Soft manipulator for picking famous high-quality tea and accurate clamping force modeling method

Abstract

The invention relates to agricultural machinery, in particular to a famous high-quality tea picking soft manipulator and a clamping force accurate modeling method. According to the famous high-quality tea picking soft manipulator and the accurate clamping force modeling method, the soft manipulator can achieve accurate regulation and control over the clamping force, and therefore high-quality tea leaf raw materials are obtained. According to the technical scheme, the famous high-quality tea picking soft manipulator is characterized by comprising a base, two fingers, a power source and two driving ropes, wherein the two fingers are symmetrically and vertically fixed to the base and are of the same structure, the power source is installed on the base and located between the two fingers, and the two driving ropes are located on the opposite sides of the two fingers respectively; each finger comprises an integral flexible beam, a far phalanx and a near phalanx; the integral flexible beam is vertically arranged; the rear end of the integral flexible beam is fixed on the base; the far phalanx is fixed at the front end of the integral flexible beam; one end of the driving rope is connected with the far phalanx, and the other end of the driving rope sequentially penetrates through the near phalanx and the base upwards and then is connected with the power source.

Description

Technical Field

[0001] The present invention relates to an agricultural machine, in particular to a high-quality tea picking soft manipulator and a method for accurately modeling the clamping force. Background Technique

[0002] At present, the methods for picking high-quality tea can be divided into blade cutting and human-like "lifting" picking methods. For the blade cutting method, such as a tube-internal shearing tea picking device described in CN111903329B, which includes a shearing mechanism for cutting tea stalks, a collecting mechanism for collecting the cut-stalk tea leaves, a side-bending mechanism for adjusting the working direction of the shearing mechanism, a parallel mechanism for driving the shearing mechanism to lift, and a controller electrically connected to the above mechanisms. However, this method will damage the appearance of the tea leaves, and the cut of the tea stalk will quickly turn black after being oxidized by the air. For the human-like "lifting" picking method, such as a single-bud tea picking manipulator based on soft drive described in CN111136678B, which includes a frame, a clamping jaw arranged in the frame, a motor for driving the clamping jaw to rotate, a pneumatic mechanism for driving the clamping jaw to open and close, a sensor, a collecting box, and a controller. At present, almost all of the "lifting" type picking manipulators adopt pneumatic drive methods and need to carry a gas pump negative pressure device, which will increase the complexity of agricultural robots. In addition, when picking tea buds, the magnitude of the clamping force applied by the manipulator is very important. When the clamping force is small, the tea buds are likely to slip, and when the clamping force is large, the tea buds will be damaged. However, the existing picking manipulators have not analyzed the clamping force. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above background technique and provide a high-quality tea picking soft manipulator and a method for accurately modeling the clamping force. The soft manipulator can achieve precise control of the clamping force, so as to obtain high-quality tea raw materials.

[0004] The technical solution provided by the present invention is:

[0005] A high-quality tea picking soft manipulator, characterized in that: the soft manipulator includes a base, two fingers symmetrically and vertically fixed on the base and having the same structure, a power source installed on the base and located between the two fingers, and two drive ropes respectively located on the opposite sides of the two fingers; each finger includes an integral flexible beam arranged vertically and fixed at the rear end to the base, a distal phalanx fixed at the front end of the integral flexible beam, and a proximal phalanx fixed at the middle part of the integral flexible beam. One end of the drive rope is connected to the distal phalanx, and the other end passes through the proximal phalanx and the base upward in sequence and then is connected to the power source.

[0006] The driving rope extends along the length direction of the integral flexible beam, is located on the symmetric plane in the width direction (to avoid distortion caused by eccentric loading), and has a preset spacing from the surface of the flexible beam to form a bending force arm structure, so as to apply a bending moment to the flexible beam when the driving rope is tensioned, causing it to generate a directional bending deformation, thereby enabling the fingertips of the two fingers to contact and generate a clamping force.

[0007] Silica gel is fixed on the distal phalanges of the two fingers, and the two pieces of silica gel are arranged facing each other to avoid damage to the tea leaves during picking.

[0008] The power source is a servo electric cylinder; a through hole for the push rod of the servo electric cylinder to pass through is provided on the base.

[0009] Holes for the driving rope to pass through and be guided are respectively provided at the corresponding positions of the base and the proximal phalanx.

[0010] The soft manipulator is fixed on the rotating shaft of the joint motor through a connecting plate and a motor mounting plate connected in sequence; the connecting plate and the motor mounting plate are in an inclined "L" shape, and the angles between them are coordinated so that the initial state of the soft manipulator is vertically downward and the collecting state is inclined, so as to facilitate the tea buds to fall into the collecting box under the action of gravity.

[0011] A precise modeling method for the clamping force of a soft manipulator for picking famous and high-quality tea is carried out according to the following steps:

[0012] 1. Segmentation of the integral flexible beam

[0013] As Figure 15 shown, the integral flexible beam is successively divided into four segments along its length direction from the fixed end (point A): the first segment (from point A to point B), the second segment (from point B to point C), the third segment (from point C to point D), and the fourth segment (from point D to point G). Among them, the first segment and the third segment are the first free deformation segment and the second free deformation segment respectively, and are analyzed using the chained beam constraint model; the second segment and the fourth segment are the first constraint segment and the second constraint segment respectively, keep a straight state, only transfer loads and do not participate in the bending analysis. Coordinate systems XAY and XCY are respectively established at the leftmost segments of the first segment and the third segment.

[0014] 2. Determine the force and moment parameters at the free ends of the third segment and the first segment

[0015] Both the third segment and the first segment are discretized into N equal-length units, the unit length is L / N, and N + 1 nodes (numbered 0 to N) are obtained. Local coordinate systems x i o i y i (0 ≤ i ≤ N) are established at each node, and the force and moment parameters from the free end to the starting end of each free deformation segment (from the local coordinate system x N o N y Nto x 0 o 0 y 0 homogeneous transformation matrix of 0 T N :

[0016]

[0017] where α i represents the normalized rotation angle of each unit.

[0018] According to the force translation theorem, the rope tension F t and the clamping force F s can be translated to the free end of the third segment and transmitted to the first segment step by step through the second segment. Therefore, first analyze the forces and moments at the free end of the third segment, and then deduce the force and moment parameters at the free end of the first segment.

