Peanut plant general modeling method based on discrete element method
By using the discrete element method (DEM) to model peanut plants, combined with geometric and mechanical models, the problems of large computational scale and slow speed in existing technologies are solved, achieving efficient and accurate peanut plant simulation and supporting the optimization of peanut harvesting machinery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-07
AI Technical Summary
Existing peanut plant modeling methods mostly employ particle aggregation, resulting in excessively large simulation calculation scales, slow speeds, and difficulties in parameter calibration, making it difficult to meet the needs of efficient, precise, and intelligent development of peanut harvesting machinery.
A general modeling method for peanut plants based on the discrete element method was adopted. By analyzing the plant's geometric morphology and characteristic dimensions, the type and arrangement of the constituent particles were determined, the coordinates were calculated, and the contact mechanics and adhesion mechanics parameters were measured to establish a geometric and mechanical model. The model was then input into the discrete element software and a combination modeling method using a combination of segmented conical segments of the main stem/main root and cubic function changes of the tangential angle of the first branch/fruit needle/lateral root was adopted.
It significantly reduces the computational scale, improves the simulation speed, and can accurately represent the contact-friction-separation-fracture characteristics of plants during mechanical operations, providing precise data support for the evaluation of the interaction between peanut plants and key components of harvesters and parameter optimization.
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Figure CN121809199A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of plant modeling analysis, and particularly relates to a general peanut plant modeling method based on a discrete element method. BACKGROUND
[0002] As one of important oil crops and economic crops, the overall yield and unit area output of peanuts have been continuously increasing in recent years with the optimization and adjustment of planting structure, the scale production and the improvement of management level. Peanut harvesting mainly adopts segmented harvesting. In simple terms, the first stage is peanut lifting, and the second stage is peanut picking. In the first stage of peanut lifting, since peanuts are complex plants with underground fruiting and aboveground flourishing, the stems and root systems are complexly interwoven, the branches are numerous, and the connection between the fruit needles and the pods is fragile, which all bring great challenges to the lifting operation. Especially in the interaction with the soil and the harvesting tools, damage, shedding, fruit breaking and other phenomena often occur, which seriously affect the harvesting efficiency and quality of peanuts. At present, the peanut lifting process still mainly relies on physical tests and field experiments for tool optimization. This way not only has a long cycle and high cost, but also is affected by multiple factors such as environment, soil moisture and mechanical properties, and is difficult to meet the needs of efficient, accurate and intelligent development of peanut harvesting machinery.
[0003] The discrete element method (DEM) can provide an effective numerical simulation means for the operation mechanism research of peanut segmented harvesting: it can explicitly represent and calculate the nonlinear processes such as multi-body contact, friction, separation and (adhesion caused) fracture between the plant, soil and tool, so as to reproduce the influence of different working conditions on the operation quality in a virtual environment. However, as of now, there is still a lack of published and reasonably structured peanut plant DEM modeling method. The existing public plant modeling mostly adopts the general idea of particle aggregation (multi-sphere filling), which can describe the detailed morphology, but often needs a large number of particles to maintain geometric continuity and mechanical response, resulting in too large calculation scale, slow speed and difficult parameter calibration in the simulation process. Therefore, it is urgent to research a peanut plant modeling method based on the discrete element method, which can ensure the reasonable hierarchy and connection relationship of each part of the peanut plant, and balance the modeling efficiency and simulation stability, so as to explore the stress and deformation mechanism of peanut lifting stage, and efficiently evaluate the contact-interaction between each part of the peanut plant and the key components of the agricultural tools. SUMMARY
[0004] The present application is proposed to solve the problem that the existing peanut plant modeling mostly adopts particle aggregation, which can describe the detailed morphology, but needs a large number of particles to maintain geometric continuity and mechanical response, resulting in too large calculation scale, slow speed and difficult parameter calibration in the simulation process, and further proposes a general peanut plant modeling method based on the discrete element method.
[0005] The technical scheme adopted by the present application is:
[0006] It comprises the following steps:
[0007] S1, analyze the geometric shape and characteristic size of each part of the peanut plant;
[0008] S2, based on S1, determine the type and arrangement of the spherical particles composed of the geometric model of the peanut plant;
[0009] S3, according to the arrangement mode of S2, calculate the coordinates of the spherical particles composed of each part of the peanut plant;
[0010] S4, establish the geometric model of the peanut plant according to the coordinates of the spherical particles composed of each part of the peanut plant;
[0011] S5, based on the geometric model of the peanut plant, measure and calibrate the contact mechanics parameters and adhesion mechanics parameters of each part of the peanut plant;
[0012] S6, add the contact mechanics parameters and adhesion mechanics parameters of each part of the peanut plant to the mechanics model to obtain the added mechanics model;
[0013] S7, input the geometric model of the peanut plant and the added mechanics model into the discrete element software to obtain the peanut plant model.
[0014] The beneficial effects of the present application are:
[0015] Based on a large amount of measurement and statistical analysis, the present application proposes the key characteristic size parameters required for peanut plant modeling and their mutual relationship (such as the tapering section parameters of the main stem / main root, the tangential angle parameters of the first branch / fruit needle / side root curve, etc.), thereby providing important data support for the feasibility and accuracy of peanut plant modeling. The present application adopts a combination modeling of "main stem / main root segmented tapering (fast tapering section + slow tapering section) + tangential angle change of the first branch / fruit needle / side root cubic function", which significantly reduces the number of necessary particles and contacts while maintaining geometric accuracy and mechanical continuity, making parameter calibration much simpler than before, thereby reducing the calculation scale of discrete element, shortening the simulation time, and improving the simulation speed.
