Calculation method for load transformation in local coordinate system

Abstract

The present invention relates to a calculation method for load transformation in a local coordinate system. The calculation method for load transformation in a local coordinate system is based on a part simulation model, and comprises the following steps: S1: determining hard point coordinates of a part; S2: establishing a local coordinate system; S3: establishing a local coordinate load calculation formula: FxLocal=a•FxGlobal+b•FyGlobal+c•FzGlobal; S4: setting boundary conditions; S5: solving coefficients; and S6: performing load transformation in the local coordinate system. The present invention has the following beneficial effects: no part model is required during calculation, and the calculation can be performed solely on the basis of hard point positions, without relying on any specific simulation analysis software, the calculation is simple, the calculation amount is reduced, the calculation capability is strong, and the calculation efficiency is improved, large‑scale and batch mechanical analysis calculation of automobile parts can be performed, the application range is wide, and the practical value is high.

Description

A calculation method for local coordinate system load conversion TECHNICAL FIELD

[0001] The present application relates to the technical field of structural component simulation, in particular to a calculation method for local coordinate system load conversion. BACKGROUND

[0002] In the development and design process of automobile components, simulation analysis and calculation need to be carried out in the local coordinate system of the components themselves, and in the verification stage of the components, bench tests need to be carried out on the components to verify the actual use performance of the components.

[0003] Both of the above two cases need to load the load in the local coordinate system of the components themselves at the positions of the hard points of the components, such as key mounting points, motion hinge center points, and mounting points of bushing centers, etc. However, at the initial stage of the design process, engineers can obtain the load in the global vehicle coordinate system at the positions of the hard points through mechanical decomposition, so it is necessary to convert the load in the global vehicle coordinate system into the load in the local coordinate system of the components themselves. At present, the method for converting the load in the global vehicle coordinate system into the load in the local coordinate system is usually to use professional mechanical system dynamics simulation software for analysis and operation, which requires engineers to have high software professionalism, and this method does not have wide applicability.

[0004] In summary, there is an urgent need for a method for converting the load in the global vehicle coordinate system into the load in the local coordinate system of the components themselves to quickly and efficiently and accurately obtain the load in the local coordinate system to complete the design work of the components.

[0005] SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the present application provides a calculation method for local coordinate system load conversion, which establishes a local coordinate system through a hard point, loads unit loads in the X, Y and Z directions of the global vehicle through the local coordinate system to obtain the acting forces in the X, Y and Z directions of the local coordinate system, uses the acting forces in the local coordinate system to obtain a coefficient, and finally obtains the local coordinate system load of the hard point. This method has high accuracy, can obtain the load after coordinate system conversion through the way of solving the coefficient, is simple and convenient, does not need to establish a three-dimensional model, is not limited to a certain simulation analysis software, reduces the requirement for the professionalism of engineers, reduces the amount of operation, improves the calculation efficiency, can be used for large-scale batch mechanical analysis and calculation of automobile components, improves the design speed and improves the design precision.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] A calculation method for local coordinate system load conversion, which is based on a component simulation model and includes the following steps:

[0009] S1: determine the hard point coordinates of the component, and connect the hard points by establishing rigid elements;

[0010] S2: establish a local coordinate system, establish a local coordinate system of the component itself at the hard point position, take a hard point as the origin of the local coordinate system, and establish the coordinate axis x-axis direction of the local coordinate system by the direction of the rigid element between the hard points;

[0011] S3: establish a calculation formula, the local coordinate load calculation formula is: xLocal = a·F xGlobal + b·F yGlobal + c·F zGlobal

[0012] In the formula: F xLocal is the X-direction load in the local coordinate system;

[0013] F xGlobal , F yGlobal , and F zGlobal are the X, Y, and Z-direction forces in the global coordinate system, respectively;

[0014] a, b, and c are corresponding coefficients, respectively;

[0015] S4: set boundary conditions, constrain the hard point at the origin position of the local coordinate system in 6 degrees of freedom, and load unit forces in the X, Y, and Z directions of the global coordinate system at the other hard point connected by the rigid element, respectively, submit the mechanical processing operation, and obtain the X, Y, and Z-direction forces of the hard point loaded with global unit forces in the local coordinate system through post-processing;

[0016] S5: solve the coefficients, when only loading the X-direction load of the global coordinate system, i.e. loading F xGlobal = 1N, at this time F yGlobal and F zGlobal are both 0, perform mechanical post-processing operation, and obtain F xLocal by extracting the local coordinate system of the hard point, bring the F xLocal data obtained by calculation into the formula in S3, it can be known that F xLocal = a, and then the coefficient a is obtained, and in this way the coefficients b and c can be obtained;

[0017] S6: load conversion in the local coordinate system, according to the load of the global coordinate system at the hard point and the a, b, and c coefficient values obtained in S5, the load in the local coordinate system at the hard point is obtained by calculation.

