Bistable high-load pneumatic actuator and design method

Abstract

The application relates to a bistable high-load pneumatic driver and a design method, wherein the upper end of a gas bag is connected with the middle part of a top plate, the lower end is connected with the middle part of a bottom plate, each limb is arranged outside the gas bag along a circumferential direction and between the top plate and the bottom plate, the limb comprises an upper limb part and a lower limb part which are hinged at a hinged fold line position, the limb is a parallelogram after being completely unfolded, the upper end of the upper limb part is hinged with 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 with a corresponding bottom plate hinge seat arranged on the upper side of the bottom plate. When the application is completely stretched, the upper limb part and the lower limb part of each limb are in the same vertical locking state to ensure the axial rigidity between the top plate and the bottom plate, so that the stable state under complete stretching is realized, and a larger load can be borne; when the application is completely contracted, 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 present application relates to the field of soft robots, in particular to a bistable high-load pneumatic driver and design method. BACKGROUND

[0002] With the rapid development of soft robots and human-computer interaction fields, the research on pneumatic soft drivers is also more and more in-depth. Compared with traditional rigid robots, pneumatic soft robots have better environmental adaptability and human-computer interaction friendliness, but most of the existing pneumatic soft drivers are made of soft materials, which have a Young's modulus lower than 10 MPa. Although these soft materials have good tensile properties, they also result in poor load capacity of the driver.

[0003] With the development of technology, some pneumatic soft drivers based on origami structure have appeared in the prior art. For example, the patent CN109129456B discloses a pneumatic bidirectional bending soft driver based on origami structure, which includes a restriction layer structure and two structure-same deformation layer structures, and the deformation layer structure is composed of a plurality of straightly arranged structure-same origami structures. The origami structure can realize axial stretching and contraction of two different states through folding and unfolding and the material itself super-elasticity. However, the material used in this driver is still soft material such as silicone rubber, natural silica gel and rubber.

[0004] For another example, the patent CN222003513U discloses an origami structure and a pneumatic soft driver. The device includes a rectangular main body, which includes first, second, third and fourth rectangular surfaces, and the first, second, third and fourth rectangular surfaces are sequentially connected to form a rectangular space. First and third rectangular surfaces are respectively provided with first and second concave folding lines. When the origami structure is inflated, the first and third rectangular surfaces can be unfolded around the first and second concave folding lines by gas, until the first and second rectangular surfaces are stretched into a plane. However, the origami structure part of this device is still made of flexible material, and in order to improve the load capacity, the device is also provided with rectangular blocking frame, triangular blocking frame and other structures. SUMMARY

[0005] The purpose of the present application is to provide a bistable high-load pneumatic driver and design method. When fully stretched, the upper limb part and the lower limb part of each limb are in the same vertical locking state to ensure the axial stiffness between the top plate and the bottom plate, so as to realize the stable state under full stretching, and can bear larger load. When the present application is fully contracted, the upper limb part and the lower limb part of each limb can be approximately completely folded, so as to realize the stable state under full contraction.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A bistable high-load pneumatic driver, comprising a top plate, a bottom plate, an air bag and a plurality of limbs, wherein the upper end of the air bag is connected to the middle of the top plate and the lower end is connected to the middle of the bottom plate, each limb is arranged outside the air bag along the circumferential direction and between the top plate and the bottom plate, the limb comprises an upper limb part and a lower limb part hinged at a hinged fold line position, 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.

[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 a bottom plate connecting hole, and the bottom plate connecting hole and the bottom plate hinge seat are staggered along the circumferential direction.

[0010] The upper end of the upper limb part of the limb is provided with an upper hinge groove, and the upper hinge groove is rotationally connected to the corresponding top plate hinge seat through an upper hinge shaft, and the lower end of the lower limb part of the limb is provided with a lower hinge groove, and the lower hinge groove is rotationally 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] One side of the air bag is provided with an air nozzle, and the upper end and the lower end of the air bag are each provided with an air bag connecting plate.

[0013] A design method according to the bistable high-load pneumatic driver, comprising the following steps:

[0014] Step 1: define each point position of the limb in the fully folded state, specifically:

[0015] Assuming that the thicknesses of the top plate, the bottom plate and the limb are all 0, the definition of each point position of the limb in the fully folded state is as follows: each corner end of the limb is A1, B1, D1 and E1 respectively, the two ends of the hinged fold line position are C1 and F1 respectively, the origin of the coordinate system in the folded state of the limb is O, which 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, and a parallel line is drawn from F1 parallel to A1B1, and the intersection of the parallel line and B1C1 is H1.

