Method for optimizing the number and location of battery pack fixation points

Abstract

The application discloses a kind of optimization method of battery pack fixing point quantity and position, comprising: the finite element model of body-in-white and battery pack is built;According to the finite element model of body-in-white, the basic stiffness of body-in-white is analyzed;In the finite element model of body-in-white, battery pack fixing point is arranged in high-density mode;Different stiffness index constraints are set, a group of parameter optimization is run, the optimal key fixing point quantity and optimal initial position are determined;According to the optimization result of optimal key fixing point quantity and optimal initial position, non-key fixing point is deleted, the position variable of key fixing point is set, and the shape optimization of the position of key fixing point is carried out.The optimization method of battery pack fixing point quantity and position of the application finds out the optimal quantity and position of battery pack fixing point for the performance target of battery pack, automatically realizes optimization to the quantity and position of battery pack fixing point, and reduces the workload of manual.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery pack design, and particularly relates to a method for optimizing the number and position of battery pack fixing points. BACKGROUND

[0002] Electric vehicles are a hot spot in the current automobile industry research and development. As one of the three electric systems of electric vehicles, the battery system differs from the other two systems in that the battery pack is strongly connected with the vehicle body structure and can be regarded as a part of the vehicle body structure, thus making an important contribution to the performance of the vehicle body stiffness, strength and the like. According to part of the vehicle model data, compared with the pure white body stiffness, the battery pack contributes up to 40% to 90% to the improvement of the torsional stiffness, and also has a contribution of 15% to 25% to the improvement of the bending stiffness. Reasonably designing the structure of the battery pack and the number and position of the fixing points of the battery pack with the vehicle body is an important way to improve the contribution of the battery pack to the performance of the vehicle body stiffness.

[0003] Therefore, there is an urgent need for a method for optimizing the number and position of battery pack fixing points. SUMMARY

[0004] The present application aims to provide a method for optimizing the number and position of battery pack fixing points to solve the problems in the prior art, and to automatically optimize the number and position of battery pack fixing points and reduce the manual workload.

[0005] The present application provides a method for optimizing the number and position of battery pack fixing points, which comprises the following steps.

[0006] Building a finite element model of the white vehicle body and the battery pack;

[0007] Analyzing the basic stiffness of the white vehicle body according to the finite element model of the white vehicle body;

[0008] Arranging the battery pack fixing points in a high-density manner in the finite element model of the white vehicle body;

[0009] Setting different stiffness index constraints, running a group of parameter optimizations, and determining the optimal key fixing point number and the optimal initial position;

[0010] According to the optimization results of the optimal key fixing point number and the optimal initial position, deleting the non-key fixing points, setting the position variables of the key fixing points, and performing shape optimization on the positions of the key fixing points.

[0011] The method for optimizing the number and position of battery pack fixing points as described above, wherein preferably, the step of building a finite element model of the white vehicle body and the battery pack specifically comprises the following steps.

[0012] Building a white vehicle body stiffness analysis finite element model;

[0013] A battery pack finite element model is built, and the built battery pack finite element model is added to the body-in-white finite element model.

[0014] The battery pack fixing point number and position optimization method as described above, preferably, the body-in-white stiffness analysis finite element model is built, specifically comprising:

[0015] The translational degrees of freedom of the body-in-white and the chassis rear suspension spring mounting point in the X, Y and Z directions are constrained;

[0016] Two Z-direction concentrated forces with equal size and opposite direction are applied at the front shock absorber mounting of the body-in-white and the chassis, forming a torque around the X axis, and the torque size is 2000N·m;

[0017] The Z-direction freedom of the MPC at the two mounting points of the front shock absorber is constrained, and the absolute value of the relative displacement of the two mounting points in the Z direction is equal.

[0018] The battery pack fixing point number and position optimization method as described above, preferably, the battery pack finite element model is built, and the built battery pack finite element model is added to the body-in-white finite element model, specifically comprising:

[0019] The bolts for connecting the battery pack frame and the body-in-white lower body are simplified to a cylindrical surface composed of shell elements, and the nodes thereof are connected to the battery pack frame and the body-in-white elements through tie, and the distance of tie connection is set to 1.5-2.0 times the average element size.