[0018] Further, the hard point refers to a point in a structural component that determines its kinematic characteristics.

[0019] Further, the rigid element is a fixed connection element between two hard points.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The method is easy to operate, and does not need to set the model of the parts during calculation, but can be calculated through the hard point position, so that the model is simple to establish, the calculation is simple, the operation amount is reduced, the operation capacity is strong, the calculation efficiency is improved, and large-scale batch automobile parts mechanical analysis and calculation can be performed.

[0022] 2. The method does not need to be performed by a specific simulation analysis software, and can be used based on three-dimensional operation software of simulation design, without the need for engineers to have high professionalism, so that the application range is wide and the practical value is high.

[0023] 3. The method has high accuracy, and the load after the coordinate system conversion can be accurately obtained through the solving of the coefficient, the solving method is simple and rapid, large-scale batch automobile parts mechanical analysis and calculation can be performed, the design speed is improved, and the design precision is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 is a schematic diagram of a local coordinate system provided by the present application.

[0025] Fig. 2 is a schematic diagram of a hard point position of a part provided by the present application.

[0026] Fig. 3 is a schematic diagram of a simulation calculation boundary condition provided by the present application.

[0027] Fig. 4 is a schematic diagram of a force in each direction of a hard point provided by the present application.

[0028] Fig. 5 is a schematic diagram of a strength analysis of a connecting rod by a whole vehicle coordinate system load provided by the present application.

[0029] Fig. 6 is a schematic diagram of a strength analysis of a connecting rod by a local coordinate system load provided by the present application.

[0030] Fig. 7 is a model diagram of a control arm provided by the present application.

[0031] Fig. 8 is a schematic diagram of a strength analysis of a control arm by a whole vehicle coordinate system load provided by the present application.

[0032] Fig. 9 is a schematic diagram of a strength analysis of a control arm by a local coordinate system load provided by the present application. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application are further described below:

[0034]

Example 1

[0035] As shown in Figure 1, taking the rear control link of a certain vehicle model as an example, the vehicle global coordinate system load at hard point C1 is converted into a local coordinate system load. The vehicle global coordinate system load is shown in the table, and the method comprises the following steps:

[0036] Step S1: Determine the hard point coordinates, the hard point C1 coordinates are (2725.170, -701.220, -114.610), and the hard point C2 coordinates are (2709.680, -421.230, -79.600). The two hard points are connected by establishing a rigid element.

[0037] Step S2: As shown in Figure 2, a local coordinate system of the link itself is established, and the C2 coordinates are the origin of the local coordinate system, and the X axis of the local coordinate system is the connecting line direction of the two hard points.

[0038] Step S3: Establish a calculation formula, F xLocal =a·F xGlobal +b·F yGlobal +c·F zGlobal .

[0039] Step S4: As shown in Figure 3, set the boundary conditions, constrain the hard point C2 in six directions, and load the unit forces of the X, Y, and Z directions of the vehicle coordinate system at the hard point C1, i.e. load F xGlobal =1N, F zGlobal =1N, and F zGlobal =1N at the hard point C1, respectively; then submit the mechanical solution post-processing operation, and obtain the forces of the hard point C1 in each direction of the local coordinate system, i.e. the values of F xLocal , F yLocal、 , and F zLocal , as shown in Figure 4.

[0040] Step S5: Solve the coefficients. When only the X direction load of the vehicle coordinate system is loaded, i.e. F xGlobal =1N, F yGlobal and F zGlobal are both 0, perform the mechanical solution post-processing operation, and obtain F xLocal by extracting the support reaction force at the hard point in the local coordinate system. The F xLocal data obtained by calculation is brought into the formula in S3, and it is known that F xLocal =a, and the coefficient a is obtained. In this way, the coefficients b and c are obtained, i.e. the coefficients a=0.0548, b=-0.9908, and c=-0.1239.

[0041] Step S6: Local coordinate load conversion, according to the load of the whole vehicle coordinate system at the hard point C1 and the a, b, c coefficient values obtained in S4, the load at the hard point C1 in the local coordinate system is obtained by calculation, F xLocal = 0.0548 * (-172) + (0.9908) * (11454) + (-0.1239) * 1637 = -11560.623 N.

[0042] Step S7: As shown in FIGS. 5-6, verify the accuracy of the load conversion, apply the whole vehicle coordinate system load to the strength analysis calculation of the connecting rod, and then apply the converted local coordinate load to the strength calculation of the connecting rod, and compare the results of the two, the stress distribution cloud map can see that the stress size and position are basically the same, the local coordinate system load obtained by this method has high feasibility and high accuracy.