[0016] The limb is a parallelogram after being fully unfolded and the acute angle ∠D1E1F1 = λ.

[0017] |A10| = l d ;

[0018] Step two: establish the relationship between the distance H between the top plate and the bottom plate in the fully extended state and the parameters of the limb:

[0019] H=(b+c)cos(alpha)=(e+f)cos(alpha) (1);

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

[0021] Step three: let the torsion angle of the upper limb part relative to the lower limb part of the limb be theta when the limb is fully folded to fully unfolded, and let ∠C1F1H1=beta, then:

[0022] theta=2beta (4);

[0023] Step four: determine the constraint equation of the torsion angle theta and the hinge fold line position:

[0024]

[0025] f cos(alpha-theta)-l d sin(theta)=esin(lambda) (8);

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

[0027] Step five: the above formulas (1), (4), (5) and (8) are combined to form a constraint equation group and the parameters determining the hinge fold line position of the limb are solved, wherein the values of a, alpha, theta, H and l d are given, and b, c, e, f are obtained through the constraint equation;

[0028] Step six: let the radius of the circumscribed circle of the top plate be r2, the radius of the circumscribed circle of the hexagonal hole in the top plate 1 and the bottom plate 2 be r1, and the thickness of the top plate, the bottom plate and the limb be t, and the model is established in the software according to the limb size parameters and the distance H between the top plate and the bottom plate solved in step five, and design analysis and assembly are carried out.

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

[0030] 1. In the fully extended state, the upper limb part and the lower limb part of each limb are in the same vertical locking state to ensure the axial stiffness between the top plate and the bottom plate, so as to realize the stable state under full extension, and can bear larger load, and when the present application is fully contracted, the upper limb part and the lower limb part of each limb can be approximately fully folded, so as to realize the stable state under full contraction.

[0031] 2. The present invention can construct 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 limb structure,

[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 includes a top plate 1, a bottom plate 2, an airbag 4 and a plurality of limbs 3, wherein the upper end of the airbag 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 airbag 4 along the circumferential direction and between the top plate 1 and the bottom plate 2. 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 provided 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 provided 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 movement, 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 shown in FIG. 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 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 top plate connection holes 102 for connecting to the equipment structure on the corresponding side, and the top plate connection holes 102 and the top plate hinge seat 101 are staggered along the circumferential direction. The bottom plate 2 is provided with bottom plate connection holes 202 for connecting to the equipment structure on the corresponding side, and the bottom plate connection holes 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, the upper end of the upper limb portion 301 of the limb 3 is provided with an upper hinge groove, and the upper hinge groove is rotatably connected to the corresponding top plate hinge seat 101 via an upper hinge shaft. The lower end of the lower limb portion 302 of the limb 3 is provided with a lower hinge groove, and the lower hinge groove is rotatably connected to the corresponding bottom plate hinge seat 201 via a lower hinge shaft. 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. In addition, in this embodiment, a hinge shaft can be provided at the hinge fold line position 304 to achieve the hinge connection between the upper limb portion 301 and the lower limb portion 302.

[0045] like Figure 4 As shown, in this embodiment, the airbag 4 is provided with an air nozzle 401 on one side for air supply. Airbag connecting plates 402 are provided at both the top and bottom ends of the airbag 4, connecting to the top plate 1 and bottom plate 2, respectively. In this embodiment, the airbag 4 utilizes a Crislin origami structure, a well-known technique in the art. This airbag structure exhibits little elastic deformation during deformation, resulting in low driving pressure.

[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 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, bottom plate 2 and limb 3 is 0, the center Ou of the top plate 1 and the center Od of the bottom plate 2 are Figure 6 The coordinate system origin O 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 to A1B1, and the intersection of this 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 (i.e., 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 twisting angle θ. When the present invention is fully folded to fully unfolded, the twisting 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, and according to the sum of the internal angles of the triangle A1G1O is 180°, then:

[0056] θ + 2λ - λ1 = π (2);

[0057] And ∠CF1E1' is the folded ∠C1F1E1, thus:

[0058] 2(λ - λ1 + β) + λ1 = π (3);

[0059] According to the above formula (2) and (3), we have:

[0060] θ = 2β (4).