[0020] The battery pack fixing point number and position optimization method as described above, preferably, the basic stiffness of the body-in-white is analyzed according to the finite element model of the body-in-white, specifically comprising:

[0021] According to the body-in-white stiffness analysis finite element model, the torsion angle θ of the front side of the body-in-white is calculated by the following formula,

[0022] θ=180°arctan((Z1-Z2) / Y) / π (1)

[0023] Wherein, Z1 represents the Z-direction deformation value of the left measuring point, Z2 represents the Z-direction deformation value of the right measuring point, Y is the Y-direction distance between the left measuring point and the right measuring point, and the measuring point is the close point of the X coordinate of the front shock absorber mounting point and the bottom of the front side rail of the body-in-white cabin;

[0024] According to the torsion angle θ of the front side of the body-in-white, the torsional stiffness Kr is calculated by the following formula:

[0025] K r =2000 / θ (2)

[0026] Kr represents torsional stiffness, that is, a value of a torque obtained when a unit angle deformation occurs.

[0027] The method for optimizing the number and position of the battery pack fixing points as described above, wherein preferably, the battery pack fixing points are arranged in a high-density manner in the finite element model of the body-in-white, and specifically comprising:

[0028] The high-density fixing points are arranged at a spacing of 40-60 mm in the feasible fixing point position area of the body-in-white, and the shell element of each fixing point bolt is composed of a separate component, and the elastic modulus E of the material is set separately, and the feasible fixing point position area includes the side sills or cross beams of the lower body.

[0029] The method for optimizing the number and position of the battery pack fixing points as described above, wherein preferably, the different stiffness index constraints are set, and a group of parameter optimizations are performed to determine the optimal number of key fixing points and the optimal initial position, and specifically comprising:

[0030] The elastic modulus E of each bolt component is set as a discrete variable, and the variable value range is set as a minimum value and a maximum value, if the optimization result is the minimum value, it indicates that the fixing point is not needed, and is a non-key fixing point, if it is the maximum value, it indicates that the fixing point is needed, and is a key fixing point;

[0031] The optimal number of fixing points is determined by a group of parameter optimizations;

[0032] The sum of the elastic modulus E of all bolt components is used as an optimization constraint condition;

[0033] The parameter optimization is performed to solve the maximum body stiffness, and the optimization result can obtain the maximum body stiffness value and the optimal initial position of the battery pack fixing points under the corresponding number constraint.

[0034] The method for optimizing the number and position of the battery pack fixing points as described above, wherein preferably, the optimal number of fixing points is determined by a group of parameter optimizations, and specifically comprising:

[0035] The corresponding body stiffness under different numbers of fixing points is solved;

[0036] According to the change trend of the body stiffness, the optimal number of fixing points is confirmed,

[0037] The sum of the elastic modulus E of all bolt components is used as an optimization constraint condition, and specifically comprising:

[0038] The optimization constraint condition is that the sum of the elastic modulus E of all bolt components is not greater than n*10e 7 , and n represents the maximum number of constraint fixing points, and the constraint tolerance violation is 0.08%-0.15%.

[0039] The optimization method of the number and position of the battery pack fixing points as described above, wherein, preferably, the optimization is solved with the maximum body stiffness as the target operating parameter, and the optimization result can obtain the maximum body stiffness value corresponding to the number constraint and the optimal initial position of the battery pack fixing points, and specifically includes:

[0040] A series of body stiffness value results are obtained by setting different optimization constraint values, and a corresponding fixing point number-body stiffness maximum value curve is drawn;

[0041] According to the curve change trend of the fixing point number-body stiffness maximum value curve, the fixing point number of the stiffness growth efficiency turning point in the curve is determined as the optimal number of the battery pack fixing points;

[0042] According to the optimal number of the battery pack fixing points, the optimal number constraint corresponding optimization result is found to obtain the corresponding key fixing point initial position.

