Calculation method for load conversion of local coordinate system

Abstract

The invention relates to a calculation method for load conversion of a local coordinate system, and the method is based on a part simulation model, and comprises the following steps: S1, determining a hard point coordinate of a part; s2, establishing a local coordinate system; s3, establishing a local coordinate load calculation formula: F < x > Local = a * F < x > Globe + b * F < y > Globe + c * F < z > Globe; s4, setting boundary conditions; s5, solving a coefficient; the method has the advantages that a model of the part does not need to be arranged during calculation, calculation can be carried out only through the hard point position, specific simulation analysis software is not needed, calculation is easy, the calculation amount is reduced, the calculation capacity is high, calculation efficiency is improved, large-scale and batch mechanical analysis calculation of the automobile part can be carried out, and the method is suitable for popularization and application. The application range is wide and the practical value is high.

Description

Technical Field

[0001] The invention relates to the technical field of structural component simulation, and in particular to a calculation method for local coordinate system load conversion. Background Art

[0002] During the development and design of automotive parts, simulation analysis and calculations need to be performed in the component's own coordinate system. During the component verification phase, bench tests are required to verify the actual performance of the component.

[0003] In both cases, it is necessary to load the load in the local coordinate system of the component's hard points, such as key installation points, the center of the kinematic hinge, and the installation point of the bushing center. In the early stage of the design process, engineers can obtain the load in the global vehicle coordinate system of the hard point position through mechanical decomposition, so it is necessary to convert the load in the global vehicle coordinate system into the load in the component's own local coordinate system. At present, the method of converting the load in the 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 a high level of software expertise, and this method does not have wide applicability.

[0004] In summary, there is an urgent need for a method to convert the load of the global vehicle coordinate system into the load of the component's own local coordinate system, so as to quickly, efficiently and accurately obtain the load under the local coordinate system to complete the design work of the component. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a calculation method for local coordinate system load conversion, which establishes a local coordinate system through a hard point, loads the unit loads in the X, Y, and Z directions of the global vehicle through the local coordinate system to obtain the X, Y, and Z direction forces of the local coordinate system, uses the force of the local coordinate system to obtain the coefficient, and finally obtains the hard point local coordinate system load. The method has high accuracy, and can obtain accurate loads after coordinate system conversion by solving the coefficient. It is simple and convenient, does not require the establishment of a three-dimensional model, is not restricted to a certain moment of simulation analysis software, reduces the professional requirements for engineers, reduces the amount of calculation, and improves the calculation efficiency. It can carry out large-scale batch mechanical analysis and calculation of automotive parts, improves the design speed, and improves the design accuracy.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for calculating load conversion in a local coordinate system is provided. The method is based on a component simulation model and comprises the following steps:

[0008] S1: Determine the hard point coordinates of the components and establish rigid units to connect the hard points;

[0009] S2: Establish a local coordinate system. Establish the local coordinate system of the component itself based on the hard point position. Take one hard point as the origin of the local coordinate system. The direction of the rigid unit between the hard points establishes the x-axis direction of the local coordinate system.

[0010] S3: Establish the calculation formula. The calculation formula for the local coordinate load is:

[0011] F xLocal =a·F xGlobal +b·F yGlobal +c·F zGlobal

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

[0013] F xGlobal 、F yGlobal 、F zGlobal They are the forces in the X, Y and Z directions under the vehicle coordinates respectively;

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

[0015] S4: Set boundary conditions, constrain the hard point at the origin of the local coordinate system, constrain its six degrees of freedom, and load unit forces in the three directions of X, Y, and Z of the global vehicle coordinate system at another hard point connected to the rigid unit, submit the mechanical processing operation, and obtain the force of the hard point loaded with the global unit force in the X, Y, and Z directions of the local coordinate system through post-processing;

[0016] S5: Solve the coefficient. When only the load in the X direction of the vehicle coordinate system is loaded, that is, F is loaded xGlobal =1N, then F yGlobal and F zGlobal All are 0, and the mechanical solution post-processing operation is performed. By extracting the support reaction force in the local coordinate system at the hard point, F xLocal , calculate and obtain F xLocal Substituting the data into the formula in S3, we can see that F xLocal =a, and then we get coefficient a, and so on, we can get coefficients b and c;

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

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

[0019] Furthermore, the rigid unit is a unit with two hard points fixedly connected.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This method is easy to operate. It does not require setting up the model of parts during calculation. It only needs to calculate through the hard point position. The model is simple to establish, the calculation is simple, the amount of calculation is reduced, the calculation ability is strong, and the calculation efficiency is improved. It can be used for large-scale batch mechanical analysis and calculation of automobile parts.

