Agricultural material collision mechanics characteristic determination test bed and collision model establishment method

Abstract

The application discloses a kind of agricultural material collision mechanics characteristic determination test bench and collision model establishment method, test bench includes wooden swing arm and material base, wooden swing arm one end is fixed on shaft, other end installs force sensor and impact head, shaft one end passes through bearing seat, other end is connected with angle encoder, bearing seat and angle encoder are all fixed;Material base is placed agricultural material, and when wooden swing arm is in vertical position, impact head is just in contact with agricultural material;Iron sheet is connected in the middle of wooden swing arm, iron sheet is attracted by unpowered electromagnetic switch, electromagnetic switch is adjustably installed on connecting piece, and angle adjusting disc is fixed at both ends of connecting piece respectively.The test bench can obtain the relationship between deformation and pressure generated by agricultural material collision under different working conditions, and collision modeling is carried out using the obtained collision force and deformation.The application can truly simulate the mechanical change generated by agricultural material collision.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of agricultural engineering, and particularly relates to a kind of agricultural material collision mechanics characteristic determination test bed and collision model establishment method. BACKGROUND

[0002] At present, there are related equipment for potato, apple and other agricultural materials in harvesting, cleaning, grading and other links, but the existing sorting assembly line, packaging and storage and transportation machinery are mainly designed based on the experience of engineering and technical personnel, and the developed related tools are easy to cause secondary damage to fruits.According to the investigation, the annual loss of potato, apple and other agricultural materials due to mechanical damage during harvesting, cleaning, grading and storage into warehouse is large, which causes great economic loss.

[0003] Establishing agricultural material-machine interaction model, predicting the collision mechanics process of agricultural material and machine under different working conditions, and then taking relevant measures are effective measures to reduce mechanical damage.The existing research mainly simulates the process of fruit collision by (quasi-) static test, and the existing contact mechanics model is mainly based on pure elastic or pure plastic deformation, lacking the dynamic loading process between agricultural material and mechanical device and the accurate characterization of viscoelastic plastic process state. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides an agricultural material collision mechanics characteristic determination test bed and a collision model establishment method, which can accurately characterize the dynamic process of agricultural material collision.

[0005] The present application achieves the above technical objectives through the following technical means.

[0006] An agricultural material collision mechanics characteristic determination test bed, comprising:

[0007] A wooden swing arm, one end of which is fixed on a shaft, and the other end is provided with a force sensor; an impact head is installed on the force sensor; one end of the shaft penetrates through a bearing seat, and the other end is connected with an angle encoder, and the bearing seat and the angle encoder are both fixed;

[0008] A material base, on which agricultural materials are placed, and when the wooden swing arm is in a vertical position, the impact head is in contact with the agricultural materials;

[0009] An iron sheet is connected at the middle position of the wooden swing arm, and the iron sheet is attracted by an unpowered electromagnetic switch, the electromagnetic switch is adjustably installed on a connecting piece through a connecting rod, and the connecting piece is fixed with angle adjusting discs at both ends;

[0010] The force sensor, the angle encoder and the electromagnetic switch all communicate with a digital signal processing experiment box, and the digital signal processing experiment box is connected with a computer.

[0011] In the technical solution, the material base is fixed at one end of the aluminum profile II, the other end of the aluminum profile II is fixed perpendicularly to the aluminum profile I, and the aluminum profile I is fixed on the bottom plate.

[0012] In the technical solution, the aluminum profile II is fixed at the middle position of the bottom plate through the square base.

[0013] In the technical solution, the symmetrically fixed support I and support II are fixed on the bottom plate, the rectangular support is fixed on the upper part of the support I and support II, and the bearing seat and angle encoder are fixed on the rectangular support.

[0014] In the technical solution, the angle adjusting disc is fixed on the support I and support II.

[0015] In the technical solution, the agricultural material includes but is not limited to rice stalks, wheat stalks, apples, potatoes, and citrus fruits.

[0016] In the technical solution, for the stalk-type agricultural material, the shape of the impact head is T-shaped, and the shape of the end of the material base is similar to V-shaped.

[0017] In the technical solution, for the apple, potato, and citrus-type agricultural material, the shape of the impact head is spherical, and the material base is L-shaped.

[0018] A collision model establishment method based on an agricultural material collision mechanics characteristic determination test bench, when the agricultural material is a potato, the established collision model is:

[0019]

[0020] Wherein: E* is the equivalent elastic modulus of two colliding bodies, R * is the equivalent curvature radius of two colliding bodies, δ represents the deformation of two colliding bodies in contact, represents the deformation rate of two colliding bodies in contact, A * represents the equivalent dissipation constant, K h is the Hertz stiffness, K y is the linear stiffness in the elastic loading stage, δ y represents the yield point of the agricultural material, δ m represents the maximum deformation of two colliding bodies in contact, F * is the collision force.