[0043] [Example 2]

[0044] As shown in FIG. 7, taking the control arm of a certain vehicle as an example, the road spectrum load of the whole vehicle coordinate at the hard point C1 is converted into the road spectrum load under the local coordinate system of the control arm itself, and the method specifically includes the following steps:

[0045] Step S1: Determine the hard point coordinates, connect the two hard points by establishing a rigid element.

[0046] Step S2: Establish the local coordinate system of the connecting rod itself, and the X axis of the local coordinate system is the connecting direction of the two hard points.

[0047] Step S3: Establish the calculation formula, F xLocal = a·F xGlobal +b·F yGlobal +c·F zGlobal .

[0048] Step S4: Set the boundary conditions, constrain the hard point C2, constrain its 6 degrees of freedom, and load the unit force of the whole vehicle coordinate system X, Y, Z three directions at the hard point C1, that is, load F xGlobal = 1 N, F zGlobal = 1 N, F zGlobal = 1 N at the hard point C1 position; then submit the mechanical solution post-processing operation, and obtain the force of each direction of the hard point C1 in the local coordinate system through post-processing, that is, obtain the values of F xLocal , F yLocal、 F zLocal of the hard point C1, as shown in FIG. 4.

[0049] Step S5: Solve the coefficients, when only loading the whole vehicle coordinate system X direction load, that is, loading F xGlobal = 1 N, F yGlobal and F zGlobalAll are 0, and the mechanical solution post-processing operation is performed, and the support reaction force under the local coordinate system at the hard point can be obtained F xLocal F is obtained by calculation xLocal The data is brought into the formula in S3, and F xLocal =a, and the coefficient a is obtained, and the coefficients b and c can be obtained in the same way.

[0050] Step S6: local coordinate load conversion, according to the load of the whole vehicle coordinate system at the hard point C1 and the coefficient values a, b and c obtained in S4, the load under the local coordinate system at the hard point C1 is obtained by calculation.

[0051] Step S7: as shown in FIGS. 8-9, the accuracy of the load conversion is verified, the fatigue analysis calculation of the control arm is performed by applying the load of the whole vehicle coordinate system, the fatigue calculation of the connecting rod is performed by applying the converted local coordinate load, and the results of the two are compared, and the life cloud map can show that the fatigue damage size and position are basically consistent, thereby proving that the method has high feasibility and high accuracy.

[0052] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical solution and concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for calculating a local coordinate system load transformation, the method being based on a simulation model of a component, characterized in that, The local coordinate system load conversion calculation method comprises the following steps: S1: determining the hard point coordinates of the parts, and connecting the hard points by establishing rigid elements; S2: establishing a local coordinate system, establishing a local coordinate system of the part itself at the hard point position, taking a hard point as the origin of the local coordinate system, and establishing the coordinate axis X axis direction of the local coordinate system in the direction of the rigid element connecting the hard points; S3: establishing a calculation formula, and the local coordinate load calculation formula is: F xLocal = a · F xGlobal + b · F yGlobal + c · F zGlobal In the formula: F xLocal is the X-direction load in the local coordinate system; F xGlobal , F yGlobal , F zGlobal are the forces in the X, Y, Z directions under the vehicle coordinates, respectively; a, b and c are corresponding coefficients; S4: setting boundary conditions, restraining the hard point at the origin position of the local coordinate system in six direction freedoms, and loading unit forces in the X, Y and Z directions of the global vehicle coordinate system at the other hard point connected by the rigid element, submitting the mechanical processing operation, and obtaining the forces in the X, Y and Z directions of the local coordinate system of the hard point loaded with the global unit force through post-processing; S5: Solve the coefficient, when only loading the whole vehicle coordinate system X direction load, that is, loading F xGlobal = 1N, at this time F yGlobal and F zGlobal are 0, after the mechanical solution post-processing operation, the support reaction force under the local coordinate system at the hard point can be obtained F xLocal , the calculated F xLocal data is brought into the formula in S3, it can be known that F xLocal = a, and the coefficient a is obtained, and the coefficients b and c can be obtained in the same way; S6: local coordinate load conversion, obtaining the load of the hard point in the local coordinate system by calculation according to the load of the hard point in the global vehicle coordinate system and the a, b and c coefficient values obtained in S5.

2. The method of claim 1, wherein, The hard point refers to a point in a structural part that determines the kinematic characteristics thereof.

3. The method of claim 1, wherein, The rigid element is a fixed connection element of two hard points.

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