Modeling method for evaluating the effect of the barycenter position on the natural frequency of a peduncle system

Abstract

The application discloses a model construction method for evaluating the influence of the center of gravity position on the inherent frequency of a pedicel-fruit system, and comprises the following steps: selecting a certain number of pedicel-fruit system samples, testing the mean values of various physical parameters, drawing the half-edge profile of the fruit in two-dimensional software, importing the half-edge profile of the fruit into three-dimensional software, rotating the half-edge profile by 270 degrees and 90 degrees respectively to obtain two fruit entities, fruit I and fruit II, which constitute the fruit, obtaining the corresponding relationship between the center of gravity deviation rate and the densities of fruit I and fruit II, obtaining the corresponding relationship between the densities of fruit I and fruit II and the inherent frequency of the pedicel-fruit system through finite element modal analysis, and obtaining the corresponding relationship between the center of gravity deviation rate and the inherent frequency of the pedicel-fruit system according to the corresponding relationship between the center of gravity deviation rate and the densities of fruit I and fruit II and the corresponding relationship between the densities of fruit I and fruit II and the inherent frequency of the pedicel-fruit system. By introducing the center of gravity deviation rate as a parameter, the application can more comprehensively and accurately evaluate the influence of the center of gravity position on the inherent frequency of the pedicel-fruit system.

Description

Technical Field

[0001] This invention belongs to the field of fruit tree harvesting in agriculture and forestry, specifically a model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system. Background Technology

[0002] In the vibration harvesting process of forest fruits, the natural frequencies of the peduncle system largely determine its motion response under forced vibration, thus affecting fruit drop. To better understand and optimize the vibration harvesting process, studying the influence of the natural frequencies of the peduncle system is crucial. Regardless of the type of forest fruit crop, fruit growth exhibits a degree of randomness, resulting in a non-perfectly symmetrical fruit shape. This asymmetry affects the vibration characteristics of the peduncle system. For example, differences in fruit shape, pit position, and weight can alter the mass distribution of the peduncle system, causing the center of gravity to be somewhat random and often not at the ideal position along the system's centerline. This, in turn, changes the system's moment of inertia and stiffness, thus affecting its natural frequencies. Although some scholars both domestically and internationally have established models to study the natural frequencies of the peduncle system, none of these models have considered the influence of the center of gravity position. To better understand the modal characteristics of the peduncle system's vibration, it is necessary to investigate the extent to which the randomness of the center of gravity position affects its natural frequencies. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system, which addresses the shortcomings of the prior art. This method, by introducing the center of gravity deviation rate as a parameter, can more comprehensively and accurately evaluate the influence of the center of gravity position on the natural frequency of the peduncle system.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0005] A model-building method for evaluating the influence of the center of gravity location on the intrinsic frequency of a stalk-fruit system includes:

[0006] Step 1: Select a certain number of peduncle system samples, test the mean values ​​of their various physical parameters, and calculate the mean density of the fruit.

[0007] Step 2: Draw half of the fruit's outline in 2D software using image outlining. Adjust the size of the half of the fruit's outline according to the average values ​​of the physical parameters obtained in Step 1.

[0008] Step 3: Import half of the fruit's outline into the 3D software, and rotate it along the fruit's central longitudinal axis by 270 degrees and 90 degrees respectively to obtain two solid parts that make up the fruit. The solid part obtained by rotating 270 degrees is denoted as Fruit I, and the solid part obtained by rotating 90 degrees is denoted as Fruit II. Assemble Fruit I and Fruit II together to form a solid model of the fruit with a completely centrally symmetrical shape. Draw the solid model of the fruit branch and the solid model of the fruit stalk based on the average values ​​of the physical parameters obtained from the test in Step 1.

[0009] Step 4: In the 3D software, set multiple sets of density parameters for Fruit I and Fruit II. The set condition is 0.75 * density of Fruit I + 0.25 * density of Fruit II = mean density of the fruit. The mean density of the fruit is calculated in Step 1 and remains constant. Obtain the center of gravity position of the fruit under each set of density parameters for Fruit I and Fruit II. Calculate the center of gravity deviation rate based on the center of gravity position of the fruit to obtain the correspondence between the center of gravity deviation rate and the density of Fruit I and Fruit II.

[0010] Step 5: The fruit solid model, fruit branch solid model and fruit pedicel solid model are combined to form a three-dimensional model of the fruit-pedicel system. The three-dimensional model of the fruit-pedicel system is imported into the finite element analysis software and meshed. The meshes of the fruit part, fruit branch part and fruit pedicel part in the fruit-pedicel system are connected by sharing nodes to obtain the mesh model of the fruit-pedicel system.