[0019] ① Force and moment parameters at the free end of the third segment

[0020] For the third segment, point D is equivalent to the free end, and point C is equivalent to the fixed end. According to the above formula, the homogeneous transformation matrix C T D from point D to point C can be constructed. Through this homogeneous transformation matrix, the coordinates of points P 3 , P 4 and D in the XCY coordinate system can be expressed.

[0021] The angle θ 4 between the direction of the driving rope tension P 3 P 4 and the vector P 4 D is:

[0022]

[0023] Similarly, the angles θ 2 and θ 3 can also be calculated in the same way.

[0024] As Figure 17 shown, the rope tension F t and the clamping force F s can be translated and decomposed to the free end (point D) of the third segment, obtaining the axial force C F D,x , the lateral force C F D,y and the moment C M D (The horizontal coordinate, vertical coordinate and rotation angle of the free end after deformation are respectively C X D , C Y D andC θ D ), these forces and the normal force F n are transmitted and decomposed to the free end (point B) of the first segment together, obtaining the axial force A F B,x , the lateral force A F B,y and the moment A M B (the horizontal coordinate, vertical coordinate and rotation angle of the free end after deformation are A X B , A Y B and A θ B ). It should be noted that the positive directions of the forces and moments described in the present invention are subject to the directions indicated by the arrows in the drawings and have nothing to do with the positive directions of the coordinate system. The decomposition direction of the force is determined by projecting along the original force direction shown in the figure, and the positive direction of the moment is subject to the rotation direction indicated by the curved arrow in the figure. For the rope tension F t and the clamping force F s , translate and decompose (based on the XCY coordinate system of this segment) to the free end (point D) of the third segment, obtaining the following force and moment parameters:

[0025]

[0026] where W 1 represents the vertical distance between the driving rope and the integral flexible beam, and θ Ft represents the angle between the direction of the driving rope tension and the negative y-axis of the XCY coordinate system:

[0027]

[0028] where V Y =(0, -1). In addition, the horizontal distance along the X-axis (coordinate system XAY) from the acting point P s of the clamping force F 5 to point D (that is, the moment arm of the clamping force F s acting on the free end of the third segment) △x 5 can be expressed by the following formula:

[0029]

[0030] where L 1 is the length of the distal phalanx, H 1 is the height of the fingertip part of the distal phalanx, H 2 is the height of the silicone fingertip part, and the angle θ 5 is approximately obtained from L 1 , H 1 and H 2 according to the vertical triangle relationship.

[0031] ② Force and moment parameters at the free end of the first section

[0032] Because the axial force of the third section C F D,x , transverse force C F D,y and moment C M D are gradually transmitted to the first section through the second section. For the third section, the static equilibrium equations are as follows:

[0033]

[0034] where C F C,x , C F C,y and C M C respectively represent the axial force, transverse force, and moment of the second section on point C of the third section.

[0035] Similarly, the static equilibrium equations of the second section are as follows:

[0036]

[0037] where - C F C,x , - C F C,y and - C M C respectively represent the axial force, transverse force, and moment of the third section on point C of the second section. According to Newton's third law, their magnitudes are equal to C F C,x , C F C,y and C M C respectively, and the directions are opposite. The direction definitions of all similar mechanical parameters in the full text follow this rule., L 2 is the length of the proximal phalanx, and the concentrated force F n = F t cosθ 2 + F t cosθ 3 , - A F B,x , - A F B,y and - A M B respectively represent the axial force, transverse force, and moment of the first section on point B of the second section. Through the above force transmission, the axial force A F B,x , transverse forceA F B,y and moment A M B .

[0038] 3. Normalization and solution

[0039] Normalize the thickness of each free deformation segment, and the forces and moments at the free ends, including the normalized length (normalized by L / N), force (normalized by N 2 EI / L2), and moment (normalized by NEI / L), to eliminate the dimensional differences and simplify the calculations:

[0040]

[0041] where E, I, and T represent the elastic modulus, cross-sectional moment of inertia, and thickness of the free deformation segment, respectively, 0 F N,x , 0 F N,y and 0 M N represent the axial force, transverse force, and moment acting on the free end of the deformation segment, respectively, 0 X N , 0 Y N and 0 θ N represent the horizontal displacement, vertical displacement, and rotation angle generated at the free end of the deformation segment, respectively.

[0042] When the manipulator performs the clamping action, the two fingers generate cooperative deformation in the width direction. The compressive deformation amount of each finger along the clamping direction is half of the initial total width W 2 of the manipulator, that is, the overall geometric constraint relationship determined by the structural characteristics of the manipulator:

[0043] A Y B +L 2 sin A θ B + C X D sin A θ B + C Y D cos A θ B +Δy 5 -s c =W 2 / 2

[0044] where the variable s c represents the compressive deformation amount of the fingertip silicone rubber. In addition, the acting point P of the clamping force F s ​5 The vertical distance Δy from point D along the Y-axis (coordinate system XAY) 5 can be expressed as follows:

[0045]

[0046] s c can be expressed as:

[0047]

[0048] where A s represents the contact area when the fingertips of two fingers touch, and the elastic modulus E S The relationship between the shear modulus G is E s = 2G(1 + ν), where ν is the Poisson's ratio, and the shear modulus G = 2C 10 where C 10 is the material constant of the Neo-Hookean model, which is measured by the tensile experiment of the silicone material.

[0049] When both the third segment and the first segment are discretized into N elements, there are a total of 12N + 14 parameters, including 12N + 12 parameters of the chain beam constraint model and F t and F s parameters. In addition, 12N + 12 equations are obtained, including 12N + 6 equations of the chain beam constraint model and the force and moment equations (a total of 6) at the free ends of the first segment and the third segment, plus the geometric constraint equations when the finger deforms. Then, when F t is known, F s can be solved by simultaneously solving the above equations (the number of unknowns is equal to the number of equations) and the displacement parameters of all elements. Conversely, when F s is known, F t can also be solved, and the displacement parameters of all elements can be obtained. Then, based on the displacement parameters of each element in the first segment and the third segment, the deformation of the integral flexible beam can be determined.

[0050] When the deformation state of the finger is determined, the displacement of the driving rope is calculated by the following formula ΔL t :

[0051] ΔL t = 2L - (||P 4 - P 3 || 2 + ||P 2 - P 1 || 2 )

[0052] The above theory can be verified by finite element analysis and experimental tests.

