Grain threshing simulation method based on discrete elements
Through the discrete element-based grain threshing simulation method, numerical simulation simulation is carried out using five-point sampling method and three-dimensional modeling, which solves the problem that traditional experimental methods are difficult to study the grain threshing process, and achieves efficient and low-cost research results.
Patent Information
- Application Number
- CN202411123021.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-15
- Publication Date
- 2024-12-10
AI Technical Summary
The traditional grain threshing test method is difficult to directly observe the internal structure and relationship of the system, which leads to research difficulties and is affected by environmental factors, making the manufacturing cost and low efficiency.
The grain threshing simulation method based on discrete elements is used to simulate and simulate through five-point sampling method, measuring component parameters, establishing a three-dimensional model, and import discrete element software, setting contact and mechanical parameters, and numerical simulation of the grain threshing process is carried out.
It realizes efficient and low-cost grain threshing research, obtains the working performance and mechanism of the threshing device, avoids difficulties in field and indoor experiments, and has high repeatability and analyticity.
Smart Images
Figure CN119106594A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of grain harvesting, and in particular to a grain threshing simulation method based on a discrete element method. Background Art
[0002] The traditional threshing test method is a sealed dark box structure, and the threshing process inside it is difficult to observe directly, and it is impossible to further study the interaction between grains and threshing elements. Therefore, when studying grain threshing, the internal structure and relationship of the system are not involved, and the system laws are only understood from the general results. This is a black box theory. Data is not easy to obtain during field machine tests; indoor bench tests are labor-intensive and have high manufacturing costs; at the same time, they are affected by various environmental factors such as harvest time and weather, which brings inconvenience to the development of key technologies and equipment for efficient and low-loss grain harvesting. Summary of the invention
[0003] In view of the defects of the prior art, the purpose of the present invention is to provide a grain threshing simulation method based on discrete elements, break the time and space limitations, reduce research costs, and further reveal the grain threshing mechanism.
[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a grain threshing simulation method based on discrete elements, characterized in that it includes the following steps: S1: Select a certain amount of grain materials according to the five-point sampling method, and then enter step S2; S2: measuring the parameters of the components of the cereal material, the components of the cereal material include the grains, cobs, stalks and the number of grains per ear, parameterizing the information of the components of the cereal material, and then entering step S3; S3: Establishing a three-dimensional geometric model of the grain plant in a three-dimensional modeling software, and then proceeding to step S4; S4: importing the three-dimensional model of the threshing device into the discrete element software, setting the motion conditions and the first contact model, and then entering step S5; S5: importing the three-dimensional geometric model of the grain plant into the discrete element software, filling the grain plant model with spherical or cylindrical particles based on the Euclidean distance formula, and then entering step S6; S6: setting a second contact model and a third contact model in the discrete element software, wherein the second contact model defines the connection force between the stalks, cobs, and grains in the cereal material components, and the third contact model defines the wet material characteristics caused by the high moisture content of the cereal material, and then proceeding to step S7; S7: setting contact parameters and mechanical parameters in discrete element software, performing grain threshing simulation, and then proceeding to step S8; S8: performing an actual grain threshing test based on the grain material obtained in step S1, and then proceeding to step S9; S9: Compare the simulation result of step S7 and the test result of step S8, and then proceed to step S10; S10: If the error between the simulation result and the test result is large, proceed to step S7 to reset the contact parameters and mechanical parameters until the simulation result is consistent with the test result, and then save the discrete element simulation model of grain threshing during the harvest period.
[0005] As a preferred scheme, in step S2, measuring the grains includes measuring the grain size, which includes the length, width and height of the grains; measuring the cob includes measuring the cob size, which includes the diameter and length of the cob; measuring the stalks includes measuring the stalk size, which includes the diameter and length of the stalks.
[0006] As a preferred solution, in step S2, measuring the grains also includes measuring the density, Poisson's ratio, and elastic modulus of the grains, and measuring the stems also includes measuring the density, Poisson's ratio, and elastic modulus of the stems.
[0007] As a preferred solution, in step S4, the first contact model defines the energy transfer mode between the grain material and the threshing device, and the first contact model adopts the Hertz-Mindlin no slip model.
