actuator according to claim 1, characterized in that: An upper hinge groove is provided at the upper end of the upper limb part (301) of the limb (3), and the upper hinge groove is rotatably connected to the corresponding top plate hinge seat (101) through an upper hinge shaft, and a lower hinge groove is provided at the lower end of the lower limb part (302) of the limb (3), and the lower hinge groove is rotatably connected to the corresponding bottom plate hinge seat (201) through a lower hinge shaft.

5. The bistable high-load pneumatic actuator according to claim 4, characterized in that: The groove walls on both sides of the upper hinge groove are provided with upper hinge holes (305) for inserting the upper hinge shaft, and the groove walls on both sides of the lower hinge groove are provided with lower hinge holes (303) for inserting the lower hinge shaft.

6. The bistable high-load pneumatic actuator according to claim 1, characterized in that: An air nozzle (401) is provided on one side of the airbag (4), and airbag connecting plates (402) are provided on the upper and lower ends of the airbag (4).

7. A method for designing a bistable high-load pneumatic actuator according to claim 1, characterized in that: The steps include: Step 1: Define the various points of the limb (3) in the fully folded state, specifically: Assuming that the thickness of the top plate (1), the bottom plate (2) and the limb (3) are all 0, the various points of the limb (3) in the fully folded state are defined as follows: the corner ends of the limb (3) are A1, B1, D1, and E1, respectively, the two ends of the hinge fold line position (304) are C1 and F1, respectively, the origin of the coordinate system of the limb (3) in the folded state is O, and this point coincides with the center point of the bottom plate (2), O, E1, and D1 are on the same straight line, and the intersection of OD1 and A1F1 is G1, and in addition, a parallel line is drawn from F1 to be parallel to A1B1, and the intersection of this parallel line and B1C1 is H1; The limb (3) is a parallelogram when fully extended and the acute angle end ∠D1E1F1=λ; ∣A10∣＝l d ； Step 2: Establish the parameter relationship between the distance H between the top plate (1) and the bottom plate (2) in the fully extended state and the limb (3): H=(b+c)cos(α)=(e+f)cos(α) (1); In the above formula (1), |B1C1|=b, |C1D1|=c, |A1F1|=f, |F1E1|=e, a vertical line is drawn upward along A1, and the angle between the vertical line and A1F1 is α; Step 3: When the limb (3) is fully folded and fully unfolded, the twisting angle of the upper limb (301) relative to the lower limb (302) is θ, and ∠C1F1H1=β, then: θ = 2β (4); Step 4: Determine the constraint equations of the torsion angle θ and the hinge line position (304): fcos(α-θ)-l d sin(θ)=esin(λ) (8); In the above formula (5), |A1B1|=a; Step 5: Combine equations (1), (4), (5) and (8) to form a set of constraint equations and solve the parameters for determining the position of the limb hinge line (304), where a, α, θ, H and l are given. d The values ​​of b, c, e, and f are obtained through the constraint equations; Step 6: Let the radius of the circumscribed circle of the top plate (1) be r2, the radius of the circumscribed circle of the regular hexagonal opening between the top plate 1 and the bottom plate 2 be r1, the thickness of the top plate (1), the bottom plate (2) and the limb (3) be t, and according to the size parameters of the limb (3) solved in step 5 and the distance H between the top plate (1) and the bottom plate (2), establish a model in the software and perform design analysis and assembly.

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