[0053] The beneficial effects of the present invention are mainly reflected in the following two aspects:

[0054] (1) The innovative soft manipulator adopts an integral flexible beam and a cable-driven mechanism, and is integrated with silica gel at the fingertips, which can effectively avoid the oxidation and blackening of tea bud tissues caused by traditional blade picking, and its picking effect is consistent with that of manual picking. (2) The provided precise modeling method for the clamping force establishes the relationship between the cable displacement, cable tension and the clamping force of the soft manipulator, providing a theoretical basis and technical support for the precise regulation of the clamping force of the manipulator. Description of the Drawings

[0055] Figure 1 It is a schematic three-dimensional structure diagram of an embodiment of the present invention (the frame 6 is detachably connected to the motor mounting plate 5 through bolts).

[0056] Figure 2 It is a schematic front view structure diagram of an embodiment of the present invention.

[0057] Figure 3 It is a schematic side view structure diagram of an embodiment of the present invention.

[0058] Figure 4 It is a schematic front view structure diagram of the soft manipulator of an embodiment of the present invention.

[0059] Figure 5 It is a schematic three-dimensional structure diagram of the soft manipulator of an embodiment of the present invention.

[0060] Figure 6 It is a schematic three-dimensional structure diagram of the motor mounting plate of an embodiment of the present invention.

[0061] Figure 7 It is a schematic three-dimensional structure diagram of the connecting plate of an embodiment of the present invention.

[0062] Figure 8 It is a schematic three-dimensional structure diagram of the distal phalanx of the soft manipulator of an embodiment of the present invention.

[0063] Figure 9 It is a schematic three-dimensional structure diagram of the proximal phalanx of the soft manipulator of an embodiment of the present invention.

[0064] Figure 10 It is a schematic front view structure diagram of the clamping state of an embodiment of the present invention (to clearly show the core structure, the frame is omitted, and the same structure omission method in the subsequent drawings refers to the description of this figure).

[0065] Figure 11 It is a schematic front view structure diagram of the manipulator in the clamping state of an embodiment of the present invention.

[0066] Figure 12 It is a schematic front view structure diagram of the state of rotating and lifting to pick tea buds of an embodiment of the present invention.

[0067] Figure 13 It is a schematic side view structure diagram of the collection state of the embodiment of the present invention (the manipulator clamps the picked tea buds and rotates them above the collection box, the manipulator releases, and the tea buds fall into the collection box due to gravity).

[0068] Figure 14 It is a schematic diagram of the chain beam constraint model adopted by the embodiment of the present invention.

[0069] Figure 15 It is a schematic diagram of the force analysis of the soft manipulator in the embodiment of the present invention.

[0070] Figure 16 It is a schematic diagram of the correlation of the modeling dimensions of the clamping force of the soft manipulator in the embodiment of the present invention.

[0071] Figure 17 It is a schematic diagram of the force transmission and decomposition of the soft manipulator in the embodiment of the present invention.

[0072] Figure 18 It is a comparison diagram of the results (the theory, finite element analysis and experimental tests described in the present invention) of the relationship between the deformation of the integral flexible beam, the rope tension, the rope displacement and the clamping force when the soft manipulator is in the clamping state in the embodiment of the present invention.

[0073] Reference numerals in the figure: soft manipulator 1, integral flexible beam 1-1, proximal phalanx 1-2, distal phalanx 1-3, drive rope 1-4, silica gel 1-5, base 1-6, rope connection block 1-7, servo electric cylinder 1-8, electric cylinder fixing plate 1-9, tea bud 1-10, connecting plate 2, joint motor 3, collection box 4, motor mounting plate 5, frame 6. Specific embodiments

[0074] The following is further described in conjunction with the embodiments shown in the accompanying drawings.

[0075] As Figure 1 、 Figure 2 and Figure 3 shown, the famous and high-quality tea picking device based on a soft manipulator includes a soft manipulator 1, a connecting plate 2, a joint motor 3, a collection box 4, a motor mounting plate 5, a frame 6 (used to connect the motor mounting plate to the robotic arm; preferably aluminum profile) and corresponding bolts.

[0076] The soft manipulator 1 (as Figure 4 and 5 shown) includes a base 1-6 and two fingers that are identical in structure and symmetrically fixed vertically on the base; each finger consists of an integral flexible beam 1-1, a proximal phalanx 1-2 (as Figure 9 shown), a distal phalanx 1-3 (as Figure 8It consists of two fingers (as shown), a driving rope 1-4, and silica gel 1-5; the two driving ropes 1-4 are located on the inner sides of the two fingers facing each other to drive the two fingers one by one; the two integral flexible beams are arranged vertically and the rear ends are fixed on the base, the servo cylinder is installed on the base and located between the two integral flexible beams, and its push rod passes through the opening of the base and extends upward (see Figure 4 ); the proximal phalanx 1-2 is connected to the middle position of each integral flexible beam 1-1 by bolts, and the distal phalanx 1-3 is connected to the front end of each integral flexible beam 1-1 by bolts (i.e., the lower end in Figure 4 ); the silica gel 1-5 is fixed on the distal phalanx 1-3 by glue, and the two silicas are arranged facing each other, which is used to directly contact the tea leaves when picking tea leaves and can avoid damaging the tea leaves; the rope connection block 1-7 is connected to the top end of the push rod of the servo cylinder by bolts; one end of the driving rope 1-4 is knotted on the distal phalanx 1-3 (denoted as point S 1 ), and the other end is knotted on the rope connection block 1-7 (denoted as point S 2 ); through-hole guiding holes for the driving rope 1-4 to pass through are respectively opened at the corresponding positions of the proximal phalanx 1-2 and the base 1-6 (denoted as path R 3 and R 4 ) respectively; the diameter of the hole is determined according to the diameter of the driving rope 1-4 to ensure that the gap between the driving rope 1-4 and the inner wall of the hole is extremely small, restricting the lateral offset of the driving rope 1-4 in the hole; in the theoretical model, the hole is simplified to a geometric point (dimensionless), and the contact between the driving rope 1-4 and the hole is regarded as a point constraint. If the actual hole size is too large, there may be motion errors due to the gap in finite element analysis and experiments, thus reducing the consistency with the theoretical model; the point S 1 , point S 2 , R 3 and the hole path R 4 form a straight line when connected in the initial state, ensuring that the driving rope 1-4 remains vertical and unbent when not loaded, and at the same time ensuring that the driving rope 1-4 has no pre-tension in the initial state. When the servo cylinder 1-8 is started, the rope connection block 1-7 fixed on the push rod of the servo cylinder drives the driving rope 1-4 to move upward, and the two fingers bend towards each other (as shown in Figure 11 ); when the displacement of the driving rope 1-4 reaches a certain threshold, the fingertips of the two fingers will touch, thus generating a clamping force; at the same time, since the driving rope 1-4 remains vertical in the initial state, the movement stroke of the servo cylinder 1-8 can be considered as the displacement of the driving rope 1-4.