[0016] The present application drives the geometric and mechanical modeling of the peanut plant through adjustable parameters (length, radius, connection end expansion angle, non-connection end tangential angle), which can quickly adapt to different varieties, cultivation conditions and mature / drying stages, and can accurately represent the contact-friction-separation / breaking characteristics of the peanut plant during mechanical operations such as picking up and picking up, thereby providing more accurate data support for the interaction evaluation and parameter optimization of the peanut plant and key components of the harvesting machine. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 Photo of a peanut plant;
[0018] Figure 2 This is a schematic diagram of a peanut plant model;
[0019] Figure 3 A schematic diagram of the various parts of a peanut plant.
[0020] Figure 4 A schematic diagram of the main stem, taproot, and first branching cone segment;
[0021] Figure 5 A schematic diagram defining the angles of the first branching, fruit pegs, and lateral roots;
[0022] Figure 6 This is the main view of the first branch distribution at each level;
[0023] Figure 7 This is a top view of the first branching distribution at each level;
[0024] Figure 8 Front view of the distribution of lateral roots in odd and even order;
[0025] Figure 9 A top view of the distribution of lateral roots in odd and even order;
[0026] Figure 10 The figures shown are tensile and shear test diagrams of different parts of the peanut plant in the example, where (a) is the stem tensile test, (b) is the peg tensile test, (c) is the root tensile test, (d) is the stem shear test, (e) is the peg shear test, and (f) is the root shear test.
[0027] Figure 11 The following are tensile test diagrams of the stem and fruit needle nodes in the embodiment, where (a) is before node breakage and (b) is after node breakage.
[0028] Figure 12 This is a simulation diagram of the peanut harvesting process using a chain rake in the embodiment.
[0029] Figure 13 This is a simulation diagram of the peanut harvesting process using a chain rake, illustrating the effect of spreading the peanuts. Detailed Implementation
[0030] Specific implementation method one: Combining Figures 1-9 This embodiment describes a general modeling method for peanut plants based on the discrete element method, which includes the following steps:
[0031] S1, such as Figure 1 As shown, the peanut variety Jinonghua 7, which is representative of Northeast China, was selected as the research object to analyze the geometric morphology and characteristic size parameters of various parts of the peanut plant.
[0032] The geometry includes:
[0033] (1) The peanut plant structure and the tapering characteristics of the main stem and the primary root:
[0034] The peanut plant is composed of a main stem, a primary root, a multi-branch first branch, a multi-root gynophore, and a multi-root lateral root. The main stem and the primary root are connected end to end along the same axis, and the junction of the main stem and the primary root is defined as the axial starting point. Along the length direction of the main stem and the primary root at the axial starting point, it is found that the cross-sectional radius of the two is monotonically decreasing, and presents a segmented tapering characteristic of "rapid decay-slow decay". The rapid tapering segment is a segment of length from the transition point of the maximum radius to the starting point of the flat radius on the main stem or the primary root in the vicinity of the root-stem junction. The rapid tapering segment is followed by a slow tapering segment, and the radius of the slow tapering segment decreases slowly and remains continuous and smooth. The geometry and slope at the connection between the rapid tapering segment and the slow tapering segment are continuous. Therefore, the present application sets that the main stem is composed of one rapid tapering segment and three continuous slow tapering segments, the primary root is composed of one rapid tapering segment and two continuous slow tapering segments, and the radius of all the constituent spherical particles in each slow tapering segment is constant and takes a fixed value. The setting of the rapid tapering segment and the slow tapering segment facilitates the reconstruction of the cross-sectional variation of the main stem and the primary root with a small number of parameters, and at the same time matches the actual stress form.
[0035] (2) The spreading law of the first branch and the gynophore:
[0036] As shown in Figure 2 and Figure 3 , the first branch and the gynophore both have a larger curvature at the connection end (the connection end of the first branch and the main stem and the connection end of the first branch and the gynophore), the radius gradually decreases along the length direction from the connection end, and the non-connection end (the other end opposite to the connection end) tends to be linear, which is a typical form of "bent connection end and straight non-connection end". Unlike the main stem, no significant rapid tapering segment is observed in the first branch, and the first branch is continuously spliced by multiple slow tapering segments along the length direction, and the growth direction is upward and outward from the connection end. The gynophore starts at the connection end of the first branch and spreads downward and outward, and the radius difference of the gynophore is relatively small, and a constant radius is used in modeling. The position of the first branch in the global coordinate is determined after rotation around the main stem axis, and the gynophore is also determined by rotating at the same angle as the main stem.
[0037] (3) The arrangement and simplification of the lateral root:
[0038] Lateral roots are mostly buried underground, making it difficult to observe their stable posture over long periods. To ensure consistency between the lateral roots and the plant's overall morphology and stress transmission, multiple levels of lateral roots are distributed circumferentially at equal intervals in an approximately fan-shaped pattern in the lower part of the main root, with the lateral roots extending downwards and outwards as a whole. The radius of a single lateral root is relatively uniform within the same plant and can be accurately expressed using a constant diameter. The position of the lateral root in the global coordinate system is determined by rotating it around the main root axis.