[0022] 2. This method does not require any specific simulation analysis software. Any three-dimensional calculation software based on simulation design can be used. It does not require engineers to have high professionalism. It has a wide range of applications and high practical value.

[0023] 3. This method has high accuracy. By solving the coefficients, the load after coordinate system conversion can be accurately obtained. The solution is simple and fast. It can be used for large-scale batch mechanical analysis and calculation of automotive parts, improve design speed and design accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of establishing a local coordinate system provided by the present invention.

[0025] Figure 2 It is a schematic diagram of the hard point positions of components provided by the present invention.

[0026] Figure 3 It is a schematic diagram of the simulation calculation boundary conditions provided by the present invention.

[0027] Figure 4 It is a schematic diagram of the forces acting on the hard points in various directions provided by the present invention.

[0028] Figure 5 It is a schematic diagram of strength analysis of a connecting rod using a vehicle coordinate system load provided by the present invention.

[0029] Figure 6 It is a schematic diagram of strength analysis of a connecting rod using a local coordinate system load provided by the present invention.

[0030] Figure 7 This is a diagram of a control arm model provided by the present invention.

[0031] Figure 8 It is a schematic diagram of strength analysis of a control arm using a vehicle coordinate system load provided by the present invention.

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

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

[0034] [Example 1]

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

[0036] Hard Point X direction Y direction Z direction C1 -172N 11454N 1637N

[0037] 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 unit.

[0038] Step S2: Figure 2 As shown, the local coordinate system of the connecting rod itself is established, the C2 coordinate is the origin of the local coordinate system, and the X-axis of the local coordinate system is the direction of the line connecting the two hard points.

[0039] Step S3: Establish a calculation formula, F xLocal =a·F xGlobal +b·F yGlobal +c·F zGlobal .

[0040] Step S4: Figure 3 As shown in the figure, the boundary conditions are set to constrain the hard point C2, constrain its 6 degrees of freedom, and load the unit forces in the three directions of the vehicle coordinate system X, Y, and Z at the hard point C1, that is, load F at the hard point C1 position respectively. xGlobal =1N, F zGlobal =1N, F zGlobal = 1N; then submit the mechanical solution for post-processing operation, and obtain the force acting on the hard point C1 in each direction of the local coordinate system through post-processing, that is, the F of the hard point C1 xLocal 、F yLocal、 F zLocal The value of Figure 4 shown.

[0041] Step S5: Solve the coefficient. When only the load in the X direction of the vehicle coordinate system is loaded, that is, load F xGlobal =1N, then F yGlobal and F zGlobal All are 0, and the mechanical solution post-processing operation is performed. By extracting the support reaction force in the local coordinate system at the hard point, F xLocal , calculate and obtain F xLocal Substituting the data into the formula in S3, we can see that F xLocal=a, and then we get the coefficient a, and so on, we can get the coefficients b and c, that is, the coefficients a=0.0548, b=-0.9908, c=-0.1239.

[0042] Step S6: load conversion in local coordinates. According to the load of the vehicle coordinate system at the hard point C1 and the coefficient values ​​of a, b, and c obtained in S4, the load in the local coordinate system at the hard point C1 is calculated, F xLocal =0.0548×(-172)+(0.9908)×(11454)+(-0.1239)×1637=-11560.623N.

[0043] Step S7: Figure 5-Figure 6 As shown in the figure, the accuracy of load conversion is verified, the load of the whole vehicle coordinate system is used to perform strength analysis and calculation on the connecting rod, and then the converted local coordinate load is used to perform strength calculation on the connecting rod, and the two results are compared. It can be seen from the stress distribution cloud diagram that the stress size and position are basically consistent. The load of the local coordinate system obtained by this method is highly feasible and accurate.

[0044] [Example 2]

[0045] like Figure 7 As shown, taking the control arm of a certain vehicle model as an example, the road spectrum load of the vehicle coordinate at the hard point C1 is converted into the road spectrum load in the local coordinate system of the control arm itself. The method specifically includes the following steps:

[0046] Step S1: Determine the hard point coordinates and connect the two hard points by establishing a rigid unit.

