A composite front air suspension optimization design method

Abstract

The invention relates to the technical field of vehicle manufacturing, and discloses a composite front air suspension optimization design method. The invention first calculates the theoretical stiffness of a leaf spring, then gradually determines the coordinates of the center point where the leaf spring is connected to a fixed end support, the fixed center point where an airbag is connected to an upper cover plate of the leaf spring, and the center point where the leaf spring is connected to a lifting lug end support, and then respectively designs the structures of the upper cover plate of the leaf spring, the fixed end support, the lifting lug end support, and the leaf spring, so that the actual stiffness of the leaf spring is consistent with the calculated theoretical stiffness, and finally checks the strength of the structure of the entire front suspension; wherein the Y-axis coordinate of the fixed center point where the airbag is connected to the upper cover plate of the leaf spring is an optimal value obtained through analysis, and the Z-axis coordinate of the center point where the leaf spring is connected to the fixed end support and the center point where the leaf spring is connected to the lifting lug end support are optimal values ​​obtained through analysis, so that the front suspension designed by the invention has reasonable installation positions of the leaf spring and the airbag, and the leaf spring has little influence on the steering wheel during movement.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle manufacturing, and in particular to an optimization design method for a composite front air suspension. Background Art

[0002] There are generally two types of air suspensions used in heavy trucks: full airbag air suspension and compound air suspension. Compound air suspension uses a unique guide structure, the most common of which is to use leaf springs as the guide mechanism, which has the advantages of simple structure, reliability, and relatively low cost.

[0003] The composite front air suspension is jointly loaded by leaf springs and airbags. The installation positions of leaf springs and airbags have an important impact on the use of the entire composite front air suspension. If the leaf springs and airbags are installed in an improper position, the leaf springs will be improperly stressed, affecting their shock absorbing effects and easily causing damage to the leaf springs. In addition, the leaf springs will have an excessive impact on the steering wheel during movement, seriously affecting the normal driving of the vehicle. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a composite front air suspension optimization design method, according to which the installation positions of the leaf spring and the airbag obtained are reasonable, and the leaf spring has little influence on the steering wheel during movement.

[0005] In order to achieve the above-mentioned object, the present invention provides a composite front air suspension optimization design method, the composite front air suspension comprises a frame, a front axle, a leaf spring, an airbag and a leaf spring upper cover plate, the frame is fixedly connected with a fixed end support and a lifting ear end support, one end of the leaf spring is hinged to the fixed end support, the other end of the leaf spring is hinged to the lifting ear end support, the leaf spring is installed on the front axle, the leaf spring upper cover plate is arranged on the leaf spring, the airbag is installed on the leaf spring upper cover plate, the center point of the leaf spring connected to the fixed end support is point a, the fixed center point of the airbag and the leaf spring upper cover plate is point b, and the center point of the leaf spring connected to the lifting ear end support is point c, comprising the following steps:

[0006] S1: Calculate the composite stiffness of the front suspension based on the front axle sprung mass and the front suspension system frequency;

[0007] S2: After the airbag is selected, the composite stiffness of the front suspension obtained in S1 is subtracted from the stiffness of the airbag under standard load to obtain the theoretical stiffness of the leaf spring;

[0008] S3: Establish a rectangular coordinate system with the center point of the front axle of the vehicle as the zero point, wherein the length direction of the vehicle is the X-axis direction, the width direction of the vehicle is the Y-axis direction, and the height direction of the vehicle is the Z-axis direction;

[0009] S4: Determine the X-axis coordinate of point a as x according to the length of the leaf springa And determine the X-axis coordinate of point c as x c According to the width of the front axle and the rotation envelope of the front wheel, the Y-axis coordinate of point a is determined as y a And determine the Y-axis coordinate of point c as y c , according to the height of the front axle from the ground, the Z-axis coordinate of point b is determined as z b ;

[0010] S5: According to the layout of the engine and the rotation envelope of the front wheel, the Y-axis coordinate of point b is determined as y b and determine the layout range of the X-axis coordinate of point b;

[0011] S6: According to the determined x a 、x c ,y a ,y c 、z b and b , a nonlinear CAE analysis model of the front suspension including the airbag and the leaf spring of the initial structure is established, the X-axis coordinate of point b is set as a variable, and the X-axis coordinate of point b is determined as x according to the optimal stress results of the leaf spring obtained when the front suspension is in bending condition and emergency braking condition. b ;

[0012] S7: According to the determined, x a 、x c ,y a ,y c 、z b ,y b and x b , establish a front suspension dynamics analysis model including airbags, leaf springs and steering systems, set the Z-axis coordinates of point a and point c as variables, and determine the Z-axis coordinate of point a as z according to the optimal interference result of the front suspension and steering system during motion. a And determine the Z-axis coordinate of point c as z c ;

[0013] S8: According to the coordinates of point a and point c, the structures of the fixed end support, the eye end support and the leaf spring are designed respectively, so that the actual stiffness of the leaf spring is consistent with the theoretical stiffness obtained in S2;

[0014] S9: Design the upper cover of the leaf spring according to the coordinates of point b;

[0015] S10: Based on the structure designed in S8 and S9, a CAE analysis model is established to check whether the strength of the structure meets the requirements.