[0039] like Figures 2~5 As shown, based on observations of the geometric morphology of peanut plants, the characteristic dimensions of peanut plants can be determined to include at least the length and radius of each part, as well as the spreading angle of the connection points of the first branching, pegs, and lateral roots. Tangential angle at non-connected end and quantity The radius can be further subdivided into the maximum radius. and minimum radius This determines the range of granular radii for the main stem, taproot, and first branching. The fruit stalks and lateral roots are measured using the average radius. Determine the radius of its constituent spherical particles. Spread angle at the connecting end. The angle between the tangent at the first branching point, fruit needle, or lateral root and the horizontal direction; the tangential angle at the non-connecting point. The angle between the tangent at the non-connecting end of the first branch, fruit needle, or lateral root and the vertical direction.
[0040] S2. Based on S1, determine the types of spherical particles that make up the geometric model of the peanut plant, including spherical particles composed of each conical segment of the stem, spherical particles composed of the pegs, and spherical particles composed of each conical segment of the root. The stem includes the main stem and the first branch, and the root includes the main root and the lateral root.
[0041] Based on the aforementioned type, the arrangement of the geometric model of the peanut plant consists of the arrangement of the main stem as a sphere, the arrangement of the first branch as a sphere, the arrangement of the pegs as a sphere, the arrangement of the main root as a sphere, and the arrangement of the lateral roots as a sphere.
[0042] Based on the analysis of the main stem and main root in S1, the main stem and main root are arranged into spherical particles using piecewise linear function relationships (including rapid conic sections and slow conic sections).
[0043] Based on the analysis of the first branching, fruit spurs, and lateral roots in S1, the angle of the first branching, fruit spurs, and lateral roots is set to the tangential angle of the line connecting the centers of the constituent spheres. A gradual control method based on cubic function variation is used to arrange the constituent spherical particles.
[0044] S3. Based on the arrangement in S2, the coordinates of the constituent particles in each part of the peanut plant are calculated. The specific process is as follows:
[0045] As Figure 4 shown, since the aforementioned setting stem is composed of 1 fast tapering section and 3 slow tapering sections, the present application sets the length ratio of each tapering section to the length of the stem as , , , , the ratio of the minimum radius to the maximum radius in the fast tapering section, i.e. the radius of the constituent spherical particles in the fast tapering section decreases linearly from the maximum radius of the stem connection end to the minimum radius of the fast tapering section . Thus, the number of constituent spherical particles in the fast tapering section of the stem is expressed as:
[0046] (1)
[0047] wherein, is the length of the fast tapering section of the stem. If the number of constituent spherical particles is not an integer, the number of constituent spherical particles needs to be rounded to the nearest integer in order to more specifically approximate the actual length of the stem.
[0048] The radius of the constituent spherical particles in the fast tapering section of the stem is expressed as:
[0049] (2)
[0050] wherein, is the radius of the th constituent spherical particle in the fast tapering section of the stem, is the radius step of the stem for the transition of the radius of adjacent constituent spherical particles in the fast tapering section, so as to strictly satisfy and wherein, is the radius of the 1st constituent spherical particle in the fast tapering section of the stem, is the radius of the th constituent spherical particle in the fast tapering section of the stem.
[0051] The axial coordinate of the constituent spherical particles in the fast tapering section of the stem is expressed as:
[0052] (3) wherein,
[0053] is the axial coordinate of the th constituent spherical particle in the fast tapering section of the stem.
[0054] The radius and number of the constituent spherical particles in the 2nd, 3rd and 4th slow tapering sections of the main stem 3 are respectively represented as:
[0055] (4)
[0056] (5)
[0057] wherein, is the radius of the constituent spherical particle in the 1st slow tapering section of the main stem, is the number of the constituent spherical particles in the 2nd slow tapering section of the main stem, is the number of the constituent spherical particles in the 3rd slow tapering section of the main stem, is the number of the constituent spherical particles in the 4th slow tapering section of the main stem, is the minimum radius of the main stem, is the length of the 2nd slow tapering section, is the length of the 3rd slow tapering section, is the length of the 4th slow tapering section.
[0058] The axial coordinates of the constituent spherical particles in the 2nd, 3rd and 4th slow tapering sections of the main stem are represented as:
[0059] (6)
[0060] wherein, is the axial coordinate of the 1st constituent spherical particle in the 1st slow tapering section of the main stem, is the axial coordinate of the 1st constituent spherical particle in the 2nd slow tapering section of the main stem, is the axial coordinate of the 1st constituent spherical particle in the 3rd slow tapering section of the main stem, is the axial coordinate of the 1st constituent spherical particle in the 4th slow tapering section of the main stem, , , is the axial coordinate of the 1st constituent spherical particle tangent to the 1st constituent spherical particle in the slow tapering section of the main stem, is the radius of the 1st constituent spherical particle tangent to the 1st constituent spherical particle in the slow tapering section of the main stem.