[0043] The optimization method of the number and position of the battery pack fixing points as described above, wherein, preferably, the optimization result according to the optimal key fixing point number and the optimal initial position is used to delete the non-key fixing points, set the position variable of the key fixing points, and perform shape optimization on the position of the key fixing points, and specifically includes:

[0044] According to the optimization result, the non-key fixing point components are deleted, and all the elastic modulus variables and optimization constraints corresponding to the non-key fixing point components are deleted, the elastic modulus of the key fixing point components is set to a maximum value, so that the key fixing point components are approximately rigidly connected;

[0045] The grid deformation is used to define that each key fixing point can move within a preset range, the optimized key fixing point can move within a range of ±(40mm-60mm), and each moving distance is defined as a shape variable;

[0046] The optimization target is adjusted to the maximum stiffness.

[0047] The present application provides an optimization method of the number and position of battery pack fixing points, which finds the optimal number and position of battery pack fixing points for the performance target of the battery pack, automatically optimizes the number and position of the battery pack fixing points, and reduces the manual workload; identifies the number and position of key fixing points through the combination of various optimization methods; confirms the number and preliminary position of key fixing points through a group of parameter optimization of high-density battery pack fixing points and the influence trend of different number of fixing points on the body stiffness performance; and obtains the optimal accurate position of key fixing points through shape optimization of the position of key fixing points. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described below in conjunction with the drawings, in which:

[0049] Figure 1 The flow chart of the embodiment of the optimization method of the number and position of the battery pack fixing points provided by the present application;

[0050] Figure 2 The white body torsional rigidity working condition schematic diagram;

[0051] Figure 3 The battery pack fixing schematic diagram;

[0052] Figure 4 The battery pack and the threshold of one fixing point structure schematic diagram;

[0053] Figure 5 The high-density arrangement of the fixing points schematic diagram;

[0054] Figure 6 The fixing point number-body rigidity maximum value curve;

[0055] Figure 7 The optimization schematic diagram of the fine position of the battery pack fixing points. DETAILED DESCRIPTION

[0056] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative in nature and is in no way intended to limit the disclosure, its application or uses. The present disclosure can be implemented in numerous different forms, not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangement of the components and steps set forth in these embodiments, the components of the materials, the numerical expressions and values should be interpreted as merely exemplary, rather than as a limitation.

[0057] The "first", "second" and similar words used in the present disclosure do not represent any order, number or importance, but are only used to distinguish different parts. "Include" or "contain" and similar words mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements. "Up", "down" and the like are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0058] In the present disclosure, when it is described that a specific component is located between a first component and a second component, there can be or can not be an intervening component between the specific component and the first component or the second component. When it is described that a specific component is connected to another component, the specific component can be directly connected to the another component without an intervening component, or can not be directly connected to the another component with an intervening component.

[0059] All the terms used in the present disclosure, including technical terms or scientific terms, have the same meanings as understood by those skilled in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that the terms defined in general dictionaries should be interpreted in the meanings consistent with the meanings in the context of related technologies, and should not be interpreted in idealized or excessively formalized meanings, unless otherwise explicitly defined herein.

[0060] The techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification where appropriate.

[0061] The number and position of the current battery pack fixing points are designed by referring to the arrangement spacing and position of the corresponding fixing points of the existing vehicle models, combining with experience and manually arranging, and then carrying out simulation analysis verification and comparison. The disadvantage is that the ideal number and position of the battery pack fixing points of different vehicle models are different, and manual arrangement often cannot find the optimal design. Moreover, the battery pack fixing points include the combination of fixing point position and number variables, which requires a large amount of design scheme analysis and verification comparison, and the workload is large.

[0062] As shown in Figure 1 The battery pack fixing point number and position optimization method provided by the embodiment specifically includes the following steps in the actual execution process:

[0063] Step S1, building a finite element model of the body-in-white and the battery pack.

[0064] In an embodiment of the battery pack fixing point number and position optimization method of the present disclosure, the step S1 can specifically include:

[0065] Step S11, building a body-in-white stiffness analysis finite element model.