[0047] Step S2: Establish the local coordinate system of the connecting rod itself, and the X-axis of the local coordinate system is the direction of the line connecting the two hard points.

[0048] Step S3: Establish a calculation formula, F xLocal =a·F xGlobal +b·F yGlobal +c·F zGlobal .

[0049] Step S4: Set boundary conditions, constrain hard point C2, constrain its six degrees of freedom, and load unit forces in the three directions of the vehicle coordinate system X, Y, and Z at hard point C1, that is, load F at the position of hard point C1. xGlobal =1N, F zGlobal =1N, F zGlobal = 1N; then submit the mechanical solution for post-processing operation, and obtain the force acting on the hard point C1 in each direction of the local coordinate system through post-processing, that is, the F of the hard point C1 xLocal 、F yLocal、 F zLocal The value of Figure 4 shown.

[0050] Step S5: Solve the coefficient. When only the load in the X direction of the vehicle coordinate system is loaded, that is, load F xGlobal =1N, then F yGlobal and F zGlobal All are 0, and the mechanical solution post-processing operation is performed. By extracting the support reaction force in the local coordinate system at the hard point, F xLocal , calculate and obtain F xLocal Substituting the data into the formula in S3, we can see that F xLocal =a, and then we get the coefficient a, and so on, we can get the coefficients b and c.

[0051] Step S6: load conversion in local coordinates. According to the load of the vehicle coordinate system at the hard point C1 and the coefficient values ​​a, b, c obtained in S4, the load in the local coordinate system at the hard point C1 is obtained by calculation.

[0052] Step S7: Figure 8-Figure 9 As shown in the figure, the accuracy of load conversion is verified, the vehicle coordinate system load is used to perform fatigue analysis and calculation on the control arm, and then the converted local coordinate load is used to perform fatigue calculation on the connecting rod, and the two results are compared. It can be seen from the life cloud diagram that the size and position of fatigue damage are basically consistent, which proves that the method is feasible and accurate.

[0053] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A calculation method for load conversion in a local coordinate system, based on a component simulation model, characterized in that: The calculation method of the local coordinate system load conversion comprises the following steps: S1: Determine the hard point coordinates of the components and establish rigid units to connect the hard points; S2: Establish a local coordinate system. Establish the local coordinate system of the component itself based on the hard point position. Take one hard point as the origin of the local coordinate system. The direction of the rigid unit between the hard points establishes the X-axis direction of the coordinate axis of the local coordinate system. S3: Establish the calculation formula. The calculation formula for the local coordinate load is: F xLocal =a·F xGlobal +b·F yGlobal +c·F zGlobal Where: F xLocal is the X-direction load in the local coordinate system; F xGlobal 、F yGlobal 、F zGlobal They are the forces in the X, Y and Z directions under the vehicle coordinates respectively; a, b, and c are the corresponding coefficients respectively; S4: Set boundary conditions, constrain the hard point at the origin of the local coordinate system, constrain its six degrees of freedom, and load unit forces in the three directions of X, Y, and Z of the global vehicle coordinate system at another hard point connected to the rigid unit, submit the mechanical processing operation, and obtain the force of the hard point loaded with the global unit force in the X, Y, and Z directions of the local coordinate system through post-processing; S5: Solve the coefficient. When only the load in the X direction of the vehicle coordinate system is loaded, that is, F is loaded xGlobal =1N, then F yGlobal and F zGlobal All are 0, and the mechanical solution post-processing operation is performed. By extracting the support reaction force in the local coordinate system at the hard point, F xLocal , calculate and obtain F xLocal Substituting the data into the formula in S3, we can see that F xLocal =a, and then we get coefficient a, and so on, we can get coefficients b and c; S6: Load conversion in local coordinates. According to the load of the vehicle coordinate system at the hard point and the coefficient values ​​of a, b, and c obtained in S5, the load in the local coordinate system at the hard point is obtained by calculation.

2. The calculation method for local coordinate system load conversion according to claim 1 is characterized in that: The hard point is the point in the structural component that determines its kinematic characteristics.

3. The calculation method for local coordinate system load conversion according to claim 1 is characterized in that: The rigid unit is a unit with two hard points fixedly connected.

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