[0021] The beneficial effects of the present application are:

[0022] (1) The test bench of the application can simulate the mechanical changes of agricultural materials caused by collision, has certain reference value for the collision of agricultural materials with various parts in the harvesting, cleaning, storage and transportation process, and solves the problem of difficulty in analyzing the mechanical properties of agricultural materials in a non-field experimental environment, which is of great significance for the design optimization of harvesters and sorting machines.

[0023] (2) The collision model of the application can prepare a dynamic process representing the collision of agricultural materials, and lay a foundation for subsequent establishment of discrete element or finite element models to predict mechanical damage of fruits. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a side view of the agricultural material collision mechanics property measuring test bench described in the application;

[0025] Figure 2 is a front view of the agricultural material collision mechanics property measuring test bench described in the application;

[0026] Figure 3 is a stress and deformation curve diagram of potatoes in the compression mechanics property experiment described in the application;

[0027] Figure 4 is a Hertz theory equivalent elastic modulus fitting curve diagram of potatoes described in the application;

[0028] Figure 5 is a comparison diagram of three models and measured curves;

[0029] Figure 6 is a fitting degree diagram of three models described in the application;

[0030] In the figure: 1-bottom plate, 2-aluminum profile I, 3-aluminum profile II, 4-bracket I, 5-bracket II, 6-impact head, 7-force sensor, 8-sensor base, 9-wooden swing arm, 10-angle encoder, 11-digital signal processing experiment box, 12-rectangular bracket, 13-material base, 14-fixing part I, 15-fixing part II, 16-shaft, 17-bearing seat, 18-angle adjusting disc I, 19-angle adjusting disc II, 20-magnetic switch, 21-iron sheet, 22-connector, 23-square base. DETAILED DESCRIPTION

[0031] The application will be further described below in combination with the drawings and specific embodiments, but the protection scope of the application is not limited thereto.

[0032] As Figure 1 , 2As shown in the figure, an agricultural material collision mechanics property determination test bench comprises a base plate 1, an aluminum profile I 2, an aluminum profile II 3, a support I 4, a support II 5, an impact head 6, a force sensor 7, a sensor base 8, a wooden swing arm 9, an angle encoder 10, a digital signal processing experiment box 11, a rectangular support 12, a material base 13, a fixing part I 14, a fixing part II 15, a shaft 16, a bearing seat 17, an angle adjusting disc I 18, an angle adjusting disc II 19, an electromagnetic switch 20, an iron sheet 21, a connecting part 22 and a square base 23.

[0033] The support I 4 and the support II 5 are symmetrically welded and fixed on the base plate 1 and constitute a main structure of the test bench; the aluminum profile I 2 is fixed on the base plate 1 by bolts, one end of the aluminum profile II 3 is fixed perpendicularly to the aluminum profile I 2 by bolts, the aluminum profile II 3 is fixed at a middle position thereof on the square base 23 by bolts, the square base 23 is fixed on the base plate 1 by bolts, the material base 13 is fixed on the other end of the aluminum profile II 3 by bolts, and the material base 13 can be adjusted within a range of 0-20 mm along a length direction of the aluminum profile II 3.

[0034] One end of the wooden swing arm 9 is inserted into a middle position of the shaft 16 and is fixed by the fixing part I 14 and the fixing part II 15, one end of the shaft 16 passes through the bearing seat 17 and the other end is connected to the angle encoder 10, the bearing seat 17 and the angle encoder 10 are fixed on the rectangular support 12 respectively, and the rectangular support 12 is welded on upper portions of the support I 4 and the support II 5; the force sensor 7 is installed on the sensor base 8 at the other end of the wooden swing arm 9, and the impact head 6 is installed on the force sensor 7; the iron sheet 21 is connected to a middle position of the wooden swing arm 9 by bolts, the iron sheet 21 is attracted by the unpowered electromagnetic switch 20, the electromagnetic switch 20 is fixed on one end of a connecting rod, the other end of the connecting rod is inserted into a through hole in the middle of the connecting part 22 and is fixed by a nut, the connecting part 22 is in a U shape, two ends thereof are fixed with the angle adjusting disc I 18 and the angle adjusting disc II 19 by nuts respectively, and the angle adjusting disc I 18 and the angle adjusting disc II 19 are fixed on the support I 4 and the support II 5 respectively. In the embodiment, the sizes of the aluminum profile and the wooden swing arm 9 are designed to ensure that the impact head 6 is in contact with the agricultural material when the wooden swing arm 9 is in a vertical position (i.e. perpendicular to the base plate 1).