[0061] The axial coordinate of the 1st constituent spherical particle in the 1st tapering section of the main stem is represented as:
[0062] (7)
[0063] Since the aforementioned taproot is provided with 1 fast tapering section and 2 slow tapering sections, the taproot is parameterized with the same multi-tapering section parameters as the main stem. Assuming that the total length of the taproot is , the ratios of the lengths of the tapering sections of the taproot to the length of the taproot are respectively , , the maximum radius of the taproot connecting end is the minimum radius of the taproot non-connecting end is As shown in Figure 3 and Figure 4 , the calculation direction of the taproot is the reverse direction of the axis, opposite to the calculation direction of the main stem, and the corresponding number, radius and axis coordinate are calculated according to the reverse direction. Similarly to the main stem, the radius, number and axis coordinate of the taproot composed of each conical segment are respectively:
[0064] The number of the composed spherical particles in the fast conical segment of the taproot is:
[0065] (8)
[0066] wherein, is the length of the fast conical segment of the taproot, is the ratio of the minimum radius to the maximum radius in the fast conical segment of the taproot.
[0067] The radius of the composed spherical particles in the fast conical segment of the taproot is expressed as:
[0068] (9)
[0069] wherein, is the radius of the th composed spherical particle in the fast conical segment of the taproot, is the radius step of the taproot.
[0070] The axis coordinate of the composed spherical particles in the fast conical segment of the taproot is:
[0071] (10)
[0072] wherein, is the th composed spherical particle in the fast conical segment of the taproot.
[0073] The radius and number of the composed spherical particles in the two slow conical segments 2, 3 of the taproot are respectively:
[0074] (11)
[0075] (12)
[0076] wherein, is the the radius of the constituent sphere particle in the first slow tapering section, the minimum radius of the main root, the minimum radius of the main root, the number of constituent sphere particles in the first slow tapering section, the length of the first slow tapering section 2, the length of the second slow tapering section 3.
[0077] the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, is expressed as:
[0078] (13)
[0079] wherein, the minimum radius of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the radius of the constituent sphere particle in the first slow tapering section 2 of the main root. the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the radius of the constituent sphere particle in the first slow tapering section 2 of the main root.
[0080] the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, is expressed as:
[0081] (14)
[0082] wherein, the first tapering section corresponds to one fast tapering section (1) and two slow tapering sections (2) of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the axial coordinate of the constituent sphere particle in the first slow tapering section 2 of the main root, the radius of the constituent sphere particle in the first slow tapering section 2 of the main root. the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function,
[0083] the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, the tangent angle of the connecting line between the centers of the adjacent constituent sphere particles changes as a cubic function, Figure 5 As shown, the curvature of the bend is determined by the actual measured unfolding angle of the connection end. Tangential angle of non-connected ends Controlled, tangential angle The functional expression is as follows:
[0084] (15)
[0085] in, Indicates multiplication. These are the first branching, fruit pegs, or lateral roots, respectively. For the first branch Upper Within the first gentle conical transition segment The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. For the first Root and fruit needle Inner The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. For the first Roots and lateral roots Inner The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. . The angle step size factor, , , This refers to the number of constituent granules of the first branch, fruit stalk, or lateral root.
[0086] Unlike the main stem, the first branch does not have a rapid conical segment; instead, it consists of three slow conical segments of equal length. Therefore, the radius and number of the spheres formed by each slow conical segment of the first branch are expressed as follows:
[0087] (16)
[0088] (17)
[0089] in, For the first branch The radius of the spherical particles within each conical segment, at this time These correspond to the three gently conical segments of the first branching. The maximum radius of the first branch. Let be the minimum radius of the first branch. For the first The number of constituent spherical particles in each tapered segment This refers to the length of the first branching of each branch.
[0090] The constituent spherical particles within the first branch The axis coordinates are:
[0091] (18)
[0092] The constituent granules within the fruit needle or lateral root The axis coordinates are:
[0093] (19)
[0094] (20)
[0095] After determining the tangential angle In summary, the local coordinates of the first branch, fruit bud, or lateral root can be obtained, represented as:
[0096] (twenty one)
[0097] in, For the first branch Within the first gentle conical transition segment Each of the constituent spherical particles Axis coordinates For the first The first fruit needle Each of the constituent spherical particles Axis coordinates For the first The first lateral root Each of the constituent spherical particles Axis coordinates For the first branch Upper Within the first gentle conical transition segment The coordinates of the constituent particles of the sphere For the first Root and fruit needle Inner The coordinates of the constituent particles of the sphere For the first Roots and lateral roots Inner The coordinates of the constituent particles of the sphere On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first The radius of each constituent particle of the sphere For the first branch Upper Within the first gentle conical transition segment The radius of each constituent particle of the sphere For the first Root and fruit needle Inner The radius of each constituent particle of the sphere For the first Roots and lateral roots Inner The radius of each constituent particle of the sphere Indicates multiplication. On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates. If the first... If a constituent sphere is the starting point of a branch (root), then the coordinates and radius of the constituent sphere that is connected to the main stem, first branch, or main root of that branch (root) are represented.
[0098] The local coordinates are transformed to the corresponding global coordinates.
[0099] like Figure 3 As shown, the first branch is divided into different types according to its connection position with the main stem. The first branch of the first stage forms a spherical granule with the bottom of the main stem. The connection is tangential, with the starting point of the first branch at each level and the starting point of the first branch at the next level separated by a constituent granule on the main stem, and so on.