[0011] Step 6: In the finite element analysis software, set the material parameters of the model according to the average values ​​of the physical parameters obtained in Step 1, constrain the displacement and rotation of the fruit branches, and perform finite element modal analysis; among them, the density of Fruit I and the density of Fruit II are set as random parameters, and the correspondence between the density of Fruit I and the density of Fruit II and the natural frequency of the peduncle system is obtained through finite element modal analysis.

[0012] Step 7: Based on the correspondence between the center of gravity deviation rate and the density of fruit I and fruit II, and the correspondence between the density of fruit I and fruit II and the natural frequency of the peduncle-fruit system, the correspondence between the center of gravity deviation rate and the natural frequency of the peduncle-fruit system is obtained.

[0013] As a further improvement of the present invention, in step 1, the physical parameters include the size of the fruit branch, the size of the fruit stalk, the mass of the fruit stalk, the elastic modulus of the fruit stalk, the transverse diameter of the fruit, the longitudinal diameter of the fruit, and the mass of the fruit; the average density of the fruit branch, the average density of the fruit stalk, and the average density of the fruit are calculated respectively.

[0014] As a further improvement of the present invention, in step 2, half of the fruit's outline is drawn in CAD software by tracing the image, and the size of the half of the fruit's outline is adjusted according to the average value of the fruit's transverse diameter and the average value of the fruit's longitudinal diameter obtained in step 1.

[0015] As a further improvement of the present invention, in step 3, the three-dimensional software is Solidworks software; the fruit branch solid model is drawn based on the average size of the fruit branch obtained from step 1, and the fruit stalk solid model is drawn based on the average size of the fruit stalk obtained from step 1.

[0016] As a further improvement of the present invention, in step 4, the centroid assessment function of Solidworks software is used to obtain the centroid position of the fruit under the density parameters of each group of fruit I and fruit II.

[0017] As a further improvement to the present invention, the calculation of the center of gravity deviation rate based on the center of gravity position of the fruit in step 4 is specifically as follows:

[0018] Calculate the distance c from the center of gravity to the fruit axis, and set the ratio of distance c to the mean of the fruit's transverse diameter obtained in step 1 as the center of gravity deviation rate.

[0019] As a further improvement to the present invention, in step 5, the finite element analysis software is Ansys Workbench.

[0020] As a further improved technical solution of the present invention, in step 6, in the finite element analysis software, the fruit branch and fruit are set as rigid bodies, the fruit stalk is set as an elastic body, the material parameters of the model are set according to the average value of various physical parameters obtained in step 1, the displacement and rotation of the fruit branch are constrained, and finite element modal analysis is performed.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. More accurate assessment of the influence of the natural frequency of the peduncle-fruit system: Traditional peduncle-fruit system natural frequency models do not consider the influence of the randomness of the center of gravity position on the frequency. However, this invention introduces the center of gravity deviation rate as a parameter, which can more comprehensively and accurately assess the influence of the center of gravity position on the natural frequency of the peduncle-fruit system. Therefore, this invention can provide more accurate prediction and analysis results of the natural frequency of the peduncle-fruit system.

[0023] 2. Deeper Understanding of the Vibration Characteristics of the Stalk-Corn System: By considering the randomness of the center of gravity position, this invention provides a clearer understanding of the vibration characteristics of the stalk-corn system. Deviations in the center of gravity position alter the system's moment of inertia and stiffness, thus affecting the system's natural frequencies. Through the modeling method provided by this invention, researchers can gain a deeper understanding of the relationship between the center of gravity position and the natural frequencies, thereby better optimizing the vibration harvesting process.

[0024] In summary, the technical advantage of this invention is that by introducing the randomness of the center of gravity position, its impact on the natural frequency of the peduncle system is comprehensively evaluated. This will contribute to a deeper understanding of the vibration characteristics of the peduncle system and provide a scientific basis for optimizing the vibration harvesting process of forest fruits. Attached Figure Description

[0025] Figure 1 A schematic diagram illustrating the modeling and division of the peduncle system and fruit.

[0026] Figure 2 This is a flowchart illustrating the analysis process of the method of the present invention.

[0027] Figure 3 A diagram illustrating the model building process.

[0028] Figure 4 The graph shows the relationship between the first-order natural frequency of the Ginkgo biloba peduncle system and the centroid offset rate. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0030] This embodiment provides a model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system. The method will be described in detail below using Ginkgo biloba as an example.

