Parametric modeling method for guide mechanism of Mars ascender

Abstract

The invention discloses a parametric modeling method for a guide mechanism of a Mars ascender, and belongs to the field of parametric modeling of guide mechanism structures. According to the method, the Python language is used for carrying out secondary development on the finite element Abaqus, parametric modeling of the ascender thermal emission guiding mechanism is achieved, and the finite element modeling efficiency is improved. Through parameterized establishment and assembly of slide block components, parameterized setting of contact and connection relationships and parameterized setting of loads, rapid modeling of finite element models of guide mechanisms with different slide block sizes, slide block installation numbers and installation positions is realized; and the problem that the reliability of a test result is reduced due to different gravity environments of the ground and the fire surface can be avoided. The established Mars ascender guide mechanism model is submitted to Abaqus for finite element analysis, and the optimal design parameters of the guide mechanism are obtained by analyzing the relation between the pitch angle speed and the design parameters when the ascender leaves the guide rail. According to the method, the precision and efficiency of parametric modeling of the guide mechanism of the Mars ascender can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural parameterized modeling, and in particular relates to a parameterized modeling method for a Mars ascender guide mechanism. Background Art

[0002] Mars is the planet most similar to the Earth in the solar system. The Mars sampling and return mission has very important significance and scientific value. After obtaining the fire soil sample, the Mars ascender is launched on the surface of Mars and takes off. This is the key link of the Mars sampling and return mission. Therefore, it is necessary to study the Mars surface launch technology of the Mars ascender to ensure the smooth implementation of the return mission. The thermal launch process is simple, the technology is very mature, and the launch reliability is high. The thermal launch device is mainly composed of a bracket, a vertical cylinder, and a clamping device. Among them, the guide rail set in the bracket cooperates with the slider installed on the ascender as a guide mechanism during launch to prevent the ascender from uncontrolled rolling motion, so that the movement of the ascender before ignition and launch is constrained and guided by the orbit, so that it has good initial orientation performance. However, the size of the slider, the number of sliders installed, and the installation position will affect the pitch angular velocity of the ascender after leaving the guide rail after the guide rail-slider guidance. Too large a pitch angular velocity will bring difficulties to the GNC flight control strategy after the ascender leaves the guide rail, which will lead to the failure of the sampling and return mission. Therefore, it is necessary to reasonably design parameters such as the slider size, the number of sliders installed and the installation position to obtain the best guiding effect, that is, a smaller pitch angular velocity.

[0003] In order to be able to deeply study the influence of different slider sizes, the number of sliders installed and the installation position on the pitch angular velocity of the ascender after the guide rail-slider guidance, it is often necessary to have a large number of guide mechanism design methods and their corresponding pitch angular velocity data of the ascender when it is launched for analysis. The existing research technologies are: 1) Conducting physical tests by designing different guide rail-slider mechanisms, obtaining test data by installing angular velocity sensors on the ascender, and comparing the launch pitch angular velocity of the ascender in the test data to obtain appropriate guidance parameters. 2) Using traditional modeling methods, different slider models are established according to different slider sizes required for research, different assembly operations are performed according to different slider installation numbers and installation positions, and contact relationships are set according to different slider guide rail contact conditions, and then a finite element model is established. The problems and defects of the existing technology are: 1) The cost of using experiments to study the design scheme of the guide rail-slider is too high. 2) The different gravity environments on the ground and the fire surface lead to a decrease in the reliability of the test results. 3) The assembly process and contact relationship setting of multiple sliders need to be manually operated step by step, resulting in cumbersome and time-consuming operation steps in the modeling process. 4) When the guiding parameters such as the slider size, the number of sliders installed and the installation position change, the conventional modeling method requires all the modeling steps to be repeated, resulting in an extremely low degree of automation in the modeling process, which seriously wastes the researchers' time and energy. Summary of the invention

[0004] In order to solve the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a parametric modeling method for a guide rail slider guide mechanism of a Mars ascender, and to realize the parametric modeling of the guide rail slider guide mechanism of the ascender thermal launch by secondary development of the finite element software Abaqus; by parameterizing the establishment of slider components, parameterizing the assembly of slider components, parameterizing the setting of contact relationships and connection relationships, and parameterizing the setting of loads, the rapid modeling of the finite element model of the guide mechanism with different slider sizes, the number of sliders installed, and the installation position can be realized, which can avoid the problem of reduced reliability of test results due to the different gravity environments of the ground and the Mars surface, and can significantly reduce the probability of modeling errors. On this basis, the Mars ascender guide mechanism model established by the present invention is submitted to the finite element software Abaqus for finite element analysis, and the optimal design parameters of the guide rail-slider can be obtained by analyzing the relationship between the pitch angular velocity when the ascender leaves the guide rail and the design parameters.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] The present invention discloses a parametric modeling method for a Mars ascender guidance mechanism, comprising the following steps:

[0007] Step 1: Create and import the riser, bracket and rail components;

[0008] 1.1. Create component models; the components include fairing, payload compartment, second-stage tank, second-stage solid rocket engine, interstage, first-stage tank, and first-stage solid rocket engine;

[0009] 1.2. Assemble the component models created in 1.1 to obtain the ascender components and save them in sat format;