[0008] As a preferred solution, in step S6, the second contact model adopts the Hertz-Mindlin with Bonding model, and the third contact model adopts the Hertz-Mindlin with JKR model.
[0009] As a preferred solution, in step S7, the contact parameters include: The coefficient of restitution, static friction and rolling friction between grains; The coefficient of restitution, static friction and rolling friction between the grain and the threshing device; Coefficient of restitution, static friction and rolling friction between stems; The coefficient of restitution, static friction and rolling friction between the stalk and the threshing device.
[0010] As a preferred solution, in step S7, the mechanical parameters include: Normal and shear strength between kernel and cob; Normal strength and shear strength between cobs; Normal and shear strength between stalk and cob; Normal strength and shear strength between stems.
[0011] As a preferred solution, in step S9, the parameters for comparing the simulation results and the test results include impurity content, loss rate and grain distribution pattern.
[0012] The beneficial effects of the present application are as follows: the present invention realizes numerical simulation of the grain threshing process through discrete element software, and provides a method for obtaining and verifying the working performance of the threshing device; the method can obtain the impurity content and loss rate of the threshed material, and at the same time can obtain the movement time and load history of the grain in the threshing device, and provide theoretical support for exploring the grain threshing mechanism and the interaction mechanism between the grain and the threshing device. The simulation method of the present invention can avoid the trouble of collecting data in field harvesting tests and preparing materials for indoor bench tests, and has the advantages of not being restricted by time and space, high repeatability, strong analyzability, high efficiency, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 The schematic diagram for constructing the wheat ear model for this application;
[0014] Figure 2 Schematic diagram for building the wheat stalk model for this application;
[0015] Figure 3 For this application, a discrete element model of wheat plants was developed;
[0016] Figure 4 Schematic diagram of wheat plant connection for this application;
[0017] Figure 5 This is the time-load history diagram of the wheat threshing process in this application;
[0018] Figure 6 The maximum impact force and friction force on wheat threshing in this application;
[0019] Figure 7 This is a diagram showing the axial distribution of materials at the bottom of the threshing device for this application. DETAILED DESCRIPTION
[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0021] The present invention will use the restoration of the wheat threshing process of the single longitudinal axial flow threshing device to complete the analysis of its threshing phenomenon, threshing load and working performance as an implementation case to provide a clear and complete description. The present invention simulates the wheat threshing process based on EDEM software.
[0022] Combination Figure 1-Figure 7 The present application provides a grain threshing simulation method based on discrete elements, comprising the following steps:
[0023] S1: 35 kg of freshly harvested wheat plants were selected according to the five-point sampling method.
[0024] S2: Measure wheat plant component parameters, which include grains, spike cobs, stalks and the number of grains per spike. Parameterize the wheat plant component information and then proceed to step S3.
[0025] In step S2, measuring the grain includes measuring the grain size, the grain size includes the length, width and height of the grain, measuring the cob includes measuring the cob size, the cob size includes the diameter and length of the cob, and measuring the stalk includes measuring the stalk size, the stalk size includes the diameter and length of the stalk. Measuring the grain also includes measuring the density, Poisson's ratio and elastic modulus of the grain, and measuring the stalk also includes measuring the density, Poisson's ratio and elastic modulus of the stalk. In this embodiment, the cereal material is a wheat plant.
[0026] Measuring the wheat plant component parameters includes measuring the length, width and height of wheat grains, measuring the diameter and length of wheat cobs, measuring the diameter and length of wheat stalks, measuring the density, Poisson's ratio and elastic modulus of wheat grains, and measuring the density, Poisson's ratio and elastic modulus of wheat stalks. Table 1 below shows the main physical parameters of the wheat plants obtained by measurement.
[0027] Table 1 Physical parameters of wheat plants
[0028] S3: According to the physical parameters of the wheat plant obtained in step S2, a three-dimensional geometric model of the grain plant is established in the three-dimensional modeling software, and then the process proceeds to step S4. The three-dimensional modeling software can adopt existing commonly used three-dimensional modeling software, such as the three-dimensional modeling software solidworks.