[0100] First branch Number of branches at each level Represented as:
[0101] (twenty two)
[0102] in, This represents the total number of branches in the first branching phase.
[0103] The conversion of the local coordinates of the first branch to global coordinates requires a detour. The axis rotates counterclockwise by a certain angle, such as Figure 6 and Figure 7 As shown, the rotation angle is expressed as:
[0104] (twenty three)
[0105] in, For the first branch Level 1 Branches The angle of counterclockwise rotation of the axis, , is the total number of first branches. Then the first branch is transformed by the rotation matrix about the axis anticlockwise is expressed as:
[0106] (24)
[0107] So the global coordinate of the first branch is expressed as:
[0108] (25)
[0109] As shown in Fig. 2, each first branch is connected with three fruit needles, the starting point of the first fruit needle is tangent to the fourth constituent sphere particle of the first branch, the starting point of the second fruit needle is tangent to the constituent sphere particle which is three constituent sphere particles away from the starting point of the first fruit needle, and so on, that is, the starting point of each fruit needle is Figure 3 . The global coordinate of the fruit needle is only transformed by the rotation matrix about the axis anticlockwise with the first branch, so the global coordinate of the fruit needle is expressed as:
[0110] (26)
[0111] The radius of each fruit needle is , and the number of constituent sphere particles of each fruit needle is , is the length of each fruit needle, where is the fruit needle, .
[0112] Similar to the first branch, the lateral roots are classified according to the connection position with the main root, and each level has four lateral roots. The first lateral root is tangent to the constituent sphere particle of the main root, the starting point of the second lateral root is tangent to the constituent sphere particle which is one constituent sphere particle away from the starting point of the first lateral root, and the starting point of the higher level lateral root is tangent to the constituent sphere particle which is one constituent sphere particle away from the starting point of the lower level lateral root.
[0113] During the harvesting process of peanuts, the lateral roots will be missing or damaged to different degrees, so the number of lateral roots is calculated by the length of the main root, and the total number of lateral roots is expressed as:
[0114] (27)
[0115] The higher the level of the lateral root, the more the number of constituent sphere particles, and the number of constituent sphere particles of each lateral root is expressed as:
[0116] (28)
[0117] where, is the total length of the single lateral root, , represents the radius of the spherical particle composed of the single lateral root.
[0118] The transformation of the local coordinates of the lateral root to the global coordinates also needs to rotate a certain angle counterclockwise around the axis, and the odd level lateral root rotates more than the even level lateral root by 45° counterclockwise around the axis, as shown in Figure 8 and Figure 9 , the rotation angle is represented as:
[0119] (29)
[0120] where, represents the angle of the th lateral root of the th level of the lateral root rotating counterclockwise around the axis, .
[0121] The transformation matrix of rotating counterclockwise around the axis is represented as:
[0122] (30)
[0123] Therefore, the global coordinates of the lateral root are represented as:
[0124] (31)
[0125] The local coordinates of the first branch and the fruit needle and the lateral root are converted to the global coordinates, and the rotation angle is represented as:
[0126] (32)
[0127] where, represents the angle of the th branch of the th level rotating counterclockwise around the axis, which is the same angle as the th lateral root when (fruit needle) and the th lateral root when , represents the total number of branches (roots) of the th level, represents the total number of .
[0128] In summary, the global coordinates of the first branch or fruit needle or lateral root can be expressed as:
[0129] (33)
[0130] wherein, represents a rotation transformation matrix of the local coordinates rotating counterclockwise around the axis.
[0131] S4, a geometric model of the peanut plant is established according to the coordinates of the spherical particles composed of each part of the peanut plant.
[0132] S5, based on the geometric model of the peanut plant, the contact mechanics parameters and the bonding mechanics parameters of each part of the peanut plant are measured and calibrated. The specific process is:
[0133] Based on the geometric model of the peanut plant, the contact mechanics parameters of each part of the peanut plant are measured and calibrated by means of a high-speed camera using methods such as drop rebound and inclined plane method. The contact mechanics parameters include the collision restitution coefficient , the static friction coefficient and the rolling friction coefficient . Among them, the collision restitution coefficient is used to represent the elastic recovery ability of the spherical particles or plant organs in the mutual collision process, and the static friction coefficient and the rolling friction coefficient are used to represent the frictional resistance between the plant and the soil and the surface of the machine. The collision restitution coefficient is determined by the drop rebound method, and is calculated by controlling the drop height and recording the rebound height; the static friction coefficient and the rolling friction coefficient are respectively determined by methods such as the inclined plane method, and the critical slip and rolling start state are recorded by slowly changing the inclination angle of the test sample and different contact surfaces. The above test process is combined with a high-speed camera to finely analyze the contact process, so as to obtain the contact mechanics parameters suitable for discrete element simulation.
[0134] As shown in Figure 10 and Figure 11 , the tensile (normal) and shear tests (tangential) of the test sample are carried out using a universal material testing machine, and the load-displacement curve is recorded synchronously to obtain the bonding mechanics parameters of each part of the peanut plant. The bonding mechanics parameters include bonding stiffness coefficient and bonding strength, and the bonding stiffness coefficient includes unit area normal stiffness and unit area tangential stiffness , which are obtained according to the slope of the linear elastic section. The bonding strength includes normal strength and tangential strength , which are determined by the limit stress at the time of fracture. The bonding strength parameters are used to represent the critical load of the combined part under the action of tension or shear to cause fracture and fall off.