[0010] 1.3. Use the Part From Geometry File function to import the ascender parts in 1.2;

[0011] 1.4. Create the models of the bracket and guide rail components respectively and save them in sat format;

[0012] 1.5. Use the Part From Geometry File function to import the bracket and guide rail parts of 1.4;

[0013] Step 2: Determine the slider parameter variables required for modeling and create the slider component parametrically;

[0014] 2.1. The slider parameter variables include: slider length L, slider total height H, slider lower side height H1, slider slope angle α, slider bottom width D1 and top width D2;

[0015] 2.2. Set the current window sketching state through the set Primary Object function;

[0016] 2.3. Use the Line function to input the coordinates (0,0), (D1,0), (D1,H), (D1-D2,H), (D1-D2,H1+(D1-D2)×sinα), (0,H1), (0,0) in sequence to complete the plane sketch of the slider section and obtain the plane sketch;

[0017] 2.4. Use the Base Solid Extrude function to stretch the plane sketch in 2.3 into a slider component with a length of L;

[0018] Step 3: Assemble the bracket, rails and riser;

[0019] 3.1. Add the bracket components and guide rail components in 1.5 to the assembly interface through the Instance function;

[0020] 3.2. Use the translate function to move the guide rail to the position where the guide rail is installed in the bracket to achieve the assembly of the two;

[0021] 3.3. Use the Radial Instance Pattern function to move the other rail symmetrically to the corresponding position of the bracket;

[0022] 3.4. Add the ascender component in 1.3 to the assembly interface through the Instance function;

[0023] 3.5. Assemble the ascender component and the bracket component through the translate function;

[0024] Step 4: Determine the parameter variables required for the slider assembly and parameterize the assembly slider;

[0025] 4.1. The parameter variables required for assembly include: the number of slider groups N, the installation position of the slider, that is, the position of each slider from the left end of the guide rail l1, l2, ..., l N ;

[0026] 4.2. Continue to add N slider components to the assembly interface through the Instance function;

[0027] 4.3. Use the translate function to move the N slider components to the positions l1, l2, …, l away from the left end of the guide rail. N location;

[0028] 4.4. Use the Radial Instance Pattern function to symmetrically assemble the N sliders to the corresponding positions of the guide rail on the other side to complete the parametric assembly of the sliders; obtain the assembly of the Mars ascender guide mechanism;

[0029] Step 5: Set a collection for each component in the assembly and set rigid body constraints; the components are the riser, bracket, guide rail and slider;

[0030] 5.1. Use the Reference Point function to set reference points at the center of gravity of the ascender and slider and the center of rotation of the bracket;

[0031] 5.2. Use the local function to set the reference point in 5.1 to the corresponding reference point set;

[0032] 5.3. Use the get By Bounding Sphere function to define the ascender, bracket, two guide rails and 2N slider components as sets with the same name;

[0033] 5.4. Use the Rigid Body function to select the center of gravity of the ascender and the ascender set to set the ascender as a rigid body; select the rotation center of the bracket and the bracket set to set the bracket as a rigid body; select the rotation center of the bracket and the guide rail set to set the two guide rails as rigid bodies;

[0034] 5.5. Use the range function to traverse the 2N sliders, and use the Rigid Body function to select the center of gravity of the current slider and the slider set to set the 2N sliders as rigid bodies in turn;

[0035] Step 6: Parameterize and determine the contact surfaces and connection surfaces of each component; the contact surfaces are the surfaces of each component that need to be set up for face-to-face contact; the connection surfaces are the surfaces that need to be set up for binding constraints;

[0036] 6.1. Use the range function to traverse the N sliders on the left side of the ascender, use the find At function to select the top surface of each slider bound to the ascender, and use the Surface function to define the top surface as the connection surface surf-tie-xL. Similarly, use the find At function to select the four side surfaces and one bottom surface of the slider in contact with the guide rail, and use the Surface function to define them as contact surfaces surf-1-xL, surf-2-xL, surf-3-xL, surf-4-xL and surf-5-xL, where x ranges from 0 to N. Similarly, use the range function to define the connection surfaces of the N sliders on the right side of the ascender as surf-tie-xR, and the contact surfaces as surf-1-xR, surf-2-xR, surf-3-xR, surf-4-xR and surf-5-xR, where x ranges from 0 to N.

[0037] 6.2. Use find At and Surface functions to set the outer surface of the ascender as the connection surface between the slider and the ascender, surf-tie-MAV;

[0038] 6.3. Use find At and Surface functions to define the surfaces in contact with the slider in the guide rail component. The four side surfaces and bottom surfaces of the left guide rail of the ascender in contact with the slider are defined as contact surfaces surf-daogui-1-L, surf-daogui-2-L, surf-daogui-3-L, surf-daogui-4-L, and surf-daogui-5-L, respectively. The four side surfaces and bottom surfaces of the other guide rail in contact with the slider are defined as contact surfaces surf-daogui-1-R, surf-daogui-2-R, surf-daogui-3-R, surf-daogui-4-R, and surf-daogui-5-R, respectively.

