Finite element parametric modeling method for manned lunar rover metal screen wheel

Abstract

This invention provides a finite element parametric modeling method for a manned lunar rover's metal mesh wheel, comprising the following steps: Step S1, providing model parameters for the woven wheel; Step S2, obtaining the curve parametric equations describing the position and shape of each metal wire; Step S3, calculating the intersection points between every two metal wires, and determining the position coordinates of the metal wires in contact state based on their spatial position and diameter; Step S4, calculating the node information and element information of the finite element model; Step S5, generating a text-formatted finite element model file; Step S6, importing the model into finite element calculation software, setting loads and boundary conditions, and performing calculations. This invention directly generates a finite element mesh based on the geometric characteristics of the metal wires, greatly shortening the modeling time; it achieves parametric finite element modeling, enabling the generation of new finite element models based on information such as weaving angle, number of metal wires, mesh size, and wheel cross-section, which is highly beneficial for rapid iteration in the wheel design stage.

Description

Technical Field

[0001] This invention relates to the field of manned lunar rover design and manufacturing, and in particular to a finite element parametric modeling method for a manned lunar rover's metal screen wheel. Background Technology

[0002] As a key component of manned lunar rovers, wheels serve as the physical interface between the vehicle system and the lunar environment, decisively influencing the rover's traction, braking performance, and ride comfort. Due to the complexity of the lunar environment and the weight constraints of the launch mission, metal woven mesh wheels are the preferred option for manned lunar rover wheels.

[0003] Using the finite element method (FEM) for static and dynamic analyses of products is a common practice in aerospace product design and manufacturing, effectively shortening the development cycle and reducing costs. Furthermore, the manufacturing process of metal woven elastic screen wheels is complex, time-consuming, and costly; therefore, simulation verification based on the finite element method is particularly important. However, finite element modeling of metal screen wheels presents several challenges:

[0004] 1. Metal screen wheels are woven from hundreds or even thousands of metal wires. The spatial position of each wire is affected by various factors such as the wheel cross-section, weaving angle, wire diameter, and number of wires. Therefore, determining the spatial position of each wire quickly and accurately is the first challenge in finite element modeling.

[0005] 2. The metal wires are in contact with each other. Depending on the number of wires, the metal screen surface contains thousands or even tens of thousands of contact pairs. Furthermore, the slenderness ratio of the wires is much greater than 10. Considering computational accuracy and efficiency, only one-dimensional beam or rod elements can be used for modeling. This results in line-to-line contact between the wires, while finite element analysis software is generally better suited to handling surface-to-surface contact. Therefore, accurately establishing contact among thousands or even tens of thousands of contact pairs is the second challenge in finite element modeling.

[0006] 3. During the development phase of the manned lunar rover, it is necessary to rapidly iterate on the wheel configuration and analyze the impact of different design parameters on wheel performance. Therefore, how to quickly establish a finite element model based on design parameters such as wheel cross-section, wire diameter and quantity, and intersection angle is the third challenge in modeling.

[0007] In summary, how to quickly and accurately establish a finite element model of a metal screen wheel has become a key technology restricting the design and simulation of manned lunar rover wheels, and a parametric modeling method is urgently needed. Summary of the Invention

[0008] The purpose of this invention is to provide a finite element parametric modeling method for metal mesh wheels of manned lunar rovers, so as to solve the problems of difficult modeling of woven tires, time-consuming and labor-intensive modeling, and poor model reusability in the existing technology.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is: to provide a finite element parametric modeling method for a manned lunar rover's metal screen wheel, comprising the following steps:

[0010] Step S1: Given the model parameters of the braided wheel, including braiding angle, wheel cross-sectional shape, number of wires, unit size, material density and Young's modulus;

[0011] Step S2: Based on the shape of the wheel cross section, without considering the weaving and crossing of the metal wires, obtain the curve parametric equations describing the position and shape of each metal wire.

[0012] Step S3: Calculate the intersection point between every two metal wires based on the curve parameter equation obtained in step S2, and determine the position coordinates of the metal wires in the contact state based on the spatial position and diameter of the metal wires.

[0013] Step S4: Based on the wire position coordinates obtained in step S3, and combined with the given element size, calculate the node information and element information of the finite element model, including node number, node coordinates, element number, and element cross-sectional direction.

[0014] Step S5: Using the node information and element information obtained in step S4, generate a finite element model file in text format;

[0015] Step S6: Import the finite element calculation software, set the loads and boundary conditions, and perform the calculation.

[0016] Furthermore, step S5 specifically includes:

[0017] Using the node and cell information obtained in step S4, an inp file is generated according to the inp file syntax rules of the Abaqus software.