[0135] The bonding mechanical parameters calibrated by the above experiment can be directly used to determine the stiffness and strength threshold of each bonding key in the discrete element model, so as to truly reflect the breaking and falling characteristics of the peanut plant during the picking process.
[0136] S6, the contact mechanical parameters and the bonding mechanical parameters of each part of the peanut plant are added to the mechanical model, the mechanical model comprises a contact model and a bonding model, the contact model is a Hertz-Mindlin contact model, and the bonding model is a Bonding model. The specific process is as follows:
[0137] The contact mechanical parameters (collision restitution coefficient , static friction coefficient and rolling friction coefficient ) are added to the contact model, and the bonding mechanical parameters (unit area normal stiffness , unit area shear stiffness , normal strength and shear strength ) are added to the bonding model.
[0138] S7, the geometric model and the mechanical model of the peanut plant are input into the discrete element software, so as to obtain the peanut plant model based on the discrete element method. The discrete element software is EDEM software.
[0139] Embodiment
[0140] The method of the application is described by means of specific examples, and the peanut plant model of Jinnonghua No. 7 is created by using the general modeling method of the peanut plant provided by the application, and the specific steps are as follows:
[0141] I. 20 Jinnonghua No. 7 peanuts are randomly selected, and the characteristic size of the peanut plant is measured using a digital vernier caliper with an accuracy of 0.01 , and the average value parameters are shown in Tables 1 and 2:
[0142] Table 1
[0143]
[0144] Table 2
[0145]
[0146] II. According to the measured characteristic size parameters of the peanut plant, the plant model parameters are shown in Table 3:
[0147] Table 3
[0148]
[0149] III. The coordinates of the spherical particles of each part of the peanut plant are solved, as shown in Table 4:
[0150] Table 4
[0151]
[0152] Four, the contact mechanics parameters of each part of peanut plant are measured and obtained as shown in Table 5, including collision recovery coefficient, static friction coefficient and rolling friction coefficient.
[0153] Table 5
[0154]
[0155] Five, the adhesion mechanics parameters of each part of peanut plant are measured and obtained as shown in Table 6, including unit area normal stiffness, unit area tangential stiffness, normal strength and tangential strength.
[0156] Table 6
[0157]
[0158] Six, the contact mechanics parameters and the adhesion mechanics parameters of each part of peanut plant are input into the discrete element software, and the peanut plant model of Jinnonghua No. 7 is obtained.
[0159] Seven, as shown in Figure 12 and 13 , the peanut plant model of Jinnonghua No. 7 generated by the above steps is imported into the discrete element software to construct a field peanut harvesting simulation test:
[0160] Compared with the real peanut plant, the peanut plant model is simplified in structure, and the leaf part is removed; this treatment significantly reduces the total number of component ball particles in the peanut plant model, effectively reduces the calculation scale while retaining the core mechanical skeleton characteristics of the plant, thereby greatly improving the efficiency and speed of simulation solution; at the same time, the “peanut pod” model appearing in the simulation scene of the embodiment is only used as a carrier to verify the load characteristics of the plant, and it is constructed by using the general discrete element multi-sphere filling technology (Multi-sphere).
[0161] In the simulation verification process, the working speed of the receiver is set to 0.9 m / s, the process of the digging shovel cutting into the soil and lifting and conveying the whole plant is simulated. Thanks to the accurate branch angle in the peanut plant model and the node connection parameter setting based on Bonding V2 (Bonding second-generation model), the plant shows the flexible bending, adaptive deformation and elastic rebound behavior conforming to the biophysical characteristics when it is subjected to the violent stirring and conveying impact of the chain harrow teeth, effectively overcoming the defects of the traditional simplified model that regards the plant as a rigid body, resulting in rigid motion posture and penetration interference. The simulation results show that the peanut plant simulated by the peanut plant model can smoothly turn over and fall after leaving the implement, forming a continuous, neat and consistent direction of the spreader behind the machine, and the final laying rate (qualified laying rate) is as high as 98.8%, and the extremely low plant scattering degree is highly consistent with the actual field operation effect. The above test verifies the feasibility of the peanut plant modeling method, which can be used for the simulation analysis of the peanut lifting process in the peanut segmented harvesting.
[0162] The present application can also have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and modifications should all belong to the protection scope of the claims attached to the present application.
Claims
1. A general modeling method for peanut plants based on the discrete element method, characterized in that: It includes the following steps: S1. Analyze the geometric morphology and characteristic dimensions of various parts of the peanut plant; S2. Based on S1, determine the type and arrangement of the spherical particles that make up the geometric model of the peanut plant; S3. Based on the arrangement in S2, calculate the coordinates of the spherical particles that make up each part of the peanut plant; S4. Establish a geometric model of the peanut plant based on the coordinates of the spherical particles that make up each part of the peanut plant. S5. Based on the geometric model of the peanut plant, measure and calibrate the contact mechanical parameters and adhesive mechanical parameters of various parts of the peanut plant. S6. Add the contact mechanical parameters and adhesion mechanical parameters of each part of the peanut plant to the mechanical model to obtain the added mechanical model; S7. Input the geometric model of the peanut plant and the added mechanical model into the discrete element method software to obtain the peanut plant model.