[0039] 6.4. Use find At and Surface functions to define the connection surfaces surf-tie-daogui-L and surf-tie-daogui-R in the guide rail component that are bound to the bracket, and the connection surfaces surf-tie-tuojia-L and surf-tie-tuojia-R in the bracket component that are bound to the guide rail;

[0040] Step 7: Parameterize the contact surface and connection surface parameterized in step 6, and set the contact relationship and connection relationship;

[0041] 7.1. For the contact situation of the guide rail and slider on the left side of the ascender, use the range function to traverse the five contact surfaces, and use the range function to traverse the N sliders for each contact surface. Use the Surface ToSurface Contact Exp function to establish a surface-to-surface contact relationship between the five contact surfaces of each slider and the corresponding contact surface of the guide rail, that is, set the contact surfaces surf-ixL and surf-daogui-iL as surface-to-surface contact pairs, where i is 1 to 5 and x is 1 to N; set the contact relationship between the guide rail and slider on the right side of the ascender in the same way;

[0042] 7.2. Use the tie function to establish binding constraints between the guide rail and the bracket, that is, set the connecting surfaces surf-tie-daogui-L and surf-tie-tuojia-L as binding constraints, and set the connecting surfaces surf-tie-daogui-R and surf-tie-tuojia-R as binding constraints;

[0043] 7.3. Use the tie function to establish binding constraints between the ascender and the 2N sliders; that is, use the range function to traverse the N sliders, set the left connecting surfaces surf-tie-xL and surf-tie-MAV as binding constraints, and similarly set the right connecting surfaces surf-tie-xR and surf-tie-MAV as binding constraints, where the value of x is 1 to N;

[0044] Step 8: In order to solve the problem that the different gravity environments on the ground and on Mars may lead to reduced reliability of the results, gravity loads are parametrically applied, thrust loads and boundary conditions are set, and parametric modeling is completed to obtain the Mars ascender guidance mechanism model;

[0045] 8.1. Apply gravity load to the ascender. The key parameter of gravity load is the vertical angle β.

[0046] 8.2. Use Tabular Amplitude function to define the gravity amplitude change curve Amp-G and thrust amplitude change curve Amp-F;

[0047] 8.3. Use the Gravity function to define gravity for the assembly. The gravity acceleration on the surface of Mars is different from that on the surface of the Earth and is only 3.71m / s 2 ,The component parameterization of gravity is set to -3710sinβ, -3710cosβ, and the amplitude change curve is Amp-G;

[0048] 8.4. Use the loads function to set a thrust load with an amplitude of Amp-F at the center of gravity of the ascender;

[0049] 8.5. Use the EncastreBC function to set fixed boundary conditions at the center of rotation, complete the modeling, and obtain the Mars ascender guidance mechanism model.

[0050] In order to solve the optimization design problem of the Mars ascender's guide mechanism, avoid excessive pitch angular velocity when the ascender leaves the guide rail due to the poor design of the guide mechanism, which will bring difficulties to the GNC flight control strategy and cause the failure of the Mars sampling return mission; it is necessary to study the influence of different slider sizes, the number of slider installations and the installation position on the pitch angular velocity of the ascender when it leaves the guide rail; in order to use the simulation model in Abaqus to calculate different pitch angular velocities, it is necessary to assign material properties to the Mars ascender's guide mechanism model in step 8, divide the mesh, set the dynamic analysis step to obtain the finite element model, and submit the finite element model for analysis; it includes the following steps:

[0051] Step 9: Assign material properties to the riser component, bracket component, slider component, and guide rail component according to the actual materials of the components;

[0052] 9.1. Use the Material function to define the material parameters of the riser, bracket, guide rail and slider components respectively;

[0053] 9.2. Use the Homogeneous Solid Section function to define the cross-sectional properties of the bracket, guide rail, and slider respectively;

[0054] 9.3. Use the Homogeneous Shell Section function to define the cross-sectional properties of the ascender;

[0055] 9.4. Use the Section Assignment function to assign the section properties of 9.2 and 9.3 to the riser, bracket, guide rail, and slider components respectively;

[0056] Step 10: Divide the mesh into each component;

[0057] 10.1. Arrange grid seeds for the ascender parts and bracket parts through the seed Part function;

[0058] 10.2. Arrange grid seeds for guide rails and sliders through the seed Part function;

[0059] 10.3. Generate mesh through generate Mesh;

[0060] Step 11: Create a dynamic analysis step and set the historical field output of the displacement and angular velocity of the ascender's center of gravity set;

[0061] 11.1. Use the Explicit Dynamics Step function to set the dynamics analysis step, that is, to set the total simulation time and incremental step size;

[0062] 11.2. Use the field Output Requests function to set the historical field output of the displacement and angular velocity of the ascender at the center of gravity;

[0063] Step 12: According to steps 9 to 11, assign material properties, divide the mesh and set the dynamic analysis steps to the Mars ascender guide mechanism model established in step 8.5, and then obtain the finite element model of the Mars ascender guide mechanism. Submit the finite element model for analysis, and obtain the pitch angular velocity of the ascender when it leaves the guide rail from the historical field output. Further compare the pitch angular velocities of different finite element models to determine the optimal design parameters of the guide rail slider.