[0066] As shown in Figure 2 In an embodiment of the battery pack fixing point number and position optimization method of the present disclosure, the step S11 can specifically include:

[0067] Step S111, constraining the translational degrees of freedom of X, Y and Z directions at the body-in-white and the rear suspension spring mounting point of the chassis.

[0068] Step S112: Apply two Z-axis concentrated forces of equal magnitude and opposite direction to the shock absorber mounting points in front of the body-in-white and the chassis to form a torque around the X-axis with a torque magnitude of 2000 N·m.

[0069] In other embodiments of the present invention, the torque around the X-axis can be other values, such as 1800 N·m, 2000 N·m, etc., and the present invention does not specifically limit it.

[0070] Step S113: Constrain the Z-direction degree of freedom of the MPC (multi-point rigid constraint) at the two mounting points of the front shock absorber so that the absolute values ​​of the relative Z-direction displacements at the two mounting points are equal.

[0071] Step S113 ensures that the vehicle body only undergoes torsional deformation around the X-axis.

[0072] Step S12: Build the finite element model of the battery pack and add the built finite element model of the battery pack to the finite element model of the body-in-white.

[0073] like Figure 3 As shown, in actual structures, battery pack fixing is typically achieved by bolting the battery pack frame to the left and right side sills and front and rear crossbeams of the lower body of the vehicle body. Specifically, in this invention, Figure 4 The diagram illustrates a typical cross-sectional structure at the junction of the battery pack frame and the door sill. During finite element model construction, to facilitate later optimization, the bolts connecting the battery pack frame and the left and right door sills and front and rear crossbeams of the lower body of the vehicle were simplified to cylindrical surfaces composed of shell elements. These bolts were then connected to the battery pack frame and body-in-white elements via tie connections. The tie connection distance was set to 1.5-2.0 times (e.g., 1.8 times) the average element size. The advantage of this connection is that during optimization, the solver can automatically search for the nearest battery pack frame and body-in-white element nodes to the bolt nodes and establish connections. These connections can be updated during the optimization iteration process.

[0074] Step S2: Analyze the basic stiffness of the body-in-white based on the finite element model of the body-in-white.

[0075] In one embodiment of the method for optimizing the number and location of battery pack fixing points according to the present invention, step S2 may specifically include:

[0076] Step S21: Based on the finite element model of the body-in-white stiffness analysis, calculate the torsional angle θ at the front of the body-in-white using the following formula.

[0077] θ=180°arctan((Z1-Z2) / Y) / π (1)

[0078] Wherein, Z1 represents the Z-direction deformation value of the left measuring point, Z2 represents the Z-direction deformation value of the right measuring point, Y is the Y-direction distance between the left measuring point and the right measuring point, and the measuring point is the close point of the X coordinate of the bottom of the front side frame and the front shock absorber mounting point of the body-in-white.

[0079] Step S22, according to the torsion angle θ of the front side of the body-in-white, the torsion stiffness Kr is calculated by the following formula:

[0080] K r = 2000 / θ (2)

[0081] K r represents the torsion stiffness, that is, the torque value under unit angle deformation is obtained.

[0082] After analyzing a certain type of body-in-white according to the above working condition, the Z-direction positions of the two sides are 1.18 mm and -1.19 mm respectively, the Y-direction distance between the two measuring points is 940 mm, and the torsion stiffness of the body-in-white is 2000 / (180*arctan((1.18-(-1.19)) / 940) / π), that is, Kr=13745 N·m / °. The stiffness index after adding the battery pack will increase the basic stiffness by a certain amount.

[0083] Step S3, arranging the battery pack fixing points in a high-density manner in the finite element model of the body-in-white.

[0084] Specifically, high-density fixing points are arranged at an interval of 40-60 mm (for example, 50 mm) in the feasible fixing point position area of the body-in-white, and the shell element of each fixing point bolt constitutes a separate part, and the elastic modulus E of the material is separately set, and the feasible fixing point position area includes the left and right rocker or cross beam of the lower vehicle body. The elastic modulus E is equivalent to the connection strength, so that the battery pack will be arranged with hundreds of fixing points. It should be noted that the arrangement interval of the fixing points is not specifically limited in the present application.