[0016] Among them, in S1, according to the formula

[0017]

[0018] Calculate the composite stiffness of the front suspension, where n is the suspension system frequency, C is the suspension stiffness, and M is the sprung mass.

[0019] In S2, the type of the airbag is determined according to the height and load-bearing mass of the airbag.

[0020] Among them, in S6, the optimal stress result of the leaf spring is: in the bending condition, the stress of the leaf spring is the smallest, and in the emergency braking condition, the stress of the leaf spring is less than 90% of the yield strength of the leaf spring.

[0021] Among them, in S7, the optimal interference result of the front suspension and the steering system during movement is that the leaf spring causes the steering wheel to deflect at the minimum angle during movement.

[0022] In S7 , the Z-axis coordinate of point a is the same as the Z-axis coordinate of point c.

[0023] Among them, in S8, the front end of the leaf spring is designed as two pieces.

[0024] The embodiment of the present invention is a composite front air suspension optimization design method. Compared with the prior art, its beneficial effect is that: the present invention first calculates the composite stiffness of the front suspension, and then calculates the theoretical stiffness of the leaf spring after the airbag is selected, and then gradually determines the coordinates of the center point of the connection between the leaf spring and the fixed end support, the fixed center point of the airbag and the upper cover plate of the leaf spring, and the center point of the connection between the leaf spring and the ear end support, and then respectively designs the structures of the upper cover plate of the leaf spring, the fixed end support, the ear end support and the leaf spring, so that the actual stiffness of the leaf spring is consistent with the calculated theoretical stiffness, and finally checks the strength of the structure of the entire front suspension; since the Y-axis coordinate of the fixed center point of the airbag and the upper cover plate of the leaf spring is the optimal value obtained by establishing a nonlinear CAE analysis model of the front suspension, and the Z-axis coordinate of the center point of the connection between the leaf spring and the fixed end support and the center point of the connection between the leaf spring and the ear end support are the optimal values ​​obtained by establishing a front suspension dynamics analysis model, the front suspension designed by the present invention has reasonable installation positions of the leaf spring and the airbag, and the leaf spring has the least influence on the steering wheel during movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a front view of the composite air front suspension of the present invention;

[0026] Figure 2 is a top view of the composite air front suspension of the present invention;

[0027] In the figure, 1, vehicle frame; 2, leaf spring; 3, airbag; 4, upper cover of leaf spring; 5, fixed end support; 6, lifting ear end support; 7, front axle; a, center point of connection between leaf spring and fixed end support; b, fixed center point of airbag and upper cover of leaf spring; c, center point of connection between leaf spring and lifting ear end support. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used in the present invention to indicate the orientation or position relationship is based on the orientation or position relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0030] A composite front air suspension optimization design method according to a preferred embodiment of the present invention comprises a vehicle frame 1, a front axle 7, a leaf spring 2, an air bag 3 and a leaf spring upper cover plate 4 (the leaf spring upper cover plate 4 integrates a leaf spring cover plate, an air bag lower support and a shock absorber lower support), the vehicle frame 1 is fixedly connected with a fixed end support 5 and a lifting ear end support 6, one end of the leaf spring 2 is hinged to the fixed end support 5, the other end of the leaf spring 2 is hinged to the lifting ear end support 6, the leaf spring 2 is installed on the front axle 7, and the leaf spring upper cover plate 4 is arranged on the leaf spring 2, the airbag 3 is installed on the leaf spring upper cover plate 4, the center point of the leaf spring 2 and the fixed end support 5 is point a, the fixed center point of the airbag 3 and the leaf spring upper cover plate 4 is point b, and the center point of the leaf spring 2 and the eye end support 6 is point c. In the above structure, the hard points of the composite front air suspension are mainly point a, point b and point c. After the positions of the three hard points are determined, the mechanism of the composite front air suspension can be basically determined, so the design of the positions of the above three hard points is very important.