[0064] Beneficial effects:

[0065] 1. The present invention discloses a parametric modeling method for a Mars ascender guidance mechanism, which realizes the parametric modeling of the ascender's thermal launch guide rail slider guidance mechanism by secondary development of the finite element software Abaqus using the Python language. Compared with the traditional GUI modeling method, compared with the original modeling process of several hours, the present invention only needs to run the parametric script in Abaqus to complete the entire modeling process within a few seconds, saving the operator a lot of time and energy, and greatly improving the efficiency of finite element modeling.

[0066] 2. The present invention discloses a parametric modeling method for a Mars ascender guide mechanism, which establishes slider components parametrically, assembles slider components parametrically, and sets contact and connection relationships parametrically. It achieves rapid modeling of guide mechanism models with different slider sizes, numbers of sliders installed, and installation positions simply by modifying variables in Python code. Compared with traditional modeling methods, the parametric modeling process uses programmed operations, which can significantly reduce the error probability of the model.

[0067] 3. The present invention discloses a parametric modeling method for a Mars ascender guidance mechanism, which realizes the application of different gravity loads on Mars compared to the Earth by parameterizing the gravity load. This can solve the problem of reduced reliability of test results caused by the different gravity environments between the ground and the Mars surface.

[0068] 4. The present invention discloses a parametric modeling method for the guidance mechanism of a Mars ascender. By running Python scripts, a large number of finite element models can be quickly generated, and then a large number of numerical examples can be used to optimize the design parameters of the guide rail-slider. This helps to use finite element software to analyze the influence of different guidance mechanism design schemes on the pitch angular velocity of the ascender when it leaves the guide rail, and can avoid the problem of a large amount of cost incurred in verification through experimental methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0070] Figure 1 This is a schematic diagram of the ascender;

[0071] Figure 2 (a) is a schematic diagram of the bracket model. Figure 2 (b) is a schematic diagram of the guide rail model;

[0072] Figure 3 This is a schematic diagram of the slider size parameters;

[0073] Figure 4 This is a schematic diagram of the installation position of the slider;

[0074] Figure 5 It is a schematic diagram of the slider riser, bracket, and guide rail-slider assembly;

[0075] Figure 6 It is a schematic diagram of the contact between the guide rail and the slider;

[0076] Figure 7 Schematic diagram for setting the load amplitude, where: Figure 7 (a) is the change of gravity amplitude over time, Figure 7 (b) is the change of thrust amplitude over time;

[0077] Figure 8 Schematic diagram for applying loads and boundary conditions;

[0078] Fig. 9 This is a schematic diagram of the grid division, where: Fig. 9 (a) is a schematic diagram of the slider grid division. Fig. 9 (b) is a schematic diagram of the guide rail grid division. Fig. 9 (c) Schematic diagram of assembly mesh division;

[0079] Fig.10The 27 finite element models generated by the second set of slider position changes using the parametric script;

[0080] Fig.11 This is a graph showing how the riser's exit angle pitch velocity changes with the installation position of the second set of sliders. DETAILED DESCRIPTION

[0081] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0082] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. In order to better illustrate the objects and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0083] Example

[0084] This example discloses a parametric modeling method for a Mars ascender guidance mechanism, the purpose of which is to analyze the effect of the installation position l1=360mm and l3=1210mm of the first and third groups of sliders on the ascender's vertical angle of 30° on the surface of Mars, the slider size parameters are determined as length L=80mm, total height H=16mm, lower side height H1=6.45mm, inclined angle α=30°, lower bottom width D1=19mm, and top surface width D2=14.6mm when assembling N=3 groups of sliders, and changing the installation position l2 of the second group of sliders to analyze the effect of the installation position l2 of the second group of sliders on the ascender's exit pitch angular velocity.

[0085] This example discloses a parametric modeling method for a Mars ascender guidance mechanism, and the specific implementation steps are as follows:

[0086] Step 1: Create and import the riser, bracket and rail components;

[0087] 1.1. Create component models; the components include: fairing, payload compartment, second-stage tank, second-stage solid rocket engine, interstage, first-stage tank, first-stage solid rocket engine;

[0088] 1.2. Assemble the component models created in 1.1 to obtain the ascender components and save them in sat format;

[0089] 1.3. Use the Part From Geometry File function to import the ascender components in 1.2. The ascender components are as follows: Figure 1 As shown;

[0090] 1.4. Create the models of the bracket and guide rail components respectively and save them in sat format;

[0091] 1.5. Use the Part From Geometry File function to import the bracket and rail components of 1.4. The bracket components are as follows: Figure 2 As shown in (a), the guide rail components are as follows Figure 2 (b)

[0092] Step 2: Determine the slider parameter variables required for modeling and create the slider component parametrically;

[0093] 2.1. The slider parameter variables include: length L = 80mm, total height H = 16mm, lower side height H1 = 6.45mm, bevel angle α = 30°, lower bottom width D1 = 19mm, top surface width D2 = 14.6mm. The slider size parameter diagram is as follows: Figure 3 As shown;

[0094] 2.2. Set the current window sketching state through the set Primary Object function;