[0018] Furthermore, step S6 specifically includes:

[0019] The finite element model of the braided tire was obtained by reading the inp file using Abaqus software. A general contact was set up, and the edge-to-edge formulation assignment was enabled in Contact Formulation to take the wire radius into account in the contact detection. Then, loads and boundary conditions were set according to the analysis requirements, and static and dynamic analyses were carried out.

[0020] Furthermore, step S2 includes:

[0021] Step S2-1: Assuming the wheel's rotation axis is the y-axis, the cross-section lies in the yoz plane. Discretize the cross-section curve into a series of scattered points and output the coordinates of each point. ;

[0022] Step S2-2: Use the least squares method to fit the cross-sectional curve to parameters. The function, i.e. The minimum value of the parameter is The maximum value is Furthermore, by rotating the fitted curve around the y-axis, the spatial equation of the wheel surface is obtained. ;

[0023] Step S2-3, the braiding angle of the metal wire is The rotation angles of the two intersecting metal wires around the z-axis are respectively Its spatial equation is the relationship between the wheel surface and... The lines of intersection in the plane; the spatial equations of the two intersecting metal wires are as follows:

[0024] ;

[0025] Step S2-4: If the circumferential array of metal wires is N, then the angle between any two metal wires is... The i-th metal wire rotates relative to the 1st metal wire along the y-axis. Using the rotation matrix, the spatial coordinates of the i-th metal wire are obtained. and .

[0026] Furthermore, step S3 includes:

[0027] Step S3-1: For the m-th forward-braided wire and the nth negatively braided metal wire Constructor function ;

[0028] Step S3-2: Calculate the function using the Levenberg-Marquardt algorithm. Zero point The zero point is the intersection of the m-th and n-th metal wires. ,in These are the parameters corresponding to the intersection point on wire m. This is the parameter corresponding to wire n;

[0029] Step S3-3: The two braided metal wires intersect at the point... The points are not common nodes. Based on the spatial equations of the two wires, the values ​​at the intersection points are calculated separately. The tangent vectors T1 and T2 at the point are then cross-producted using T1 and T2 to obtain... Vector T3 is perpendicular to the plane formed by the two intersecting metal wires, thus determining the intersection point of the two braided metal wires. The bias direction, the bias distance is the radius of the metal wire;

[0030] Step S3-4: Repeat steps S3-1 to S3-3 to calculate the parameters of the intersection points between all the metal wires. And the coordinates of the intersection points after offset, thus obtaining the spatial coordinates of each metal wire after weaving.

[0031] Furthermore, and They are not necessarily equal.

[0032] The beneficial effects of the finite element parametric modeling method for the metal screen wheel of the manned lunar rover provided by this invention are:

[0033] This invention proposes a parametric finite element modeling method for woven metal wire tires on lunar rovers, effectively solving problems such as difficulty in modeling woven tires, time-consuming and labor-intensive processes, and poor model reusability. Typically, finite element modeling follows a process of first establishing the geometric model and then meshing. When dealing with woven metal wire tires, it is necessary to first draw the curves of each metal wire in CAD software, then import the model into finite element preprocessing software, where operations such as geometry cleanup, element division, and specifying element cross-sectional directions are performed. After completion, the model is imported into finite element calculation software for computation. Due to the large number of metal wires in the model, performing these operations is extremely time-consuming and labor-intensive. Furthermore, the model has poor reusability; once parameters such as the weaving angle and the number of metal wires are changed, the finite element model needs to be rebuilt, which is detrimental to the design iteration of the wheel.

[0034] Compared with existing technologies, the modeling method proposed in this invention adopts a bottom-up modeling approach, directly generating finite element meshes based on the geometric characteristics of the metal wires, which greatly shortens the modeling time; it realizes the parameterization of finite element modeling, and can generate new finite element models based on information such as weaving angle, number of metal wires, mesh size, and wheel cross-section, which is very beneficial for rapid iteration in the wheel design stage. Attached Figure Description

[0035] The invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 This is a basic flowchart of the finite element parametric modeling method for woven screen wheels provided in an embodiment of the present invention;

[0037] Figure 2This is a CAD model drawing of a screen wheel provided in an embodiment of the present invention;

[0038] Figure 3 A cross-sectional shape diagram of a woven wheel provided in an embodiment of the present invention;

[0039] Figure 4a , 4b A curve fitting effect diagram based on the least squares method provided for an embodiment of the present invention;

[0040] Figure 5 A finite element model diagram of a woven screen wheel considering contact, provided for an embodiment of the present invention;

[0041] Figure 6 A diagram showing the relationship between radial deformation of a wheel and wheel center load, provided for an embodiment of the present invention. Detailed Implementation

[0042] The finite element parametric modeling method for the metal screen wheel of the manned lunar rover proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0043] The core idea of ​​this invention is to propose a parametric finite element modeling method for woven metal wire tires on lunar rovers, effectively solving the problems of difficult, time-consuming, labor-intensive, and poor model reusability in woven tire modeling. Typically, finite element modeling follows a process of first establishing the geometric model and then meshing. When dealing with woven metal wire tires, it is necessary to first draw the curves of each metal wire in CAD software, then import the model into finite element preprocessing software, where operations such as geometry cleaning, element division, and specifying element cross-sectional directions are performed. After completion, the model is imported into finite element calculation software for calculation. Due to the large number of metal wires in the model, performing these operations is extremely time-consuming and labor-intensive. Furthermore, the model has poor reusability; once parameters such as the weaving angle and the number of metal wires are changed, the finite element model needs to be rebuilt, which is detrimental to the design iteration of the wheel.