[0077] The integral flexible beam is integrally formed by an elastic metal thin plate, and the thin plate is made of a high-elastic metal material, and the material resilience is used to maintain the controllability of the deformation during flexible bending (preferably spring steel).

[0078] The motor mounting plate 5 (as shown in Figure 6shown) is fixed on the frame 6, and the fixing surface is inclined at a certain angle (preferably 10 - 30 degrees) with respect to the motor mounting surface, so that the rotation axis of the joint motor 3 forms a corresponding angle with the plane of the frame; the connecting plate 2 (as Figure 7 shown) is bent into two planes, which are respectively used to connect the rotating shaft of the joint motor and the side surface of the base, so that both the connecting plate 2 and the motor mounting plate 5 are in an inclined "L" shape, and the angles of the two cooperate with each other so that the soft manipulator 1 is vertically downward in the initial state and in an inclined state in the collection state (at this time, driven by the joint motor, the soft manipulator rotates 180 degrees), so as to facilitate the tea buds 1 - 10 to fall into the collection box 4 under the action of gravity, as Figure 13 shown.

[0079] As Figure 15 , Figure 16 , Figure 17 and Figure 18 shown, the clamping force modeling method based on the chain beam constraint model ( Figure 14 ) can obtain the relationship between the tensions of the driving ropes 1 - 4, the displacements of the driving ropes 1 - 4 and the clamping force of the soft manipulator 1.

[0080] As Figure 14 of the chain beam constraint model, its modeling process is as follows.

[0081] (1) Discretization of the beam and definition of nodes

[0082] The flexible beam with a constant cross-section (the width and thickness are equal everywhere) is discretized into N equal-length elements along its length direction. Each element can be calculated by the beam constraint equation (Formula 6), and then the chain algorithm is used to solve the large non-linear deformation of the beam. The parameters L, T, W, E, and I respectively represent the length, thickness, out-of-plane width, Young's modulus, and area moment of inertia of the beam. The flexible beam is divided into N elements with an element length of L / N, and there are a total of N + 1 nodes (numbered 0 to N), as Figure 14 (a). Among them:

[0083] ① According to the Euler-Bernoulli beam theory, the beam is simplified to the neutral line along its length direction in mechanical analysis, and a coordinate system is established based on this line to describe the deformation behavior. Nominally, the thickness is ignored, but its physical influence is retained through the cross-sectional properties (including thickness, width, and moment of inertia) to simplify the analysis.

[0084] ② A local coordinate system is defined at each node, as Figure 14 (b). For the i-th element (where 1 ≤ i ≤ N), its local coordinate system x i-1 o i-1 y i-1 is established at node i - 1, and its x-axis is the tangent direction of this point, which rotates as the beam deforms;

[0085] ③ Node 0 is a fixed end, and the local coordinate system x of the first element is established at its location. 0 o 0 y 0 , and this coordinate system coincides exactly with the global coordinate system XOY - not only the origin coincides with the global coordinate origin, but also the coordinate axis directions are the same as those of the X and Y axes of the global coordinate system respectively. To maintain the unity of the symbol system, the global coordinate system in the present invention will follow the mathematical representation form of the local coordinate system x 0 o 0 y 0 .

[0086] ④ Node N is a free end and bears external loads. The parameters 0 F N,x , 0 F N,y and 0 M N respectively represent the axial force, transverse force, and moment applied to the flexible beam. The parameters 0 X N , 0 Y N and 0 θ N represent the horizontal coordinate, vertical coordinate, and rotation angle of the free end of the flexible beam after deformation under the action of 0 F N,x , 0 F N,y and 0 M N . Among them, the upper left superscript 0 of the parameter represents the local coordinate system x 0 o 0 y 0 , and the lower right subscript N represents the node number. The x or y after the comma represents the direction. For example, 0 F N,x represents the axial force in the x direction of node N under the local coordinate system x 0 o 0 y 0 , and 0 θ N represents the rotation angle of node N (i.e., the angle between the tangent direction of node N and the positive x-axis direction of the local coordinate system x 0 o 0 y 0 ) under the local coordinate system x 0 o 0 y 0 .

[0087] (2) Parameter normalization

[0088] When solving the chained beam constraint model, all parameters need to be normalized (made dimensionless), and then the normalized parameters are used for chained solution. All displacement and length parameters are normalized according to L / N, and the force parameters are normalized according to N 2 EI / L 2 Normalize, and the moment parameter is normalized according to NEI / L. For a flexible beam, its parameter normalization is as follows:

[0089]

[0090] Among them, the parameter 0 f N,x 、 0 f N,y and 0 m N respectively represent the normalized axial force, transverse force and moment. The parameters 0 x N 、 0 y N and 0 θ N respectively represent the normalized horizontal coordinate, vertical coordinate and rotation angle. The parameter t represents the normalized beam thickness (that is to say, the normalized parameters are represented by the corresponding lowercase letters. For example 0 f N,x represents 0 F N,x 's normalized value). For the i-th element, the parameters i-1 f i,x 、 i-1 f i,y 、 i-1 m i respectively represent the normalized axial force, transverse force and moment. The parameters i-1 x i 、 i-1 y i and α i respectively represent the normalized horizontal coordinate, vertical coordinate and rotation angle of the free end (because the solution of the chained beam constraint model only involves the normalized parameters, so the true axial force, transverse force and moment received by the free end of each element will not be elaborated here), as Figure 14 (b). Similarly, the superscript i - 1 of the parameter represents the local coordinate system x i-1 o i-1 y i-1 , the subscript i represents the node number, and x or y after the comma represents the direction. The same applies hereinafter.