[0095] 2.3. Use the Line function to input the coordinates (0,0), (19,0), (19,16), (4.4,16), (4.4,8.65), (0,6.45), and (0,0) in sequence to complete the plane sketch of the slider section and obtain the plane sketch;

[0096] 2.4. Use the Base Solid Extrude function to stretch the plane sketch in 2.3 into a slider component with a length of L = 80;

[0097] Step 3: Assemble the bracket, rails and riser;

[0098] 3.1. Add the bracket components and guide rail components in 1.5 to the assembly interface through the Instance function;

[0099] 3.2. Use the translate function to move the guide rail to the position where the guide rail is installed in the bracket to achieve the assembly of the two;

[0100] 3.3. Use the Radial Instance Pattern function to move the other rail symmetrically to the corresponding position of the bracket;

[0101] 3.4. Add the ascender component in 1.3 to the assembly interface through the Instance function;

[0102] 3.5. Assemble the ascender component and the bracket component through the translate function;

[0103] Step 4: Determine the parameter variables required for the slider assembly and parameterize the assembly slider;

[0104] 4.1. The parameter variables required for assembly include: the number of slider groups N = 3, the installation positions of the first and third slider groups l1 = 360 mm, l3 = 1210 mm, the installation position of the second slider group l2 = 785 + 25 × (i-13), i = 0, 1, ..., 25, 26, and the slider installation positions are as follows: Figure 4 As shown;

[0105] 4.2. Use the Instance function to add three more slider components to the assembly interface;

[0106] 4.3. Use the translate function to move the first group of slider components to a position 360 mm from the left end of the guide rail, and move the third group of slider components to a position 1210 mm from the left end of the guide rail. Use the range function to traverse the variable i at the initial position of the parametric modeling script, i = 0, 1, ..., 25, 26, and move the second group of slider components to a position l2 = 785 + 25 × (i-13) from the left end of the guide rail.

[0107] 4.4. Use the Radial Instance Pattern function to symmetrically assemble the three sliders to the corresponding positions of the guide rail on the other side to complete the parametric assembly of the sliders; obtain the assembly of the Mars ascender guide mechanism, as shown in Figure 5 As shown;

[0108] Step 5: Set a collection for each component in the assembly and set rigid body constraints; the components are the riser, bracket, guide rail and slider;

[0109] 5.1. Use the Reference Point function to set reference points at the center of gravity of the ascender and slider and the center of rotation of the bracket;

[0110] 5.2. Use the local function to set the reference point in 5.1 to the corresponding reference point set;

[0111] 5.3. Use the get By Bounding Sphere function to define the ascender, bracket, two guide rails and six slider components as sets with the same name;

[0112] 5.4. Use the Rigid Body function to select the center of gravity of the ascender and the ascender set to set the ascender as a rigid body; select the rotation center of the bracket and the bracket set to set the bracket as a rigid body; select the rotation center of the bracket and the guide rail set to set the two guide rails as rigid bodies;

[0113] 5.5. Use the range function to traverse the six sliders, and use the Rigid Body function to select the center of gravity of the current slider and the slider set to set the six sliders as rigid bodies in turn;

[0114] Step 6: Parameterize and determine the contact surfaces and connection surfaces of each component; the contact surfaces are the surfaces of each component that need to be set up for face-to-face contact; the connection surfaces are the surfaces that need to be set up for binding constraints;

[0115] 6.1. Use the range function to traverse the three sliders on the left side of the ascender, use the find At function to select the top surface of each slider bound to the ascender, and use the Surface function to define the top surface as the connection surface surf-tie-xL. Similarly, use the find At function to select the four side surfaces and one bottom surface of the slider in contact with the guide rail, and use the Surface function to define them as contact surfaces surf-1-xL, surf-2-xL, surf-3-xL, surf-4-xL and surf-5-xL, where x ranges from 0 to 3. Similarly, use the range function to define the connection surfaces of the three sliders on the right side of the ascender as surf-tie-xR, and the contact surfaces as surf-1-xR, surf-2-xR, surf-3-xR, surf-4-xR and surf-5-xR, where x ranges from 0 to 3.

[0116] 6.2. Use find At and Surface functions to set the outer surface of the ascender as the connection surface between the slider and the ascender, surf-tie-MAV;

[0117] 6.3. Use find At and Surface functions to define the surfaces in contact with the slider in the guide rail component. The four side surfaces and bottom surfaces of the left guide rail of the ascender in contact with the slider are defined as contact surfaces surf-daogui-1-L, surf-daogui-2-L, surf-daogui-3-L, surf-daogui-4-L, and surf-daogui-5-L, respectively. The four side surfaces and bottom surfaces of the other guide rail in contact with the slider are defined as contact surfaces surf-daogui-1-R, surf-daogui-2-R, surf-daogui-3-R, surf-daogui-4-R, and surf-daogui-5-R, respectively.