[0031] For the forest fruit crops studied, such as ginkgo, a certain number of peduncle-fruit system samples were selected, and the mean values ​​of various physical parameters were tested for model construction. These physical parameters included the external dimensions of fruit branch 1, the external dimensions of peduncle 2, the mass and elastic modulus of peduncle 2, the transverse diameter of fruit 3, the longitudinal diameter of fruit 3, and the mass of fruit 3. The mean density of each part was calculated; in calculating the density, the volume parameter was measured using the displacement method.

[0032] Select a fruit sample with a relatively symmetrical shape and draw half of its outline in CAD software using image outlining. Based on the average of the measured transverse and longitudinal diameters of fruit 3, adjust it to a suitable size and import it into Solidworks software. Rotate the sample along the central longitudinal axis of fruit 3 by 270 degrees and 90 degrees respectively to obtain the two solid parts that make up fruit 3, denoted as fruit I and fruit II. Figure 1 Fruit I and Fruit II are assembled together to form a solid model of a fruit with a completely centrally symmetrical external structure. The solid models of the fruit branches and fruit stalks are drawn based on the average values ​​of their corresponding external dimensions.

[0033] In Solidworks, assign density parameters to fruit I and fruit II, setting multiple sets of density parameters for fruit I and fruit II. The setting condition is: 0.75 * fruit I density + 0.25 * fruit II density = 1.08e-3 kg·m³ -3 1.08e-3kg·m-3 The calculated average density of fruit 3 was kept constant, ensuring that the weight of fruit 3 remained consistently 7.46g. Using the center of gravity assessment function in Solidworks software, the position of the center of gravity of fruit 3 under each set of parameters was obtained. The distance *c* from the axis of fruit 3 was calculated, and its ratio to the average transverse diameter *R* of fruit 3 was set as the center of gravity deviation rate *v*. The correspondence between the center of gravity deviation rate *v* and the densities of fruit I and fruit II was then obtained.

[0034] The fruit solid model, fruit branch solid model, and fruit pedicel solid model constitute a three-dimensional model of the pedicel-fruit system. The three-dimensional model of the pedicel-fruit system is imported into the finite element analysis software Ansys Workbench and meshed. The meshes of each part of the pedicel-fruit system are connected by sharing nodes to obtain the mesh model of the pedicel-fruit system.

[0035] The model building process in this embodiment is as follows: Figure 3 As shown in Table 1, the external shape parameters of the model structure in the 3D model construction are shown in Table 1; the material parameters of the model in the finite element model are shown in Table 2.

[0036] Table 1. External Parameters of the Model Structure (mm):

[0037] 46.30 1.30 2.74 8.02 3.40 27.58 21.7

[0038] Table 2. Model material parameters:

[0039]

[0040] In the finite element analysis software, the displacement and rotation of the constrained fruit branch 1 were analyzed using finite element modal analysis. Considering that the deformation in the forced vibration response of the fruit-stalk system mainly occurs in the stalk portion, fruit branch 1 and fruit 3 were set as rigid bodies in the model, while the stalk 2 was set as an elastic body. The material parameters of the model were set based on the average values ​​obtained in the first step, as shown in Table 2. The density parameters of the two parts of fruit 3, fruit I and fruit II, were set as random parameters. The influence of the densities of fruit I and fruit II on the natural frequencies of the fruit-stalk system was obtained through finite element modal analysis.

[0041] Based on the correspondence between the centroid deviation rate v and the densities of fruit I and fruit II, and the correspondence between the densities of fruit I and fruit II and the natural frequencies of the pedicel-fruit system, the correspondence between the centroid deviation rate v and the natural frequencies of the pedicel-fruit system is obtained, thus realizing the model construction of the influence of the three centroid positions of the fruit on the natural frequencies of the pedicel-fruit system. The analysis process of the method in this embodiment is as follows: Figure 2 As shown. Figure 4 To understand the relationship between the first-order natural frequency of the Ginkgo peduncle system and the centroid offset rate, it can be found that when the centroid offset rate of the Ginkgo fruit varies in the range of 8%-26%, the first-order natural frequency of the Ginkgo single-species system varies in the range of 2.09-2.11 Hz.

[0042] The scope of protection of this invention includes, but is not limited to, the above embodiments. The scope of protection of this invention is defined by the claims. Any substitutions, modifications, or improvements to this technology that are easily conceived by those skilled in the art fall within the scope of protection of this invention.