[0091] (3) Force and moment transfer of the element

[0092] According to Figure 14(b), the local coordinate system of the (i + 1)-th element (where 1 ≤ i ≤ N - 1) undergoes a rigid rotation of α angle with respect to the local coordinate system of the i-th element: i Angle of rigid rotation:

[0093]

[0094] Here i f i,x 、 i f i,y 、 i m i respectively represent the transverse force, axial force, and bending moment of the i-th element on the (i + 1)-th element. The load balance equation of the (i + 1)-th element can be expressed as:

[0095]

[0096] From equations (2) and (3), the relationship between the loads at the free ends of the (i + 1)-th element and the i-th element can be expressed as follows (3(N - 1) equations):

[0097]

[0098] Since the local coordinate system x 0 o 0 y 0 of the first element coincides with the global coordinate system XOY, by analyzing the forces on the first element and the flexible beam, it can be known that the axial force 0 f 1,x and transverse force 0 f 1,y received at the free end of the first element are respectively equal to the axial force 0 f N,x and transverse force 0 f N,y received by the flexible beam. Additionally, according to the coincidence of the free ends of the N-th element and the flexible beam, the following can be obtained (3 equations):

[0099]

[0100] For the i-th element (where 1 ≤ i ≤ N), the beam constraint model equations are as follows (3N equations):

[0101]

[0102] (4) Coordinate system transformation and geometric constraints

[0103] From the local coordinate system x N o N y N to the local coordinate system x 0 o 0 y0 The homogeneous transformation matrix from the free end to the fixed end of the flexible beam can be expressed as follows:

[0104]

[0105] The local coordinate system x of the i-th unit i-1 o i-1 y i-1 The rotation angle of the local coordinate system x 0 o 0 y 0 relative to the first unit 0 θ i-1 is as follows:

[0106]

[0107] The geometric constraint equations of the flexible beam, that is, the overall normalized displacement is obtained by vector superposition of the local displacements of each unit after chain coordinate transformation, and the rotation angle is the algebraic sum of the rotation angles of each unit (3 equations):

[0108]

[0109] (5) Equation system construction and solution

[0110] According to the above analysis, there are a total of 3N equilibrium equations (Equations (4) and (5)), 3N beam constraint equations (Equation (6)), and 3 geometric equations (Equation (9)), for a total of 6N + 3 equations. For a flexible beam with its length divided into N equal-length units, each unit has 6 parameters: i-1 f i,x , i-1 f i,y , i-1 m i , i-1 x i , i-1 y i and α i , and in addition, there are 6 global parameters: 0 f N,x , 0 f N,y , 0 m N , 0 x N , 0 y N and 0 θ N , so there are a total of 6N + 6 parameters. Therefore, given the three load parameters applied to the free end of the flexible beam (i.e., 0 F N,x , 0 F N,y and0 M N ), through the piecewise recursive calculation of the chained beam constraint model, the three displacement parameters at the free end can be solved ( 0 X N 、 0 Y N and 0 θ N ) and the displacement parameters of each unit, and finally the complete deformation curve of the flexible beam can be obtained. Conversely, if the three displacement parameters at the free end are given, the corresponding load parameters can also be determined, and the deformation curve of the beam can also be obtained.

[0111] The process of the precise modeling method of the clamping force based on the chained beam constraint model is as follows.

[0112] (1) Segmentation of the integral flexible beam 1-1

[0113] Before establishing the theoretical model, the following assumptions need to be made: ① The holes on the proximal phalanx 1-2 and the base 1-6 are regarded as line segments without dimensions; ② The proximal phalanx 1-2 and the distal phalanx 1-3 are closely attached to the integral flexible beam 1-1, and the normal force exerted by the drive rope 1-4 on the proximal phalanx 1-2 is regarded as a concentrated force; ③ The influence of friction and gravity on the bending behavior of the flexible beam is ignored; ④ Since the volume of the tea stalk is small, its influence on the model can be ignored; ⑤ The drive rope 1-4 is simplified to a geometric centerline without dimensions in the analysis, and only its axial tensile stiffness is considered in the theoretical model.

[0114] As Figure 15 shown, when the manipulator is in the clamping state, one finger is subjected to the rope tension F t (the tension generated by the drive rope 1-4), the clamping force F s (the contact force generated when the mechanical fingertip closes), and the normal force F n (the vertical force exerted by the drive rope 1-4 on the proximal phalanx 1-2); the force analysis diagram of the other finger is mirror symmetric.

[0115] The coordinate points used in the modeling process are defined as follows: The termination point (adjacent to the proximal phalanx 1-2 side) of the contact area between the integral flexible beam 1-1 and the base 1-6 is defined as point A; The starting point (adjacent to the base 1-6 side) of the contact area between the integral flexible beam 1-1 and the proximal phalanx 1-2 is defined as point B; The termination point (adjacent to the distal phalanx 1-3 side) of the contact area between the integral flexible beam 1-1 and the proximal phalanx 1-2 is defined as point C; The starting point (adjacent to the proximal phalanx 1-2 side) of the contact area between the integral flexible beam 1-1 and the distal phalanx 1-3 is defined as point D; The termination point (the free end of the integral flexible beam 1-1) of the contact area between the integral flexible beam 1-1 and the distal phalanx 1-3 is defined as point G; The termination point (adjacent to the proximal phalanx 1-2 side) of the contact path between the drive rope 1-4 and the hole of the base 1-6 is defined as P1 Point; the starting point (adjacent to the base 1-6 side) of the contact path between the driving rope 1-4 and the hole of the proximal phalanx 1-2 is defined as P 2 Point; the ending point (adjacent to the distal phalanx 1-3 side) of the contact path between the driving rope 1-4 and the hole of the proximal phalanx 1-2 is defined as P 3 Point; the knotting point of the driving rope 1-4 and the distal phalanx 1-3 is defined as P 4 Point; the clamping force F s The equivalent action point of the action area (the clamping contact point of the two fingers) is defined as P 5 Point.