[0044] Compared with existing technologies, the modeling method proposed in this invention adopts a bottom-up modeling approach, directly generating finite element meshes based on the geometric characteristics of the metal wires, which greatly shortens the modeling time; it realizes the parameterization of finite element modeling, and can generate new finite element models based on information such as weaving angle, number of metal wires, mesh size, and wheel cross-section, which is very beneficial for rapid iteration in the wheel design stage.

[0045] like Figure 1As shown, this embodiment relates to a finite element parametric modeling method for a lunar rover's braided metal wire tire, including the following steps:

[0046] Step 1: Given the model parameters of the wheel, including weaving angle, geometry, number of wires, number of units, material density and Young's modulus, as shown in Table 1.

[0047] Table 1 Wheel Model Parameters

[0048] parameter numerical values Geometric shapes like Figure 1 Weaving angle 45° Number of metal wires 800 wire diameter 0.83 mm Number of units Each metal wire has no fewer than 100 Material steel

[0049] Step 2: Based on the shape of the wheel's cross-section, such as... Figure 2 As shown, without considering wire weaving and crossing, the parametric equations describing the position and shape of each wire are obtained, specifically including:

[0050] Step 2.1: Assuming the wheel's rotation axis is the y-axis, the cross-section lies in the yoz plane. Discretize the cross-section curve into a series of scattered points and output the coordinates of each point. To ensure the discretization accuracy of the cross-sectional curve, it is recommended that the number of discrete points be no less than 200. In this embodiment, the number of discrete points is 515.

[0051] Step 2.2: Use the least squares method to fit the cross-sectional curve to parameters. The function, i.e. The minimum value of the parameter is The maximum value is Furthermore, by rotating the fitted curve around the y-axis, the spatial equation of the wheel surface can be obtained. .

[0052] Minimum value of parameters and maximum value There are no particular restrictions, only consistency must be ensured. In this embodiment, , This is equal to the number of discrete points used. When fitting using the least squares method, in order to ensure that the fitting function has good adaptability to various curves, a 7th order Fourier series is selected as the fitting function, and the fitting effect is shown in Figure 4.

[0053] Step 2.3, the braiding angle of the metal wire is The rotation angles of the two intersecting metal wires around the z-axis are respectively Its spatial equation is the relationship between the wheel surface and... The lines of intersection in the plane. It's not difficult to derive the spatial equations of the two intersecting metal wires as follows:

[0054]

[0055] In this embodiment, °.

[0056] Step 2.4: If the circumferential array of metal wires consists of 400 wires, then the included angle between every two metal wires is... It is 0.9°, the i-th wire has rotated relative to the 1st wire along the y-axis. 0.9°. Using the rotation matrix, the spatial coordinates of the i-th wire can be obtained. and .

[0057] After step 2, the spatial curve of each metal wire can be determined based on the design parameters without considering the cross contact of the metal wires.

[0058] Step 3: Based on the spatial curve of the metal wires obtained in the previous step, calculate the intersection point between every two metal wires, and determine the position coordinates of the metal wires in the contact state according to their spatial position and diameter. The specific steps are as follows:

[0059] Step 3.1: For the m-th forward-braided wire and the nth negatively braided metal wire Constructor function .

[0060] Step 3.2: Calculate the function using the Levenberg-Marquardt algorithm. Zero point The zero point is the intersection of the m-th and n-th metal wires. ,in These are the parameters corresponding to the intersection point on wire m. This refers to the parameter corresponding to wire n. It's important to note that... and They are not necessarily equal.

[0061] Step 3.3: The two braided metal wires intersect at the point... The points are not common nodes. Based on the spatial equations of the two wires, the values ​​at the intersection points are calculated separately. The tangent vectors T1 and T2 at the point are then cross-producted using T1 and T2 to obtain... Vector T3 is perpendicular to the plane formed by the two intersecting metal wires, thus determining the intersection point of the two braided metal wires. The bias direction is such that the bias distance is the radius of the metal wire, which is 0.415 mm in this embodiment.