[0085] The bolt is simplified as a cylindrical surface composed of shell elements, and the optimization of the elastic modulus is only one kind of connection and optimization method, and in other embodiments of the present application, a spring can be used to connect the battery pack frame and the left and right rocker and front and rear cross beam structure of the lower vehicle body of the body-in-white, and in this case, it is also feasible to optimize the spring stiffness and the like.

[0086] Step S4, setting different stiffness index constraints and running a group of parameter optimizations to determine the optimal number and optimal initial position of the key fixing points.

[0087] In one embodiment of the optimization method of the number and position of the battery pack fixing points of the present application, the step S4 can specifically include:

[0088] Step S41, the elastic modulus E of each bolt component is set as a discrete variable, and the variable value range is set as a minimum value and a maximum value. If the optimization result is the minimum value, it indicates that the fixed point does not need to be fixed, and it is a non-critical fixed point. If it is the maximum value, it indicates that the fixed point needs to be fixed, and it is a critical fixed point.

[0089] Exemplarily, the minimum value is taken as 10, and the maximum value is taken as 10e7. It needs to be noted that the present application does not specifically limit the values of the minimum value and the maximum value.

[0090] Step S42, the optimal number of fixed points is determined through a group of parameter optimization.

[0091] In an embodiment of the method for optimizing the number and position of the fixed points of the battery pack, the step S42 can specifically include:

[0092] Step S421, the corresponding body stiffness under different numbers of fixed points is solved.

[0093] Step S422, the optimal number of fixed points is confirmed according to the change trend of the body stiffness.

[0094] Step S43, the sum of the elastic modulus E of all bolt components is taken as the optimization constraint condition.

[0095] Specifically, the optimization constraint condition is that the sum of the elastic modulus E of all bolt components is not greater than n*10e 7 , where n represents the maximum number of constraint fixed points, and the constraint violation tolerance is 0.08%-0.15% (for example, 0.1%). If the optimization constraint is that the sum of all variables is not greater than 15*10e7 (with a constraint violation tolerance of 0.1%), the number of constraint fixed points is not greater than 15.

[0096] Step S44, the optimization is solved with the maximum body stiffness as the target operating parameter, and the optimization result can obtain the maximum body stiffness value under the corresponding number of constraints and the optimal initial position of the battery pack fixed point.

[0097] In an embodiment of the method for optimizing the number and position of the fixed points of the battery pack, the step S44 can specifically include:

[0098] Step S441, a series of body stiffness value results are obtained by setting different optimization constraint values, and a corresponding fixed point number-body stiffness maximum value curve (for example, as shown in Figure 6 ).

[0099] Step S442, the number of fixed points of the stiffness growth efficiency turning point in the curve is determined according to the curve change trend of the fixed point number-body stiffness maximum value curve, as the optimal number of battery pack fixed points.

[0100] by Figure 6 Taking the curve shown as an example, based on the trend of the curve, it can be determined that a high stiffness growth efficiency can still be maintained when the number of fixed points in the figure is 24; when the number exceeds 24, the stiffness growth efficiency decreases significantly. Therefore, it can be confirmed that the optimal number of fixed points is 24.

[0101] Step S443: Based on the optimal number of battery pack fixing points, find the optimization result corresponding to the optimal number constraint to obtain the initial position of the corresponding key fixing points.

[0102] After determining the optimal number of fixed points, the optimization result corresponding to the optimal number constraint can be found, and the initial position of the corresponding key fixed points can be obtained.

[0103] Step S5: Based on the optimization results of the optimal number of key fixed points and the optimal initial position, delete non-key fixed points, set the position variables of key fixed points, and optimize the shape of the positions of key fixed points.