Claims

1. A model construction method for evaluating the influence of the center of gravity position on the natural frequencies of a stalk-fruit system, characterized in that, include: Step 1: Select a certain number of peduncle system samples, test the mean values ​​of their various physical parameters, and calculate the mean density of the fruit. Step 2: Draw half of the fruit's outline in 2D software by tracing the image. Adjust the size of the half of the fruit's outline according to the average values ​​of the physical parameters obtained in Step 1. Step 3: Import half of the fruit's outline into the 3D software, and rotate it along the fruit's central longitudinal axis by 270 degrees and 90 degrees respectively to obtain two solid parts that make up the fruit. The solid part obtained by rotating 270 degrees is denoted as Fruit I, and the solid part obtained by rotating 90 degrees is denoted as Fruit II. Assemble Fruit I and Fruit II together to form a solid model of the fruit with a completely centrally symmetrical shape. Draw the solid model of the fruit branch and the solid model of the fruit stalk based on the average values ​​of the physical parameters obtained from the test in Step 1. Step 4: In the 3D software, set multiple sets of density parameters for Fruit I and Fruit II. The set condition is 0.75 * density of Fruit I + 0.25 * density of Fruit II = mean density of the fruit. The mean density of the fruit is calculated in Step 1 and remains constant. Obtain the center of gravity position of the fruit under each set of density parameters for Fruit I and Fruit II. Calculate the center of gravity deviation rate based on the center of gravity position of the fruit to obtain the correspondence between the center of gravity deviation rate and the density of Fruit I and Fruit II. Step 5: Assemble the fruit solid model, fruit branch solid model and fruit stalk solid model into a three-dimensional model of the fruit-stalk system. Import the three-dimensional model of the fruit-stalk system into the finite element analysis software and generate a mesh. Connect the fruit part mesh, fruit branch part mesh and fruit stalk part mesh in the fruit-stalk system with common nodes to obtain the fruit-stalk system mesh model. Step 6: In the finite element analysis software, set the material parameters of the model according to the average values ​​of the physical parameters obtained in Step 1, constrain the displacement and rotation of the fruit branches, and perform finite element modal analysis; among them, the density of Fruit I and the density of Fruit II are set as random parameters, and the correspondence between the density of Fruit I and the density of Fruit II and the natural frequency of the peduncle system is obtained through finite element modal analysis. Step 7: Based on the correspondence between the center of gravity deviation rate and the density of fruit I and fruit II, and the correspondence between the density of fruit I and fruit II and the natural frequency of the peduncle-fruit system, the correspondence between the center of gravity deviation rate and the natural frequency of the peduncle-fruit system is obtained.

2. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 1, characterized in that, In step 1, the physical parameters include the size of the fruit branch, the size of the fruit stalk, the mass of the fruit stalk, the elastic modulus of the fruit stalk, the transverse diameter of the fruit, the longitudinal diameter of the fruit, and the mass of the fruit; the average density of the fruit branch, the average density of the fruit stalk, and the average density of the fruit are calculated respectively.

3. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 2, characterized in that, In step 2, half of the fruit's outline is drawn in CAD software by tracing the image. The size of the half of the fruit's outline is adjusted according to the average values ​​of the fruit's transverse diameter and longitudinal diameter obtained in step 1.

4. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 2, characterized in that, In step 3, the 3D software is Solidworks software; the fruit branch solid model is drawn based on the average size of the fruit branch obtained from step 1, and the fruit stalk solid model is drawn based on the average size of the fruit stalk obtained from step 1.

5. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 4, characterized in that, In step 4, the centroid assessment function of Solidworks software is used to obtain the centroid position of the fruit under the density parameters of each group of fruit I and fruit II.

6. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 5, characterized in that, The calculation of the center of gravity deviation rate based on the fruit's center of gravity position in step 4 is specifically as follows: Calculate the distance c from the center of gravity to the fruit axis, and set the ratio of distance c to the mean of the fruit's transverse diameter obtained in step 1 as the center of gravity deviation rate.

7. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 1, characterized in that, In step 5, the finite element analysis software used is Ansys Workbench.

8. The model construction method for evaluating the influence of the center of gravity position on the natural frequency of the peduncle system according to claim 1, characterized in that, In step 6, in the finite element analysis software, the fruit branches and fruits are set as rigid bodies, and the fruit stalk is set as an elastic body. The material parameters of the model are set according to the average values ​​of the physical parameters obtained from the test in step 1, and the displacement and rotation of the fruit branches are constrained to perform finite element modal analysis.

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