[0116] The included angles used in the modeling process are defined as follows: θ 2 is P 2 P 1 The included angle between the vector direction of P 2 and the vector direction of BP; θ 3 is P 3 P 4 The included angle between the vector direction of P 3 and the vector direction of CP; θ 4 is P 4 P 3 The included angle between the vector direction of P 4 and the vector direction of the D vector; θ 5 is DP 5 The included angle between the vector direction of DP and the vector direction of the DG vector. It should be noted that after the tension or displacement of the driving rope 1-4 is given, the finger realizes the bending movement through the elastic deformation of the integral flexible beam 1-1, prompting the two fingers to contact at point P 5 and form the clamping force F s , during which the above-defined included angles and coordinate points (except for point A, which is a fixed point) will be dynamically adjusted with the change of the curvature of the integral flexible beam 1-1 until the system reaches the static equilibrium state.

[0117] As Figure 16 shown, the parameters of the manipulator used in the modeling process are defined as follows (at this time, the soft manipulator 1 is in the initial state): As Figure 16 (a) Schematic diagram of the plane of the soft manipulator. The total width of the soft manipulator (i.e., the vertical distance between the integral flexible beams 1-1 of the two fingers) is defined as W 2 ; As Figure 16 (b) and (c) are the front view and side view of a single finger respectively (the left end with two holes is the fixed end of the finger for fixing on the base). The length of the distal phalanx 1-3 is defined as L 1 、the length of the proximal phalanx 1-2 is defined as L 2 、the height of the fingertip part of the distal phalanx 1-3 is defined as H 1 、the height of the fingertip part of the silicone 1-5 is defined as H2 and the vertical distance between the driving rope 1-4 and the integral flexible beam 1-1 is defined as W 1 .

[0118] According to the assumption, the integral flexible beam 1-1 from point A to point G is divided into four segments. Specifically, the first segment (from point A to point B) and the third segment (from point C to point D) can freely deform and can be regarded as separate flexible beams, and the chain beam constraint model is used for analysis. The second segment (from point B to point C) and the fourth segment (from point D to point G) are constrained and remain straight. It is assumed that both the first segment and the third segment are discretized into N equal-length units, and coordinate systems XAY and XCY are established at the leftmost end of each segment respectively. Then, according to the chain beam constraint model, a total of 12N + 12 parameters are introduced, and 12N + 6 equations can be obtained. Six unknown parameters still need to be determined, namely the 3 force and moment parameters at the free end of each of the first and third segments.

[0119] (2) Determine the force and moment parameters at the free ends of the third and first segments

[0120] During the finger deformation process, the acting point of the rope tension F t is the knot point P of the driving rope 1-4 on the distal phalanx 1-3 4 , and the direction is along the P 4 P 3 vector direction. The acting point of the clamping force F s is the equivalent acting point P of the double-finger contact area 5 , and the direction is always along the negative Y-axis direction of the coordinate system XAY. The acting point of the normal force F n is the midpoint of the hole contact section P of the proximal phalanx 1-2 2 P 3 , and the direction is perpendicular to the vector P 2 P 3 , and towards the bending deformation side of the integral flexible beam 1-1. According to the force translation theorem, the rope tension F t and the clamping force F s are first translated to the free end of the third segment and transmitted to the first segment through the second segment step by step. Therefore, first analyze the force and moment at the free end of the third segment, and then deduce the force and moment parameters of the first segment. ① Force and moment parameters at the free end of the third segment

[0121] For the third segment, which is discretized into N equal-length units, point D is equivalent to the free end (the above-mentioned node N), and point C is equivalent to the fixed end (the above-mentioned node 0). Based on formula (7), the homogeneous transformation matrix from point D to point C can be constructed using the normalized rotation angle of each unit C T D (that is, from the local coordinate system x N o N y N to x0 o 0 y 0 )。The present invention stipulates that the unit lengths of the first and third segments are both set to 1 millimeter (i.e., N = L) to ensure that the deformation of each unit can be approximated as a straight line. Then, the coordinates of points such as P 3 , P 4 and D in the XCY coordinate system can be expressed through this homogeneous transformation matrix. Taking point P 4 as an example, its coordinates in the local coordinate system x N o N y N (which is the local coordinate system established at point D) can be expressed as [W 1 , 0] T , and when extended to homogeneous coordinate form, it becomes [W 1 , 0, 1] T . By left-multiplying with the homogeneous transformation matrix C T D , that is C T D ·[W 1 , 0, 1] T , and by extracting the first two-dimensional components, the coordinates of point P 4 in the XCY coordinate system can be obtained.

[0122] The tension direction of the driving ropes 1-4, P 4 P 3 and the included angle θ 4 between the vector P 4 and P

[0123]

[0124] When the finger is not driven, θ 4 is 90°, and when the finger is driven, the angle range of θ 4 is from greater than 90° to less than 180°. Similarly, the angles θ 2 and θ 3 can also be calculated in the same way.

[0125] As shown in the force decomposition and transmission schematic diagram (Figure (a) is the force analysis diagram of the third segment, Figure (b) is the force analysis diagram of the second segment, and Figure (c) is the force analysis diagram of the first segment), the rope tension F Figure 17 and the clamping force F t and the clamping force F s can be translated and decomposed to the free end (point D) of the third segment to obtain the axial force C F D,x , the transverse force C F D,y and the moment C M D(The horizontal coordinate, vertical coordinate, and rotation angle of the free end after deformation are respectively C X D , C Y D and C θ D ). After being transmitted through the second segment, these forces are then decomposed together with the normal force F n to the free end (point B) of the first segment, obtaining the axial force A F B,x , the lateral force A F B,y and the moment A M B (The horizontal coordinate, vertical coordinate, and rotation angle of the free end after deformation are respectively A X B , A Y B and A θ B ). Translating and decomposing the rope tension F t and the clamping force F s (based on the XCY coordinate system of this segment), the force and moment parameters acting on the free end (point D) of the third segment can be obtained:

[0126]

[0127] where θ Ft represents the angle between the tension direction of the driving rope 1 - 4 and the negative y - axis of the XCY coordinate system:

[0128]

[0129] where V Y =(0, - 1). Additionally, the horizontal distance △x 5 from the action point P 5 of the clamping force F s to point D along the X - axis of the XAY coordinate system (i.e., the moment arm of the clamping force F s acting on the free end of the third segment) can be expressed by the following formula:

[0130]

[0131] where the angle θ 5 is approximately obtained from the geometric relationships L 1 , H 1 and H 2 (as shown in Figure 15 ) according to the vertical triangle relationship.