[0104] After determining the optimal number and initial position of key fixing points through the first stage of optimization, the second stage of optimization further optimizes the shape of the fine positions of the battery pack fixing points. In one embodiment of the method for optimizing the number and position of battery pack fixing points of the present invention, step S5 may specifically include:

[0105] Step S51: Based on the optimization results, delete non-critical fixed point components and delete all elastic modulus variables and optimization constraints corresponding to non-critical fixed point components. Set the elastic modulus of critical fixed point components to a maximum value (e.g., 10e7) so that the critical fixed point components are approximately rigidly connected.

[0106] Step S52: Use mesh deformation to define that each key fixed point can move within a preset range. Define the optimized key fixed point to be able to move within a range of ±(40mm-60mm), and define each movement distance as a shape variable.

[0107] like Figure 7 As shown, if the spacing between high-density fixed points is set to 50mm in step S3, the optimized key fixed points can be moved within a range of ±50mm.

[0108] Step S53: Adjust the optimization objective to maximize stiffness.

[0109] With the above settings, the second stage of optimization is shape optimization, which seeks the optimal position for each key fixing point within ±50mm of its original location, aiming to maximize stiffness. Running shape optimization will yield the optimal and precise position for each key fixing point.

[0110] The battery pack fixing point quantity and position optimization method provided by the embodiment of the application finds the optimal quantity and position of the battery pack fixing points, automatically optimizes the quantity and position of the battery pack fixing points, and reduces the manual workload; the combination of multiple optimization methods is used to identify the key fixing point quantity and position; a set of parameter optimizations are performed on the high-density battery pack fixing points, the key fixing point quantity and preliminary position are confirmed through the influence trend of different quantities of fixing points on the body stiffness performance; and the key fixing point position is optimized in shape to obtain the optimal accurate position of the key fixing point.

[0111] So far, the embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein according to the above description.

[0112] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or some technical features can be replaced equivalently without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A method for optimizing the number and location of fixing points in a battery pack, characterized in that, include: Build finite element models of the body-in-white and battery pack; Based on the finite element model of the body-in-white, the basic stiffness of the body-in-white is analyzed; In the finite element model of the body-in-white, the battery pack mounting points are arranged in a high-density manner; By setting different stiffness index constraints and running a set of parameter optimizations, the optimal number and optimal initial position of the key fixing points of the battery pack fixing points are determined. Based on the optimization results of the optimal number and optimal initial position of key fixed points, non-key fixed points are deleted, the position variables of key fixed points are set, and the position of key fixed points is optimized in shape.

2. The method for optimizing the number and location of battery pack fixing points according to claim 1, characterized in that, The construction of the finite element model of the body-in-white and battery pack specifically includes: Build a finite element model for stiffness analysis of the body-in-white; Build a finite element model of the battery pack and add the built finite element model of the body-in-white to it.

3. The method for optimizing the number and location of battery pack fixing points according to claim 2, characterized in that, The construction of the finite element model for stiffness analysis of the body-in-white specifically includes: Constrain the translational degrees of freedom in the X, Y, and Z directions at the mounting points of the body-in-white and the rear suspension springs of the chassis; Two equal and opposite Z-axis concentrated forces are applied at the shock absorber mounting points in front of the body-in-white and chassis, generating a torque of 2000 around the X-axis. ; The Z-axis degree of freedom of the front shock absorber is constrained by multiple rigid constraints at the two mounting points, so that the absolute values ​​of the relative Z-axis displacements at the two mounting points are equal.

4. The method for optimizing the number and location of battery pack fixing points according to claim 2, characterized in that, The process of building a finite element model of the battery pack and adding the built finite element model of the body-in-white specifically includes: The bolts used to connect the battery pack frame and the left and right side sills and front and rear crossbeams of the lower body of the white body are simplified into cylindrical surfaces composed of shell units, and their nodes are connected to the battery pack frame and white body units by tie. The distance of the tie connection is set to 1.5-2.0 times the average unit size.