[0029] S4: Import the threshing device three-dimensional model into the discrete element software, set the motion conditions and the first contact model, and then enter step S5. The threshing device three-dimensional model adopts the existing single longitudinal axial flow threshing device three-dimensional model. The threshing device motion conditions are the same as the actual motion conditions. In this embodiment, the wheat conveying speed is set to 1.5m / s, 7kg of wheat plants are laid in every 1m of length, the feed amount is controlled to 7kg / s, and the drum speed is set to 800rpm. The first contact model defines the energy transfer between the grain material and the threshing device. The first contact model adopts the Hertz-Mindlin no slip model. In the first contact model, the normal force F n , tangential force F t , Normal damping force and tangential damping force It is defined by the following equation: In the formula, is the equivalent Young's modulus, is the equivalent radius, G * is the equivalent shear modulus, is equivalent mass.
[0030] S5: Import the three-dimensional geometric model of the wheat plant into the discrete element software, fill the wheat plant model with spherical or cylindrical particles in the three-dimensional space based on the Euclidean distance formula, and then enter step S6.
[0031] Given a wheat grain model filling a three-dimensional space and the number of filled grains, solve D in space min (V1,V2)≤R max The process is to realize the three-dimensional Euclidean distance transformation of particle filling.
[0032] The solution process is adjusted according to the following equation. D min (V1,V2)≤R max (6)
[0033] Where D is the distance between any two points V(x,y,z) in space; R max is the maximum inscribed sphere radius relative to the filling space boundary.
[0034] Figure 1 and Figure 2 They are the filling three-dimensional space and construction principle of wheat ears and stalks, Figure 3 It is a discrete element model of wheat plant filled with spherical or cylindrical particle model based on Euclidean method.
[0035] Furthermore, according to the data results in step S2, a basic grain model is generated by using a normal distribution method to characterize the differential effects of natural selection on wheat shape.
[0036] S6: Set the second contact model and the third contact model in the discrete element software. The second contact model defines the connection force between the stalks, cobs, and grains in the cereal material components. The third contact model defines the wet material characteristics caused by the high moisture content of the cereal material, and then enter step S7.
[0037] The second contact model uses the Hertz-Mindlin with Bonding model, and the third contact model uses the Hertz-Mindlin with JKR model. Figure 4 shown.
[0038] The force (F) on the particles after the adjacent particles are combined in the wheat plant model n ,t) and torque (M n ,t) is adjusted at each time step according to the following equation. Where R B is the bonding radius; S n is the normal stiffness; S t is the shear stiffness; δ t is the time step; v n is the normal velocity; v t is the tangential velocity; ω n is the normal acceleration; ω t is the tangential acceleration.
[0039] The connection force failure conditions between wheat stalks, cobs, and kernels were adjusted according to the following equations.
[0040] The additional normal contact force on the wheat plant surface due to moisture can be adjusted using the following equation.
[0041] Where E * is relative elasticity; R * is the relative radius; a is the contact radius; Υ is the surface energy of the two contacting spheres; α is the relative proximity distance of the particles; F nc is the maximum tensile force.
[0042] S7: setting contact parameters and mechanical parameters in discrete element software, performing grain threshing simulation, and then proceeding to step S8. It should be noted that the parts not described in detail in this application are all prior art.
[0043] In step S7, the contact parameters include: the coefficient of restitution, the coefficient of static friction and the coefficient of rolling friction between the seeds; The coefficient of restitution, static friction and rolling friction between the grain and the threshing device; Coefficient of restitution, static friction and rolling friction between stems; The coefficient of restitution, static friction and rolling friction between the stalk and the threshing device. Mechanical parameters include: normal strength and shear strength between kernel and cob; Normal strength and shear strength between cobs; Normal and shear strength between stalk and cob; Normal strength and shear strength between stems.
[0044] The mechanical parameters are obtained through uniaxial compression test, three-point bending test and shear test. The uniaxial compression test, three-point bending test and shear test are existing test technologies and will not be described in detail in this application.
[0045] The contact parameters are obtained through ramp test and drop test. Both ramp test and drop test are existing test technologies and will not be described in detail in this application.
[0046] Table 2 shows the contact parameters of wheat plants used in the present invention; Table 3 shows the mechanical parameters of wheat plants used in the present invention.