[0035] The digital signal processing experiment box 11 is installed on top of the support I 4 and the support II 5, is connected to a computer, receives signals collected by the force sensor 7 and the angle encoder 10, and controls on-off of the electromagnetic switch 20.

[0036] A method for using an agricultural material collision mechanics property determination test bench is as follows:

[0037] At the initial state, the control electromagnetic switch 20 is powered, the iron sheet 21 is released, the wooden swing arm 9 is perpendicular to the bottom plate 1, at this time, the electric signal collected by the angle encoder 10 is processed through the signal processing circuit, and the reading displayed at the computer end is 0; the agricultural material to be tested is placed on the material base 13, the impact head 6 is in contact with the agricultural material, the wooden swing arm 9 is artificially lifted until the angle between the wooden swing arm 9 and the vertical direction is displayed as θ at the computer end, the nuts at the two ends of the connecting rod and the angle adjusting disc I 18 and the angle adjusting disc II 19 are adjusted, the iron sheet 21 can be firmly attracted by the electromagnetic switch 20 when the electromagnetic switch 20 is powered off, the control electromagnetic switch 20 is powered on, then powered on, the wooden swing arm 9 freely falls, at the moment when the impact head 6 hits the agricultural material to be tested on the material base 13, the pressure borne by the force sensor 7 is the collision force generated in this collision, and the electric signal obtained by the angle encoder 10 is processed through the signal processing circuit, and the deformation (including the deformation amount and the deformation rate, the calculation process is the prior art) of the agricultural material to be tested generated at the moment after the collision is calculated at the computer end; the above process is repeated, the angle between the wooden swing arm 9 and the vertical direction is changed, and finally the relationship between the deformation and the pressure generated by the collision of the agricultural material under different working conditions is obtained.

[0038] The agricultural material of the present application includes but is not limited to rice stems, wheat stems, apples, potatoes and citrus fruits. For the stem agricultural material, the shape of the impact head 6 is T-shaped, and the shape of the end of the material base 13 is similar to V-shaped. For the apple, potato and citrus agricultural material, the shape of the impact head 6 is spherical, and the material base 13 is L-shaped. The agricultural material is placed on the material base 13 and fixed by a rubber band or the like. The modeling process is described below by taking the collision of the potato as an example.

[0039] The obtained collision force and deformation are used for collision modeling, and the specific steps are as follows:

[0040] (1) Analyze the characteristics of the collision force and deformation to determine the contact mechanics model

[0041] In the dynamic loading process of a certain working condition collision, the surface of the potato starts to be elastically deformed, and is still in the elastic region. When the collision force reaches the yield point of the potato, it enters the plastic loading stage, and the collision force applied to the potato decreases in an elastic trend and increases in a plastic trend. With the change of time, part of the energy is lost, leading to irreversible deformation of the potato. Finally, in the unloading stage, the collision force is mainly in a plastic deformation trend, accompanied by energy loss and reduction of impact speed. The plastic loading stage is described by using the K-K model:

[0042]

[0043] The unloading stage is described by using the Y-K model:

[0044]

[0045] Where: E* is the equivalent elastic modulus of the two colliding bodies (i.e., the impact head and the agricultural material), R * It is the equivalent radius of curvature of the two colliding bodies, and δ represents the deformation of the two contacting colliding bodies. A represents the deformation rate of two colliding bodies. * K represents the equivalent dissipation constant. h It is Hertzian stiffness, K y It is the linear stiffness during the elastic loading stage, δ y δ represents the yield point of agricultural materials. m K represents the maximum deformation of the two colliding bodies. y and K h The relationship between them is:

[0046]

[0047] Combining the KK model and the YK model, the former describes the elastic deformation of the potato in the initial stage of the collision and can well describe the viscoelastic properties of the collision force, while the latter can well describe the plastic state of the potato after elastic deformation; superimposing the equivalent dissipation term of the KK model onto the YK model, a new model (i.e., the contact mechanics model) is obtained, which can be described as follows:

[0048]

[0049] (2) Obtain the equivalent elastic modulus of the potato

[0050] An experiment was conducted on the compressive mechanical properties of potatoes, and the results were based on the compression test data ( Figure 3 Based on Hertz's elastic sphere contact theory (Equation (5)), the equivalent elastic modulus E1 of the potato was fitted. * ( Figure 4 ):

[0051]

[0052] Where: F1 is the pressure measured during the compression mechanical properties experiment, and R1 * The equivalent radius of curvature of the potato and the compression disc of the texture analyzer is represented by δ1, and the deformation measured during the compression mechanical property test is represented by δ1. The equivalent elastic modulus E1 of the potato is fitted. * The equivalent elastic modulus E* in the KK model, YK model, and new model.