5. The method for optimizing the number and location of battery pack fixing points according to claim 3, characterized in that, The analysis of the basic stiffness of the body-in-white based on the finite element model of the body-in-white specifically includes: Based on the finite element model of the body-in-white stiffness analysis, the torsional angle at the front of the body-in-white is calculated using the following formula. , （1） Where Z1 represents the Z-direction deformation value of the left measuring point, Z2 represents the Z-direction deformation value of the right measuring point, Y is the Y-direction distance between the left and right measuring points, and the measuring point is the point close to the X coordinate of the bottom of the front longitudinal beam of the white body engine compartment and the front shock absorber mounting point. Based on the torsion angle of the front side of the body-in-white The torsional stiffness is calculated using the following formula. The formula is as follows: （2） This represents torsional stiffness, which is the torque value obtained when a unit angle deformation occurs.

6. The method for optimizing the number and location of battery pack fixing points according to claim 1, characterized in that, The arrangement of battery pack mounting points in a high-density manner in the finite element model of the body-in-white specifically includes: High-density fixing points are arranged at 40mm-60mm intervals in the feasible fixing point location area of ​​the body-in-white, and the shell unit of each fixing point bolt forms a separate component with the elastic modulus E of the material set separately. The feasible fixing point location area includes the side sills or crossbeams of the lower body.

7. The method for optimizing the number and location of battery pack fixing points according to claim 4, characterized in that, The process of setting different stiffness index constraints and running a set of parameter optimizations to determine the optimal number and optimal initial position of key fixing points for the battery pack includes: The elastic modulus E of each bolt component is set as a discrete variable, and the variable takes a range of a minimum and a maximum value. If the optimization result is a minimum value, it means that the fixed point is not needed and is a non-critical fixed point. If it is a maximum value, it means that the fixed point is needed and is a critical fixed point. The optimal number of critical fixing points for the battery pack is determined by optimizing a set of parameters. The sum of the elastic moduli E of all bolt components is used as the optimization constraint. The optimization solution is performed with the target operating parameter being the maximum body stiffness. The optimization result can obtain the maximum body stiffness value and the optimal initial position of the key fixed point of the battery pack under the corresponding quantity constraints.

8. The method for optimizing the number and location of battery pack fixing points according to claim 7, characterized in that, The process of determining the optimal number of critical fixing points for the battery pack through a set of parameter optimization specifically includes: Solve for the vehicle body stiffness under different numbers of key fixed points; Based on the changing trend of vehicle body stiffness, determine the optimal number of key fixed points. The optimization constraint, which uses the sum of the elastic moduli E of all bolt components, specifically includes: The optimization constraint is that the sum of the elastic moduli E of all bolt components is not greater than 1. ,but This indicates the maximum number of constraint fixed points, with a constraint violation tolerance of 0.08%-0.15%.

9. The method for optimizing the number and location of battery pack fixing points according to claim 7, characterized in that, The optimization solution, which uses the maximum vehicle body stiffness as the objective operating parameter, yields the optimal initial positions of the maximum vehicle body stiffness and key fixed points of the battery pack under the corresponding quantity constraints. Specifically, this includes: By setting different optimization constraint values, a series of body stiffness values ​​are obtained, and the corresponding curve of the number of fixed points - the maximum body stiffness value is plotted. Based on the trend of the curve of number of fixed points - maximum body stiffness, determine the number of fixed points at the inflection point of stiffness growth efficiency in the curve, which is the optimal number of key fixed points for the battery pack. Based on the optimal number of key fixed points in the battery pack, find the optimization result corresponding to the optimal number constraint, and obtain the initial position of the corresponding key fixed points.

10. The method for optimizing the number and location of battery pack fixing points according to claim 6, characterized in that, Based on the optimization results of the optimal number and optimal initial position of key fixed points, non-key fixed points are deleted, position variables of key fixed points are set, and the position of key fixed points is optimized in shape. Specifically, this includes: Based on the optimization results, non-critical fixed-point components are deleted, along with all elastic modulus variables and optimization constraints corresponding to them. The elastic modulus of the critical fixed-point components is set to a maximum value to make the critical fixed-point components approximately rigidly connected. The mesh deformation is used to define that each key fixed point can move within a preset range, and each movement distance is defined as the position variable of the key fixed point; The optimization objective was adjusted to maximize stiffness.

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