[0047] Table 2 Wheat plant contact parameters
[0048] Table 3 Mechanical parameters of wheat plants
[0049] Furthermore, after the simulation is completed, the simulation phenomena and simulation results are post-processed and analyzed. Figure 5 is the time-load spectrum of the load on wheat during threshing, Figure 6 The maximum impact and friction force on wheat threshing. Figure 7 This is the axial distribution law of the material at the bottom of the threshing device after threshing is completed.
[0050] S8: Based on the wheat plants obtained in step S1, an actual wheat threshing test is performed, the feed amount, the drum speed and the mechanical structure are controlled to be the same as the simulation conditions, and then step S9 is entered.
[0051] S9: Compare the simulation results of step S7 and the test results of step S8, and then proceed to step S10. The comparison results of the test and simulation of this case are shown in Table 4. Table 4 Comparative analysis of experimental and simulation results
[0052] S10: If the error between the simulation result and the test result is large, proceed to step S7 to reset the contact parameters and mechanical parameters until the simulation result is consistent with the test result, and then save the discrete element simulation model of wheat threshing during the harvest period.
[0053] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.
Claims
1. A grain threshing simulation method based on discrete elements, characterized in that: The steps include: S1: Select a certain amount of grain materials according to the five-point sampling method, and then enter step S2; S2: measuring the parameters of the components of the cereal material, the components of the cereal material include the grains, cobs, stalks and the number of grains per ear, parameterizing the information of the components of the cereal material, and then entering step S3; S3: Establishing a three-dimensional geometric model of the grain plant in a three-dimensional modeling software, and then proceeding to step S4; S4: importing the three-dimensional model of the threshing device into the discrete element software, setting the motion conditions and the first contact model, and then entering step S5; S5: importing the three-dimensional geometric model of the grain plant into the discrete element software, filling the grain plant model with spherical or cylindrical particles based on the Euclidean distance formula, and then entering step S6; S6: setting a second contact model and a third contact model in the discrete element software, wherein the second contact model defines the connection force between the stalks, cobs, and grains in the cereal material components, and the third contact model defines the wet material characteristics caused by the high moisture content of the cereal material, and then proceeding to step S7; S7: setting contact parameters and mechanical parameters in discrete element software, performing grain threshing simulation, and then proceeding to step S8; S8: performing an actual grain threshing test based on the grain material obtained in step S1, and then proceeding to step S9; S9: Compare the simulation result of step S7 and the test result of step S8, and then proceed to step S10; S10: If the error between the simulation result and the test result is large, proceed to step S7 to reset the contact parameters and mechanical parameters until the simulation result is consistent with the test result, and then save the discrete element simulation model of grain threshing during the harvest period.
2. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S2, measuring the grains includes measuring the grain size, which includes the length, width and height of the grains; measuring the cobs includes measuring the cob size, which includes the diameter and length of the cobs; and measuring the stalks includes measuring the stalk size, which includes the diameter and length of the stalks.
3. The method for constructing a discrete element simulation model of a cereal material according to claim 2, characterized in that: In step S2, measuring the grains also includes measuring the density, Poisson's ratio, and elastic modulus of the grains, and measuring the stems also includes measuring the density, Poisson's ratio, and elastic modulus of the stems.
4. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S4, the first contact model defines the energy transfer mode between the grain material and the threshing device, and the first contact model adopts the Hertz-Mindlin no slip model.
5. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S6, the second contact model adopts the Hertz-Mindlin with Bonding model, and the third contact model adopts the Hertz-Mindlin with JKR model.
6. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S7, the contact parameters include: The coefficient of restitution, static friction and rolling friction between grains; The coefficient of restitution, static friction and rolling friction between the grain and the threshing device; Coefficient of restitution, static friction and rolling friction between stems; The coefficient of restitution, static friction and rolling friction between the stalk and the threshing device.
7. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S7, the mechanical parameters include: Normal and shear strength between kernel and cob; Normal strength and shear strength between cobs; Normal and shear strength between stalk and cob; Normal strength and shear strength between stems.
8. The method for constructing a discrete element simulation model of a cereal material according to claim 1, characterized in that: In step S9, the parameters for comparing the simulation results and the test results include the impurity content, loss rate and grain distribution pattern.