[0118] 6.4. Use find At and Surface functions to define the connection surfaces surf-tie-daogui-L and surf-tie-daogui-R in the guide rail component that are bound to the bracket, and the connection surfaces surf-tie-tuojia-L and surf-tie-tuojia-R in the bracket component that are bound to the guide rail;

[0119] Step 7: Parameterize the contact surface and connection surface parameterized in step 6, and set the contact relationship and connection relationship;

[0120] 7.1. For the contact situation of the guide rail and slider on the left side of the ascender, use the range function to traverse the five contact surfaces, and use the range function to traverse the three sliders for each contact surface. Use the Surface ToSurface Contact Exp function to establish a surface-to-surface contact relationship between the five contact surfaces of each slider and the corresponding contact surface of the guide rail, that is, set the contact surfaces surf-ixL and surf-daogui-iL as surface-to-surface contact pairs, where i is 1 to 5 and x is 1 to 3; similarly, set the contact relationship between the guide rail and the slider on the right side of the ascender; the contact situation between the slider and the guide rail is as follows Figure 6 As shown;

[0121] 7.2. Use the tie function to establish binding constraints between the guide rail and the bracket, that is, set the connecting surfaces surf-tie-daogui-L and surf-tie-tuojia-L as binding constraints, and set the connecting surfaces surf-tie-daogui-R and surf-tie-tuojia-R as binding constraints;

[0122] 7.3. Use the tie function to establish binding constraints between the ascender and the six sliders. That is, use the range function to traverse the three sliders and set the left connecting surfaces surf-tie-xL and surf-tie-MAV as binding constraints. Similarly, set the right connecting surfaces surf-tie-xR and surf-tie-MAV as binding constraints, where the value of x is 1 to 3.

[0123] Step 8: Parametrically apply gravity load, set thrust load and boundary conditions, and complete parametric modeling;

[0124] 8.1. Apply gravity load to the ascender. The key parameter of gravity load is the vertical angle β = 30°;

[0125] 8.2. Use Tabular Amplitude function to define the gravity amplitude change curve Amp-G and thrust amplitude change curve Amp-F. The setting of Amp-G is as follows: Figure 7 As shown in (a), the settings of Amp-F are as follows Figure 7 (b)

[0126] 8.3. In order to solve the problem that the different gravity environments on the ground and on Mars may lead to a decrease in the reliability of the results, the gravity is defined for the assembly using the Gravity function. The gravity acceleration on the surface of Mars is different from that on the surface of the Earth and is only 3.71m / s 2 ,The component parameterization of gravity is set to -1850 and -3213, and the amplitude variation curve is Amp-G;

[0127] 8.4. Use the loads function to set a thrust load with an amplitude of Amp-F at the center of gravity of the ascender;

[0128] 8.5. Use the EncastreBC function to set fixed boundary conditions at the guide rail rotation center to complete the modeling. The schematic diagram of load and boundary condition settings is as follows: Figure 8 shown.

[0129] Step 9: Assign material properties to the riser component, bracket component, slider component, and guide rail component according to the actual materials of the components;

[0130] 9.1. Use the Material function to define the material parameters of the riser, bracket, guide rail, and slider. The guide rail, bracket, and slider are all made of Ti alloy, and the density, Young's modulus, and Poisson's ratio are set to 4.51×10 -9 , 110000, 0.3; the ascender material is LY12 aluminum alloy, and the density, Young's modulus, and Poisson's ratio are set to 2.78×10 -9 , 70000, 0.3;

[0131] 9.2. Use the Homogeneous Solid Section function to define the cross-sectional properties of the bracket, guide rail, and slider respectively;

[0132] 9.3. Use the Homogeneous Shell Section function to define the cross-sectional properties of the ascender;

[0133] 9.4. Use the Section Assignment function to assign the section properties of 9.2 and 9.3 to the riser, bracket, guide rail, and slider components respectively;

[0134] Step 10: Divide the mesh into each component;

[0135] 10.1. Use the seed Part function to arrange grid seeds with a global size of 20 for the ascender component and the bracket component;

[0136] 10.2. The contact between the guide rail and the slider needs to be considered. Therefore, the seed Part function is used to arrange a grid seed with a global size of 2 for the guide rail and the slider. The grid division of the slider is as follows: Fig. 9 (a) shows the mesh division of the guide rail. Fig. 9 (b)

[0137] 10.3. Generate a mesh through generate mesh; the mesh division of the assembly is as follows Fig. 9 (c)

[0138] Step 11: Create a dynamic analysis step and set the historical field output of the displacement and angular velocity of the ascender's center of gravity set;

[0139] 11.1. Use the Explicit Dynamics Step function to set the dynamics analysis step, that is, set the total simulation time to 4.431 and the incremental step size to 0.0001;

[0140] 11.2. Use the field Output Requests function to set the historical field output of the displacement and angular velocity of the ascender at the center of gravity;

[0141] Step 12: Run the parameterization script in Abaqus to obtain 27 finite element models generated due to the change of the second set of slider positions, such as Fig.10 As shown in the figure, 27 finite element models were submitted for finite element analysis, and 27 different ascender exit pitch angular velocities can be obtained from the historical field output of the 27 models. The change of the exit pitch angular velocity of the ascender with the installation position of the slider is shown in the figure. Fig.11 shown.