2. The general modeling method for peanut plants based on the discrete element method according to claim 1, characterized in that: The geometric morphology of each part of the peanut plant in S1 includes: A peanut plant consists of a main stem, a taproot, multiple first branches, multiple pegs, and multiple lateral roots; The main stem is defined as consisting of one rapid conical segment and three slow conical segments; the main root consists of one rapid conical segment and two slow conical segments; each branch's first branch consists of multiple slow conical segments; the radius of each fruit spur and each lateral root is a constant value; and the radius of each slow conical segment is a constant value.
3. The general modeling method for peanut plants based on the discrete element method according to claim 2, characterized in that: The characteristic dimensions of various parts of the peanut plant in S1 include: The length and radius of the main stem, the length and radius of the main root, the length, radius, spreading angle of the connecting end, tangential angle of the end and number of the first branch, the length, radius, spreading angle of the connecting end, tangential angle of the end and number of the fruit needles, the length, radius, spreading angle of the connecting end, tangential angle of the end and number of the lateral roots, the radius is divided into the maximum radius and the minimum radius.
4. The general modeling method for peanut plants based on the discrete element method according to claim 3, characterized in that: The geometric model of the peanut plant in S2 consists of spherical particles of various conical segments of the stem, spherical particles of the pegs, and spherical particles of various conical segments of the root. The stem includes the main stem and the first branch, and the root includes the main root and the lateral root.
5. A general modeling method for peanut plants based on the discrete element method according to claim 4, characterized in that: The arrangement of the spherical particles in the geometric model of the peanut plant in S2 includes: The arrangement of granules in the main stem, the arrangement of granules in the first branching, the arrangement of granules in the fruit stalks, the arrangement of granules in the main root, and the arrangement of granules in the lateral roots; Both the arrangement of the granules forming the main stem and the arrangement of the granules forming the main root are defined using piecewise linear functions. The arrangement of the first branching sphere, the fruit peg sphere, and the lateral root sphere are all defined by the tangential angle of the line connecting the centers of adjacent spheres. A gradual control method for the change of a cubic function.
6. The general modeling method for peanut plants based on the discrete element method according to claim 5, characterized in that: The specific process of S3 is as follows: S31. Based on the arrangement of the main stem constituent spheres using a piecewise linear function relationship, the coordinates of the main stem constituent spheres are obtained as follows: （1） in, Main stem Within the first conical segment The coordinates of the constituent particles of the sphere Indicates the rapid conical segment of the main stem. This indicates the three gently conical segments of the main stem. , For the first The number of constituent spherical particles within each conical segment. The maximum radius of the main stem The radius step length of the main stem, , The ratio of the minimum radius to the maximum radius within the rapid taper segment of the main stem. Main stem taper segment and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates Main stem taper segment and the first The first component sphere is tangent to the first The radius of each constituent particle of the sphere Main stem The radius of the spherical particles within each tapered section; S32. Based on the arrangement of the principal root constituent spheres using a piecewise linear function relationship, the coordinates of the principal root constituent spheres are obtained as follows: （2） in, The main root Within the first conical segment The coordinates of the constituent particles of the sphere Indicates the rapid conical segment of the primary root. This indicates the two gently tapering segments of the primary root. , The main root The number of constituent spherical particles within each conical segment. The maximum radius of the principal root. The radius step size of the principal root. , The ratio of the minimum radius to the maximum radius within the rapid conic section of the principal root. The main root The radius of the spherical particles within each gently tapered segment The main root taper segment and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates The main root taper segment and the first The first component sphere is tangent to the first The radius of each constituent particle; S33, Based on the tangential angle of the line connecting the centers of adjacent constituent spherical particles. The gradual control method based on cubic function variation defines the arrangement of spherical particles in the first branch, the arrangement of spherical particles in the fruit needle, and the arrangement of spherical particles in the lateral root. The tangential angle is also defined. The function is: （3） in, Indicates multiplication. For the first branch or fruit needle or lateral root , For the first branch Within the first gentle conical transition segment The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. For the first Root fruit needle inside The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. For the first Root lateral root inner first The constituent spherical particles and the first The tangential angle of the line connecting the centers of the constituent spherical particles. , The spreading angle of the first branching point, fruit bud, or lateral root connection point. The tangential angle at the non-connecting end of the first branch, fruit peg, or lateral root. The angle step size factor, , , The number of constituent granules of the first branch, fruit stalk, or lateral root; Based on the radius of the constituent spheres of the first branch, fruit needle, or lateral root and equation (3), the local coordinates of the first branch, fruit needle, or lateral root are obtained: （4） in, For the first branch Within the first gentle conical transition segment The coordinates of the constituent particles of the sphere For the first Root fruit needle inside The coordinates of the constituent particles of the sphere For the first Root lateral root inner first The coordinates of the constituent particles of the sphere On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first The radius of each constituent particle of the sphere For the first branch Within the first gentle conical transition segment The radius of each constituent particle of the sphere For the first Root fruit needle inside The radius of each constituent particle of the sphere For the first Roots and lateral roots Inner The radius of each constituent particle of the sphere Indicates multiplication. On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates; According to equation (4), the global coordinates of the first branch, fruit needle, or lateral root are: （5） in, Indicates local coordinates around The rotation transformation matrix for counterclockwise rotation of the axis. Indicates multiplication.