[0053] (3) Data fitting and model building

[0054] The contact force model (formula (4)) is fitted with the measured data of the test bench to obtain the parameters A*, K h and K y in formula (4), see Table 1, and the above parameter values are substituted into the K-K model, Y-K model and the new model (formula (1), (2), (4)) to draw the force variation curves of the three models, which are compared with the actual force variation curve measured by the test bench of the application (see Fig. 2) Figure 5 ), and the force variation curve of the new model is closer to the measured value. The parameters R * and δ y involved in the model are directly measured, and δ and are measured by the angle encoder in the test bench of the application.

[0055] Table 1 Model parameters

[0056]

[0057] (4) Model effect analysis

[0058] The new model considers the parameters of the yield point of the potato and increases the equivalent dissipation term, and can accurately describe the energy dissipation of the potato due to deformation in the whole plastic loading stage and unloading stage. It can be seen from Figure 6 that the fitting degree of the force variation curve of the new model and the measured curve is high, the average R value reaches about 0.85, which is similar to the measured data, and the R value of the K-K model and the Y-K model is only about 0.45.

[0059] The embodiments are preferred embodiments of the application, but the application is not limited to the above embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art without departing from the essential content of the application shall fall within the protection scope of the application.

Claims

1. A method for establishing a collision model for an experimental platform for determining the collision mechanical properties of agricultural materials, characterized in that, include: A wooden swing arm (9) is fixed at one end to a shaft (16) and a force sensor (7) is installed at the other end; an impact head (6) is installed on the force sensor (7); one end of the shaft (16) passes through a bearing seat (17) and the other end is connected to an angle encoder (10), and both the bearing seat (17) and the angle encoder (10) are fixed. The material base (13) is on which agricultural materials are placed, and when the wooden swing arm (9) is in a vertical position, the impact head (6) is in contact with the agricultural materials. The wooden swing arm (9) is connected to an iron plate (21) in the middle. The iron plate (21) is attracted by an electromagnetic switch (20) that is not powered. The electromagnetic switch (20) is adjustablely mounted on the connector (22) via a connecting rod. Angle adjustment discs are fixed at both ends of the connector (22). The force sensor (7), angle encoder (10) and electromagnetic switch (20) all communicate with the digital signal processing experimental box (11), which is connected to a computer. When the agricultural material is potatoes, the collision model is as follows: ,in: It is the equivalent elastic modulus of the two colliding bodies. It is the equivalent radius of curvature of the two colliding bodies. This represents the amount of deformation of the two colliding bodies. This represents the deformation rate of the two colliding bodies. Represents the equivalent dissipation constant. It is Hertzian stiffness. It is the linear stiffness during the elastic loading stage. Indicates the yield point of agricultural materials. This represents the maximum deformation of the two colliding bodies. It is the collision force.

2. The method for establishing a collision model for the test bench for measuring the collision mechanical properties of agricultural materials according to claim 1, characterized in that, The material base (13) is fixed to the aluminum profile. (3) One end, aluminum profile (3) The other end is connected to the aluminum profile (2) Vertically fixed, aluminum profile (2) Fix it on the base plate (1).

3. The method for establishing a collision model for the test bench for measuring the collision mechanical properties of agricultural materials according to claim 2, characterized in that, The aluminum profile (3) The middle position is fixed to the base plate (1) by a square base (23).

4. The method for establishing a collision model for the test bench for determining the collision mechanical properties of agricultural materials according to claim 2, characterized in that, Symmetrical fixed brackets on the base plate (1) (4) and support (5) The bracket (4) and support (5) An upper fixed rectangular bracket (12) is provided, on which a bearing seat (17) and an angle encoder (10) are fixed.

5. The method for establishing a collision model for the test bench for measuring the collision mechanical properties of agricultural materials according to claim 4, characterized in that, The angle adjustment dial is fixed to the bracket. (4) and support (5) Above.

6. The method for establishing a collision model for the test bench for measuring the collision mechanical properties of agricultural materials according to claim 1, characterized in that, The agricultural materials include, but are not limited to, rice stalks, wheat stalks, apples, potatoes, and citrus fruits.

7. The method for establishing a collision model for the test bench for determining the collision mechanical properties of agricultural materials according to claim 6, characterized in that, For agricultural materials such as stalks, the impact head (6) is T-shaped, and the end of the material base (13) is V-shaped.

8. The method for establishing a collision model for the test bench for determining the collision mechanical properties of agricultural materials according to claim 6, characterized in that, For agricultural materials such as apples, potatoes, and citrus, the impact head (6) is spherical and the material base (13) is L-shaped.

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