[0132] ② Force and moment parameters of the free end of the first segment

[0133] Similarly, the first section is also discretized into N equal-length units. Point B is equivalent to the free end (node N mentioned above), and point A is equivalent to the fixed end (node 0 mentioned above). Based on formula (7), the homogeneous transformation matrix from point B to point A can be obtained. A T B (that is, from the local coordinate system x N o N y N to x 0 o 0 y 0 ). Through this homogeneous transformation matrix, the coordinates of points such as P 1 , P 2 and B in the XAY coordinate system can be expressed.

[0134] As Figure 17 shown, according to the force transmission process, the static equilibrium equation of the third section is:

[0135]

[0136] where C F C,x , C F C,y and C M C respectively represent the axial force, transverse force, and moment acting on point C of the third section. C X D and C Y D represent the horizontal coordinate and vertical coordinate of the free end of the third section.

[0137] Similarly, for the second section, the static equilibrium equation can be expressed as follows:

[0138]

[0139] where - C F C,x , - C F C,y and - C M C respectively represent the axial force, transverse force, and moment of the third section acting on point C of the second section. According to assumption ②, the normal force F n = F t cosθ 2 + F t cosθ 3 , - A F B,x , - A F B,y and - A M Brespectively represent the axial force, lateral force, and moment of the I-th segment acting on point B of the II-th segment. Through the force transfer between the III-th segment and the II-th segment as described above, the force and moment parameters at the free end of the I-th segment can be obtained A F B,x 、 A F B,y and A M B 。

[0140] (3) Solving and verification

[0141] In summary, both the III-th segment and the I-th segment are discretized into N elements, with a total of 12N + 14 parameters, including 12N + 12 parameters of the chained beam constraint model and the parameters of F t and F s parameters. In addition, there are 12N + 12 equations, including 12N + 6 chained beam constraint model equations and 6 load equations (Equations (11) and (15)). The forces and moments at the free ends of the I-th segment and the III-th segment are normalized using the above formula (1). Additionally, it should be noted that when the finger is in the clamping state, there is a geometric constraint equation (when the soft finger is in the clamping state, due to the geometric constraint of the symmetric structure of the manipulator, the compression deformation of each finger along the clamping direction is half of the initial total width W 2 of the manipulator):

[0142] A Y B +L 2 sin A θ B + C X D sin A θ B + C Y D cos A θ B +Δy 5 -s c =W 2 / 2 (16)

[0143] where the variable s c represents the compression deformation of the fingertip silicone rubber. In addition, the perpendicular distance △y s from the acting point P 5 of the clamping force F 5 to point D along the Y-axis of the XAY coordinate system can be expressed as follows:

[0144]

[0145] The compression deformation s c of the silicone rubber and the clamping force F sThe relationship is as follows. According to the Neo-Hookean model, the compressive stress of the silicone under the clamping force F s is expressed as σ = F s / A s , where A s represents the contact area of the fingertip. In this embodiment, the typical value of A s is 24 mm 2 (It is found through experimental measurement and finite element analysis that when the clamping force F s is in the range of 25 - 35 N, the maximum deviation of A s does not exceed 5%). When performing modeling analysis, it is simplified to a fixed value. This simplification reduces the computational complexity while ensuring the accuracy of the model. Given that the silicone only undergoes small deformations, the stress-strain relationship can be described by the equation σ = E s *λ, where E s represents the elastic modulus of the silicone, and the parameter λ represents the strain of the silicone material, which can be expressed as λ = s c / H 2 . The relationship between the elastic modulus E S and the shear modulus G is E s = 2G(1 + ν), where ν is the Poisson's ratio, and the shear modulus G = 2C 10 , where C 10 is the material constant of the silicone, which is measured by the uniaxial tensile experiment of the silicone. Therefore, s c can be expressed as:

[0146]

[0147] Therefore, according to the 12N + 6 chain beam constraint model equations, the force and moment equations (a total of 6) at the free ends of the first and third segments, and the geometric constraint equation (16) during finger deformation, when F t is known, F s (the number of unknowns is equal to the number of equations) and the displacement parameters of all elements can be solved by simultaneously solving the above equations. Conversely, when F s is known, F t can also be solved, and the displacement parameters of all elements can be obtained. Then, according to the displacement parameters of each element in the first and third segments, the deformation of the integral flexible beam 1-1 can be determined. Additionally, it should be noted that the coordinate system XAY of the first segment is the coordinate system of the integral flexible beam 1-1. The second segment is constrained to deform into a straight line (along the tangent direction of the free end of the first segment), and the displacement parameters i- 1 x i ; i-1 y i T need to be left-multiplied by the rotation matrix [cos A θ​B , -sin A θ B ; sin A θ B , cos A θ B T , realize the mapping from the XCY coordinate system to the XAY coordinate system, and the fourth segment is constrained to deform into a straight line (along the tangent direction of the free end of the third segment).

[0148] After the deformation state of the finger is determined, the displacement of the drive ropes 1-4 is calculated by the following formula:

[0149] ΔL t = 2L - (||P 4 - P 3 || 2 + ||P 2 - P|| 21 ) (19)

[0150] Next, the verification of the clamping force accurate modeling method proposed in the embodiment of the present invention is carried out through experiments, and it is compared with the finite element method and the experimental test results. The relevant parameter values are shown in Table 1, and the tensions of the drive ropes 1-4 are set to 25N, 27.5N, 30N, 32.5N, and 35N respectively for testing. To visually represent the relationship between the tension F t of the drive ropes 1-4, the displacement ΔL t of the drive ropes 1-4, and the clamping force F s of the soft manipulator 1, the present invention adopts a sub-figure display strategy. Figure 18 (a) is a comparison diagram of the relationship between the tension F t of the drive ropes 1-4 and the displacement ΔL t of the drive ropes 1-4, including the theoretical model, finite element simulation, and experimental test results. Figure 18 (b) is a comparison diagram of the relationship between the tension F t of the drive ropes 1-4 and the clamping force F s of the soft manipulator 1. Synchronously compare the theoretical, simulation, and experimental data. From the comparison results, it can be seen that the maximum deviation of the clamping force F s is 0.36N, and the maximum deviation of the displacement ΔL t of the drive ropes 1-4 is 0.37mm. Figure 18 (c) is a comparison diagram of the deformation of the integral flexible beam 1-1 (the theoretical model, finite element method, and experimental test), and the results show high consistency (note: only the typical results when the tension of the drive ropes 1-4 is 30N are shown in the text, and the same applies to others).