[0142] In the above embodiment, the parametric assembly slider method of step 4 is applied, and only the value of variable l2 needs to be changed in the Python code to realize the establishment of the guide mechanism model of the second group of sliders in different installation positions, and the establishment of 27 simulation models is completed within 20 seconds; the parameterized application of gravity load in step 8 solves the problem that the different gravity environments of the ground and the fire surface may lead to a decrease in the reliability of the results; the 27 models are submitted for finite element simulation in step 12, and the following are obtained. Fig.10The graph of the riser's exit angle pitch velocity changing with the slider installation position shows that when the second group of sliders is at 760mm, the minimum pitch angular velocity of -4.13° / s is achieved. This proves that the size of the pitch angular velocity of the three-group slider installation method can be optimized according to the position of the second group of sliders, and that the optimal installation position for the current slider size is 760mm from the left end of the guide rail. This can guide the physical optimization design of the Mars ascender's guide mechanism, reduce the pitch angular velocity of the Mars ascender when it leaves the guide rail, and thereby reduce the difficulty of the GNC control strategy in the initial stage of the ascender, thereby improving the success rate of the Mars sample return mission.

[0143] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A parametric modeling method for a Mars ascender guidance mechanism, characterized in that: The following steps are included: Step 1: Create and import the riser, bracket and rail components; 1.

1. Create component models; the components include: fairing, payload compartment, second-stage tank, second-stage solid rocket engine, interstage, first-stage tank, first-stage solid rocket engine; 1.

2. Assemble the component models created in 1.1 to obtain the ascender components and save them in sat format; 1.

3. Use the Part From Geometry File function to import the ascender parts in 1.2; 1.

4. Create the models of the bracket and guide rail components respectively and save them in sat format; 1.

5. Use the Part From Geometry File function to import the bracket and guide rail parts of 1.4; Step 2: Determine the slider parameter variables required for modeling and create the slider component parametrically; 2.

1. The slider parameter variables include: slider length L, slider total height H, slider lower side height H1, slider slope angle α, slider bottom width D1 and top width D2; 2.

2. Set the current window sketching state through the set Primary Object function; 2.

3. Use the Line function to input the coordinates (0,0), (D1,0), (D1,H), (D1-D2,H), (D1-D2,H1+(D1-D2)×sinα), (0,H1), (0,0) in sequence to complete the plane sketch of the slider section and obtain the plane sketch; 2.

4. Use the Base Solid Extrude function to stretch the plane sketch in 2.3 into a slider component with a length of L; Step 3: Assemble the bracket, rails and riser; 3.

1. Add the bracket components and guide rail components in 1.5 to the assembly interface through the Instance function; 3.

2. Use the translate function to move the guide rail to the position where the guide rail is installed in the bracket to achieve the assembly of the two; 3.

3. Use the Radial Instance Pattern function to move the other rail symmetrically to the corresponding position of the bracket; 3.

4. Add the ascender component in 1.3 to the assembly interface through the Instance function; 3.

5. Assemble the ascender component and the bracket component through the translate function; Step 4: Determine the parameter variables required for the slider assembly and parameterize the assembly slider; 4.

1. The parameter variables required for assembly include: the number of slider groups N, the installation position of the slider, that is, the position of each slider from the left end of the guide rail l1, l2, ..., l N ; 4.

2. Continue to add N slider components to the assembly interface through the Instance function; 4.

3. Use the translate function to move the N slider components to the positions l1, l2, …, l away from the left end of the guide rail. N location; 4.

4. Use the Radial Instance Pattern function to symmetrically assemble the N sliders to the corresponding positions of the guide rail on the other side to complete the parametric assembly of the sliders; obtain the assembly of the Mars ascender guide mechanism; Step 5: Set a collection for each component in the assembly and set rigid body constraints; the components are the riser, bracket, guide rail and slider; 5.

1. Use the Reference Point function to set reference points at the center of gravity of the ascender and slider and the center of rotation of the bracket; 5.

2. Use the local function to set the reference point in 5.1 to the corresponding reference point set; 5.

3. Use the get By Bounding Sphere function to define the ascender, bracket, two guide rails and 2N slider components as sets with the same name; 5.

4. Use the Rigid Body function to select the center of gravity of the ascender and the ascender set to set the ascender as a rigid body; select the rotation center of the bracket and the bracket set to set the bracket as a rigid body; select the rotation center of the bracket and the guide rail set to set the two guide rails as rigid bodies; 5.

5. Use the range function to traverse the 2N sliders, and use the Rigid Body function to select the center of gravity of the current slider and the slider set to set the 2N sliders as rigid bodies in turn; Step 6: Parameterize and determine the contact surfaces and connection surfaces of each component; the contact surfaces are the surfaces of each component that need to be set up for face-to-face contact; the connection surfaces are the surfaces that need to be set up for binding constraints; 6.

1. Use the range function to traverse the N sliders on the left side of the ascender, use the find At function to select the top surface of each slider bound to the ascender, and use the Surface function to define the top surface as the connection surface surf-tie-xL. Similarly, use the find At function to select the four side surfaces and one bottom surface of the slider in contact with the guide rail, and use the Surface function to define them as contact surfaces surf-1-xL, surf-2-xL, surf-3-xL, surf-4-xL and surf-5-xL, where x ranges from 0 to N. Similarly, use the range function to define the connection surfaces of the N sliders on the right side of the ascender as surf-tie-xR, and the contact surfaces as surf-1-xR, surf-2-xR, surf-3-xR, surf-4-xR and surf-5-xR, where x ranges from 0 to N. 6.