[0061] Step four: determine the constraint equation of the twist angle θ and the hinge fold line position 304.

[0062] Since A1B1∥F1H1, A1F1∥B1H1, thus ∠C1H1F1 = ∠H1B1A1 = λ, and |F1H1| = |A1B1| = a, |C1B1| = b, |F1A1| = f, then |C1H1| = b - f, in the triangle F1H1C1, by the sine theorem, we have:

[0063]

[0064] Similarly, in the triangle OA1G1 and the triangle F1E1G1, by the sine theorem, we have:

[0065]

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

[0067] In the triangle OA1G1, by the theorem of the sum of the internal angles of a triangle, we have:

[0068]

[0069] By combining the above formula (6) and (7) and simplifying, we have:

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

[0071] Step five: combine the above formula (1), (4), (5) and (8) to form a constraint equation set and solve the parameters of the limb hinge fold line position 304, wherein the values of a, α, θ, H and l d are given, and b, c, e, f are obtained by the constraint equation.

[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 method of designing a bi-stable high load pneumatic actuator, characterized by: The bistable high-load pneumatic driver 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), the lower end is connected to the middle of the bottom plate (2), each limb (3) is arranged outside the air bag (4) along the circumferential direction and between the top plate (1) and the bottom plate (2), the limb (3) comprises an upper limb part (301) and a lower limb part (302) hinged at a hinged 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). The design method of the bistable high-load pneumatic driver comprises the following steps: Step one: define each point of the limb (3) in the fully folded state, specifically: Assuming that the thicknesses of the top plate (1), the bottom plate (2) and the limb (3) are all 0, each point of the limb (3) in the fully folded state is defined as follows: each corner end of the limb (3) is A1, B1, D1 and E1 respectively, the two ends of the hinged 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, which 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 a parallel line is drawn from F1 parallel to A1B1, and the intersection of the parallel line and B1C1 is H1; The limb (3) is a parallelogram after being fully unfolded, and the acute angle ∠D1E1F1 = λ; | A10 | = 1 d ; Step two: establish the parameter relationship between the distance H between the top plate (1) and the bottom plate (2) and the limb (3) in the fully extended state: H = (b + c)cos(α) = (e + f)cos(α) (1); In the above formula (1), |B1C1| = b, |C1D1| = c, |A1F1| = f, |F1E1| = e, a perpendicular line is drawn along A1 upwards, and the included angle between the perpendicular line and A1F1 is α; Step three: let the twist angle of the upper limb part (301) relative to the lower limb part (302) of the limb (3) be θ when the limb (3) is fully folded to fully unfolded, and let ∠C1F1H1 = β, then: θ = 2β (4); Step four: determine the constraint equation of the twist angle θ and the hinged fold line position (304): f cos(a - Q) - 1 d sin(0) = e sin(A) (8) In the above formula (5), |A1B1| = a; Step five: the above formula (1), (4), (5) and (8) constitute a constraint equation set and solve the parameters of the limb hinge fold line position (304), wherein the values of a, α, θ, H and l are given, and b, c, e and f are obtained by the constraint equation set d . Step six: let the radius of the circumscribed circle of the top plate (1) be r2, the radius of the circumscribed circle of the hexagonal opening between the top plate (1) and the bottom plate (2) be r1, the thicknesses of the top plate (1), the bottom plate (2) and the limb (3) be t, and the limb (3) size parameters and the distance H between the top plate (1) and the bottom plate (2) obtained in step five are used to establish a model in software for design analysis and assembly.

2. The design method of a 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 staggered along the circumferential direction.

3. The design method of a 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 staggered in the circumferential direction.

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

5. The method of designing a bi-stable high load pneumatic actuator according to claim 4, characterized in that: The two side groove walls of the upper hinge groove are provided with upper hinge holes (305) for inserting the upper hinge shaft; the two side groove walls of the lower hinge groove are provided with lower hinge holes (303) for inserting the lower hinge shaft.

6. The method of designing a bi-stable high load pneumatic actuator as claimed in claim 1, wherein: One side of the air bag (4) is provided with an air nozzle (401), and the upper end and the lower end of the air bag (4) are provided with air bag connecting plates (402).

Images