7. A general modeling method for peanut plants based on the discrete element method according to claim 6, characterized in that: The number, radius, and composition of the spherical particles in each conical segment of the main stem in S31 are described. The axis coordinates are as follows: Let the length of each conical segment of the main stem be equal to the length of the main stem. The ratios are respectively , , , ,but: Number of constituent spheres within the rapid taper segment of the main stem for: （6） in, The length of the rapid taper segment of the main stem; The radius of the constituent spherical particles within the rapid taper segment of the main stem is expressed as: （7） in, The first rapid conical segment of the main stem The radius of each constituent particle; The constituent granules within the rapid taper segment of the main stem The axis coordinates are: （8） in, The first rapid conical segment of the main stem Each of the constituent spherical particles Axis coordinates; The radii and number of constituent granules within the three gently conical segments 2, 3, and 4 of the main stem are as follows: （9） （10） in, The minimum radius of the main stem. The length of the tapered transition segment 2, The length of the tapered transition segment 3, The length of the tapered transition section 4; The main stem has three gently conical segments, 2, 3, and 4, which together form granular structures. The axis coordinates are represented as: （11） in, Main stem Within the first gentle conical transition segment Each of the constituent spherical particles Axis coordinates.
8. A general modeling method for peanut plants based on the discrete element method according to claim 7, characterized in that: The radius and number of the spherical particles formed by the conical segments of the main root in S32 are... The axis coordinates are as follows: Let the lengths of each conical segment of the principal root be equal to the length of the principal root. The ratios are respectively , , ,but: Number of constituent spheres within the rapid taper segment of the main root for: （12） in, The length of the rapid conic section of the principal root; The radius of the constituent spherical particles within the rapid taper segment of the main root is expressed as: （13） in, The first segment within the rapid conical transformation of the main root The radius of each constituent particle; The constituent spherical particles within the rapid taper segment of the main root The axis coordinates are: （14） in, The first segment within the rapid conical transformation of the main root Each of the constituent spherical particles Axis coordinates; The radii and number of constituent spheres within the two gently conical segments 2 and 3 of the main root are as follows: （15） （16） in, The minimum radius of the principal root. The length of the tapered transition segment 2, The length of the tapered transition section 3; The main root has two gently conical segments, 2 and 3, which together form spherical granules. The axis coordinates are represented as: （17） in, The main root Within the first gentle conical transition segment Each of the constituent spherical particles Axis coordinates.
9. A general modeling method for peanut plants based on the discrete element method according to claim 1, characterized in that: The radii and number of spherical particles formed by the first branching of each gently conical segment in S33 are as follows: （18） （19） in, For the first branch The radius of the spherical particles within each conical segment This indicates the three gently conical segments that form the first branch. The maximum radius of the first branch. Let be the minimum radius of the first branch. For the first The number of constituent spherical particles in each tapered segment The length of the first branch; The first branching forms spherical particles The axis coordinates are: （20） in, For the first branch Within the first gentle conical transition segment Each of the constituent spherical particles Axis coordinates On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first Each of the constituent spherical particles Axis coordinates On the first branch or fruit peg or lateral root, and the first The first component sphere is tangent to the first The radius of each constituent particle of the sphere For the first branch Within the first gentle conical transition segment The radius of each constituent particle of the sphere Indicates multiplication; The number of spheres composed of each fruit needle for: （21） in, The length of each fruit needle, The radius of each fruit needle; The number of granules formed by each lateral root for: （22） in, The radius of a spherical particle composed of a single lateral root. The length of a single lateral root. Indicates multiplication. This indicates the classification of lateral roots by level. , Total number of lateral roots: （23） The fruit needles and lateral roots form a ball-like granule. The axis coordinates are: （24） （25） in, For the first The first fruit needle Each of the constituent spherical particles Axis coordinates For the first The first lateral root Each of the constituent spherical particles Axis coordinates For the first Root fruit needle inside The radius of each constituent particle of the sphere For the first Root lateral root inner first The radius of each constituent particle of the sphere Indicates multiplication; The rotation angle of the first branching, fruit bud, or lateral root is expressed as: （26） in, For the first branch or fruit needle or lateral root , Indicates the first branching, fruit bud, or lateral root. Level 1 Branch or first Root wrapping The angle of counterclockwise rotation of the axis, , Indicates the first branching, fruit bud, or lateral root. The number of branches or roots at each level. This indicates the total number of the first branching, fruit pegs, or lateral roots.
10. A general modeling method for peanut plants based on the discrete element method according to claim 1, characterized in that: The specific process of S5 is as follows: The contact mechanical parameters include the impact recovery coefficient. static friction coefficient and rolling friction coefficient Based on a geometric model of peanut plants, the coefficient of restitution for collisions was determined using a drop-bounce method and a high-speed camera. The static friction coefficient was determined using the inclined plane method. and rolling friction coefficient ; Tensile and shear tests were conducted on peanut plants using a universal testing machine, and load-displacement curves were recorded simultaneously to obtain the adhesive mechanical parameters of various parts of the peanut plant. These parameters included the adhesive stiffness coefficient and adhesive strength. The adhesive stiffness coefficient included the normal stiffness per unit area. and tangential stiffness per unit area Bond strength includes normal strength and tangential strength .