2. Use find At and Surface functions to set the outer surface of the ascender as the connection surface between the slider and the ascender, surf-tie-MAV; 6.

3. Use find At and Surface functions to define the surfaces in contact with the slider in the guide rail component. The four side surfaces and bottom surfaces of the left guide rail of the ascender in contact with the slider are defined as contact surfaces surf-daogui-1-L, surf-daogui-2-L, surf-daogui-3-L, surf-daogui-4-L, and surf-daogui-5-L, respectively. The four side surfaces and bottom surfaces of the other guide rail in contact with the slider are defined as contact surfaces surf-daogui-1-R, surf-daogui-2-R, surf-daogui-3-R, surf-daogui-4-R, and surf-daogui-5-R, respectively. 6.

4. Use find At and Surface functions to define the connection surfaces surf-tie-daogui-L and surf-tie-daogui-R in the guide rail component that are bound to the bracket, and the connection surfaces surf-tie-tuojia-L and surf-tie-tuojia-R in the bracket component that are bound to the guide rail; Step 7: Parameterize the contact surface and connection surface parameterized in step 6, and set the contact relationship and connection relationship; 7.

1. For the contact situation of the guide rail and slider on the left side of the ascender, use the range function to traverse the five contact surfaces, and use the range function to traverse the N sliders for each contact surface. Use the Surface ToSurface Contact Exp function to establish a surface-to-surface contact relationship between the five contact surfaces of each slider and the corresponding contact surface of the guide rail, that is, set the contact surfaces surf-ixL and surf-daogui-iL as surface-to-surface contact pairs, where i is 1 to 5 and x is 1 to N; set the contact relationship between the guide rail and slider on the right side of the ascender in the same way; 7.

2. Use the tie function to establish binding constraints between the guide rail and the bracket, that is, set the connecting surfaces surf-tie-daogui-L and surf-tie-tuojia-L as binding constraints, and set the connecting surfaces surf-tie-daogui-R and surf-tie-tuojia-R as binding constraints; 7.

3. Use the tie function to establish binding constraints between the ascender and the 2N sliders; that is, use the range function to traverse the N sliders, set the left connecting surfaces surf-tie-xL and surf-tie-MAV as binding constraints, and similarly set the right connecting surfaces surf-tie-xR and surf-tie-MAV as binding constraints, where the value of x is 1 to N; Step 8: Parametrically apply gravity load, set thrust load and boundary conditions, and complete parametric modeling; 8.

1. Apply gravity load to the ascender. The key parameter of gravity load is the vertical angle β. 8.

2. Use Tabular Amplitude function to define the gravity amplitude change curve Amp-G and thrust amplitude change curve Amp-F; 8.

3. Use the Gravity function to define the Martian surface gravity for the assembly; 8.

4. Use the loads function to set a thrust load with an amplitude of Amp-F at the center of gravity of the ascender; 8.

5. Use the EncastreBC function to set fixed boundary conditions at the center of rotation, complete the modeling, and obtain the Mars ascender guidance mechanism model.

2. A parametric modeling method for a Mars ascender guide mechanism according to claim 1, characterized in that: It also includes the following steps, Step 9: Assign material properties to the riser component, bracket component, slider component, and guide rail component according to the actual materials of the components; 9.

1. Use the Material function to define the material parameters of the riser, bracket, guide rail and slider components respectively; 9.

2. Use the Homogeneous Solid Section function to define the cross-sectional properties of the bracket, guide rail, and slider respectively; 9.

3. Use the Homogeneous Shell Section function to define the cross-sectional properties of the ascender; 9.

4. Use the Section Assignment function to assign the section properties of 9.2 and 9.3 to the riser, bracket, guide rail, and slider components respectively; Step 10: Divide the mesh into each component; 10.

1. Arrange grid seeds for the ascender parts and bracket parts through the seed Part function; 10.

2. Arrange grid seeds for guide rails and sliders through the seed Part function; 10.

3. Generate mesh through generate Mesh; Step 11: Create a dynamic analysis step and set the historical field output of the displacement and angular velocity of the ascender's center of gravity set; 11.

1. Use the Explicit Dynamics Step function to set the dynamics analysis step, that is, to set the total simulation time and incremental step size; 11.

2. Use the field Output Requests function to set the historical field output of the displacement and angular velocity of the ascender at the center of gravity; Step 12: According to steps 9 to 11, assign material properties, divide the mesh and set the dynamic analysis steps to the Mars ascender guidance mechanism model established in step 8.5, and then obtain the finite element model of the Mars ascender guidance mechanism. Submit the finite element model for analysis, and obtain the pitch angular velocity of the ascender when it leaves the guide rail from the historical field output. Further compare the pitch angular velocities of different finite element models to determine the optimal parameters of the guide rail slider.

3. A parametric modeling method for a Mars ascender guide mechanism according to claim 1 or 2, characterized in that: In step 8.3, the gravitational acceleration on the surface of Mars is only 3.71 m / s 2 The component parameterization of gravity is set to -3710sinβ, -3710cosβ, and the amplitude change curve is Amp-G.

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