[0062] Step 3.4: Repeat steps 3.1 to 3.3 to calculate the parameters of all intersection points between the metal wires. And the coordinates of the intersection points after offset, thus obtaining the spatial coordinates of each metal wire after weaving.

[0063] Step 4: Based on the spatial coordinates of the metal wire obtained in Step 3, and combined with the given element size, calculate the node information and element information of the finite element model, including node number, node coordinates, element number, and element cross-sectional direction.

[0064] Step 5: Using the node and cell information obtained in the above steps, generate an inp file according to the inp file syntax rules of the Abaqus software.

[0065] Step 6: Use Abaqus software to read the .inp file to obtain the finite element model of the braided tire, such as... Figure 5 As shown. Set up general contact and enable "Edge-to-edge formulation assignment" in "Contact Formulation" to consider the wire radius in contact detection. Then, set loads and boundary conditions according to the analysis requirements, calculate the radial stiffness of the woven wheel, and the relationship between its radial deformation and the wheel center load is shown in the figure. Figure 6 As shown, the calculation results agree well with the experimental results, indicating that the model has high calculation accuracy.

[0066] The contents not described in detail in this specification are prior art known to those skilled in the art. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A finite element parametric modeling method for metal screen wheels of manned lunar rovers, characterized in that, Includes the following steps: Step S1: Given the model parameters of the braided wheel, including braiding angle, wheel cross-sectional shape, number of wires, unit size, material density and Young's modulus; Step S2: Based on the shape of the wheel cross section, without considering the weaving and crossing of the metal wires, obtain the curve parametric equations describing the position and shape of each metal wire. Step S3: Calculate the intersection point between every two metal wires based on the curve parameter equation obtained in step S2, and determine the position coordinates of the metal wires in the contact state based on the spatial position and diameter of the metal wires. Step S4: Based on the wire position coordinates obtained in step S3, and combined with the given element size, calculate the node information and element information of the finite element model, including node number, node coordinates, element number, and element cross-sectional direction. Step S5: Using the node information and element information obtained in step S4, generate a finite element model file in text format; Step S6: Import the finite element method software, set the loads and boundary conditions, and perform the calculation; Step S2 includes: Step S2-1: Assuming the wheel's rotation axis is the y-axis, the cross-section lies in the yoz plane. Discretize the cross-section curve into a series of scattered points and output the coordinates of each point. ; Step S2-2: Use the least squares method to fit the cross-sectional curve to parameters. The function, i.e. The minimum value of the parameter is The maximum value is Furthermore, by rotating the fitted curve around the y-axis, the spatial equation of the wheel surface is obtained. ; Step S2-3, the braiding angle of the metal wire is The rotation angles of the two intersecting metal wires around the z-axis are respectively Its spatial equation is the relationship between the wheel surface and... The lines of intersection in the plane; the spatial equations of the two intersecting metal wires are as follows: ； Step S2-4: If the circumferential array of metal wires is N, then the angle between any two metal wires is... The i-th metal wire rotates relative to the 1st metal wire along the y-axis. Using the rotation matrix, the spatial coordinates of the i-th metal wire are obtained. and ; Step S3 includes: Step S3-1: For the m-th forward-braided wire and the nth negatively braided metal wire Constructor function ; Step S3-2: Calculate the function using the Levenberg-Marquardt algorithm. Zero point The zero point is the intersection of the m-th and n-th metal wires. ,in These are the parameters corresponding to the intersection point on wire m. This is the parameter corresponding to wire n; Step S3-3: The two braided metal wires intersect at the point... The points are not common nodes. Based on the spatial equations of the two wires, the values ​​at the intersection points are calculated separately. The tangent vectors T1 and T2 at the point are then cross-producted using T1 and T2 to obtain... Vector T3 is perpendicular to the plane formed by the two intersecting metal wires, thus determining the intersection point of the two braided metal wires. The bias direction, the bias distance is the radius of the metal wire; Step S3-4: Repeat steps S3-1 to S3-3 to calculate the parameters of the intersection points between all the metal wires. And the coordinates of the intersection points after offset, thus obtaining the spatial coordinates of each metal wire after weaving; and They are not necessarily equal.

2. The finite element parametric modeling method for the metal screen wheel of a manned lunar rover according to claim 1, characterized in that, Step S5 specifically involves: Using the node and cell information obtained in step S4, an inp file is generated according to the inp file syntax rules of the Abaqus software.

3. The finite element parametric modeling method for the metal screen wheel of a manned lunar rover according to claim 2, characterized in that, Step S6 specifically involves: The finite element model of the braided tire was obtained by reading the inp file using Abaqus software. A general contact was set up, and the edge-to-edge formulation assignment was enabled in Contact Formulation to take the wire radius into account in the contact detection. Then, loads and boundary conditions were set according to the analysis requirements, and static and dynamic analyses were carried out.

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