[0151] Table 1 Finger parameter variables and values

[0152] ​

[0153]

[0154] The working mode of the present invention is:

[0155] (1) First, the high-quality tea picking robot identifies and locates the tea buds, and then controls the robot arm to drive the soft robot arm 1 to move to the tea bud picking point 1-10;

[0156] (2) According to the clamping force required for picking tea buds, the clamping force accurate modeling theory proposed in the embodiment of the present invention is used to calculate the displacement and tension of the driving rope 1-4. The clamping force can be accurately regulated by controlling the motion stroke of the servo electric cylinder 1-8. Figure 10 and Figure 11 Specifically, the embodiment of the present invention mainly realizes precise control of the clamping force by controlling the displacement of the drive rope 1-4. Although the tension of the drive rope 1-4 can also be used to adjust the clamping force, considering that the existing servo motor mainly realizes precise control through displacement rather than directly controlling the force output, the present invention preferably adopts a displacement control scheme to ensure the accuracy and reliability of the system.

[0157] (3) Control the joint motor 3 to realize the 180° clockwise rotation of the soft manipulator 1. During the rotation, the tea buds will be subjected to bending force and pulling force, thereby realizing picking. Figure 12 ;

[0158] (4) Joint motor 3 completes a 180° rotation, and the picked tea buds are brought to the top of the collection box. Servo cylinders 1-8 perform a stroke zeroing operation, and the tea buds fall into the collection box due to gravity. Figure 13 Then the joint motor 3 returns to the zero position (i.e. the initial reference position), and the manipulator returns to the initial state, as shown in Figure 1 , continue picking the next tea bud.

[0159] Finally, it should be noted that the above examples are only specific embodiments of the present invention, but the present invention is not limited to the above embodiments and may have many variations. All variations that can be directly derived or associated with the contents disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A software manipulator for picking high-quality tea, characterized by: The soft robot arm comprises a base (1-6), two fingers with the same structure and vertically symmetrically fixed on the base, a power source installed on the base and located between the two fingers, and two driving ropes (1-4) respectively located on opposite sides of the two fingers; each finger comprises an integral flexible beam (1-1) arranged vertically and with its rear end fixed to the base, a distal phalanx (1-3) fixed to the front end of the integral flexible beam, and a proximal phalanx (1-2) fixed to the middle part of the integral flexible beam; one end of the driving rope is connected to the distal phalanx, and the other end passes through the proximal phalanx and the base in sequence upwards before being connected to the power source.

2. The software manipulator for picking high-quality tea according to claim 1 is characterized by: The driving rope extends along the length direction of the integral flexible beam, is located on the symmetry plane in the width direction thereof, and is preset at a distance from the surface of the flexible beam to form a bending force arm structure; when the driving rope is pulled, a bending moment is applied to the flexible beam to cause it to produce a directional bending deformation, thereby causing the fingertips of the two fingers to contact and generate a clamping force.

3. The software manipulator for picking high-quality tea according to claim 2 is characterized in that: Silica gel (1-5) is fixed on the two distal phalanges, and the two silica gels are arranged opposite to each other to prevent the tea leaves from being damaged when being picked.

4. The software manipulator for picking high-quality tea according to claim 3 is characterized by: The power source is a servo electric cylinder (1-8); an opening is made on the base to facilitate the passage of the servo electric cylinder push rod.

5. The software manipulator for picking high-quality tea according to claim 4 is characterized in that: The base and the corresponding positions of the proximal phalanx are respectively provided with holes for the driving rope to pass through and guide.

6. The software manipulator for picking high-quality tea according to claim 5 is characterized by: The soft manipulator is fixed on the rotating shaft of the joint motor through a connecting plate (2) and a motor mounting plate (5) which are connected in sequence; the connecting plate and the motor mounting plate are in an inclined "L" shape, and the angles of the two are coordinated with each other so that the initial state of the soft manipulator is vertically downward, and the collection state is inclined, so that the tea buds fall into the collection box under the action of gravity.

7. The precise modeling method for the clamping force of the software manipulator for picking high-quality tea according to claim 1 is adopted, and the following steps are performed: 1) Mechanical analysis of the integral flexible beam segment of the soft manipulator The integral flexible beam of the soft manipulator is divided into two free deformation segments and two constraint segments in a straight line along its length, and each free deformation segment is analyzed using a chain beam constraint model. 2) Calculate and determine the force and moment borne by the free end of each free deformation segment; 3) The forces and moments at the free end of each free deformation segment are normalized, including the normalization of length, force, and moment, to eliminate dimensional differences and simplify calculations; 4) Solve and obtain the clamping force of the soft manipulator.

8. The precise modeling method for the clamping force of the software manipulator for picking high-quality tea according to claim 7 is characterized by: The calculation method of step 2) is carried out according to the following steps: (1) First, establish a coordinate system at the starting end of each free deformation segment, discretize the free deformation segment into N equal-length units in the length direction, and obtain N+1 nodes; (2) Establishing a local coordinate system at each node to obtain a homogeneous transformation matrix from the free end to the starting end of each free deformation segment; then using the homogeneous transformation matrix and the geometric parameters of the finger to decompose the driving rope tension and clamping force to the free end of the second free deformation segment, the axial force, lateral force and moment components of the flexible beam are obtained; (3) Finally, the load of the second free deformation segment and the concentrated force on the proximal phalanx are transferred to the free end of the first free deformation segment and converted into equivalent load components in the coordinate system of the first free deformation segment.

9. The precise modeling method for the clamping force of the software manipulator for picking high-quality tea according to claim 8 is characterized by: The homogeneous transformation matrix from the free end to the starting end of each free deformation segment in step (2) is: where α i represents the normalized rotation angle of each unit, L represents the length of each free deformation segment, and N represents the number of segments (i.e. the number of units) of each free deformation segment, to express the coordinates of each point in the XAY and XCY coordinate systems.

10. The precise modeling method for the clamping force of the software manipulator for picking high-quality tea according to claim 9 is characterized by: The solution method of step (4) is: after the rope tension is given, the normalized force and moment of each free deformation segment are substituted into the chain beam constraint model, and the clamping force and the deformation curve of the integral flexible beam can be obtained by combining the overall geometric constraint equation.

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