[0031] The present invention comprises the following steps:

[0032] S1: The composite stiffness of the front suspension is calculated based on the front axle sprung mass and the front suspension system frequency; wherein the relationship between the front axle sprung mass and the front suspension system frequency is as follows:

[0033]

[0034] In the above formula, n is the suspension system frequency. The recommended value of the front suspension system frequency of a general truck is 1.5HZ-2.0HZ. The composite air front suspension has an airbag added, and its system frequency can be designed to be smaller, which is beneficial to the smoothness of the whole vehicle. It can be designed at 1.5HZ-1.6HZ. C is the suspension stiffness, and M is the sprung mass. M can be obtained by inputting the standard front axle load during vehicle development and design, minus the front axle mass and tire mass.

[0035] S2: After the airbag is selected, the composite stiffness of the front suspension obtained in S1 is subtracted from the stiffness of the airbag at standard load to obtain the theoretical stiffness of the leaf spring; wherein, the selection of the airbag is determined according to the height and load-bearing mass of the airbag. The airbag selection mainly considers the height of the airbag (the highest and lowest dimensions, and generally a margin of more than 20mm is required above and below the airbag). The load-bearing mass of the airbag under a certain pressure can be actually measured. The load-bearing mass of the airbag can be determined according to the airbag load ratio and the system design air pressure. At present, the air pressure of the truck system is generally 7bar. Generally, the load ratio of the front air suspension airbag at standard load can be 90%, that is, 90% of the mass on the front axle spring is borne by the airbag, and the rest is borne by the leaf spring. After the airbag is selected, its stiffness curve parameters have been basically determined (the airbag stiffness curve parameters are obtained by the airbag manufacturer through bench testing). The stiffness of the airbag at standard load is obtained according to the airbag stiffness curve.

[0036] S3: Establish a rectangular coordinate system with the center point of the front axle of the vehicle as the zero point, wherein the length direction of the vehicle is the X-axis direction, the width direction of the vehicle is the Y-axis direction, and the height direction of the vehicle is the Z-axis direction;

[0037] S4: Determine the X-axis coordinate of point a as x according to the length of the leaf spring a And determine the X-axis coordinate of point c as x c According to the width of the front axle and the rotation envelope of the front wheel, the Y-axis coordinate of point a is determined as y a And determine the Y-axis coordinate of point c as y c , according to the height of the front axle from the ground, the Z-axis coordinate of point b is determined as z b; For heavy trucks, the larger the distance between the left and right wheels of the vehicle, the more stable the vehicle is in the left and right directions. However, its maximum value must comply with the mandatory requirements of the national standard GB 1589-2016. Therefore, manufacturers generally take a value close to the maximum value for design. The distance between the left and right leaf springs is generally as large as possible, but it is necessary to avoid the front wheel rotation envelope. Therefore, the maximum outer width of the leaf spring is determined according to the width of the front axle and the wheel rotation envelope, thereby determining the Y-axis coordinate of point a and the Y-axis coordinate of point c; Generally speaking, the longer the length of the leaf spring, the better the vibration reduction, but the cost and weight will increase. The length of the leaf spring generally has a recommended value in the industry. The front leaf spring of a light truck is 33% of the vehicle's wheelbase (the distance between the front and rear axles of the vehicle), and the front leaf spring of a truck is 25%-35% of the vehicle's wheelbase, thus determining the X-axis of point a. The coordinates of point a and point c are the X-axis coordinates; the tire size of the vehicle is generally a fixed value, which determines the height of the wheel center from the ground, and also determines the height of the axle from the ground. The leaf spring is installed on the axle, so the mounting surface height of the leaf spring at the axle is also determined. Between the lower fixing point of the airbag and the leaf spring is the installation space of the lower support of the airbag. The smaller the lower support of the airbag, the lower the cost of parts, and the easier it is to select the airbag. However, it is generally not lower than the upper surface of the U-bolt that fixes the leaf spring, otherwise the airbag will interfere with the U-bolt. That is, the minimum value of point b from the leaf spring to the mounting surface of the axle is the sum of the thickness of the leaf spring, the thickness of the upper cover of the leaf spring, and the diameter of the U-bolt. In this way, the Z-axis coordinate of point b is determined.

[0038] S5: According to the layout of the engine and the rotation envelope of the front wheel, the Y-axis coordinate of point b is determined as y b And determine the layout range of the X-axis coordinate of point b; the airbag skin is generally made of rubber, which should be kept away from heat sources such as the engine as much as possible, and should also avoid the extreme positions of the left and right steering of the front wheels. Therefore, the Y-direction size of the airbag can be basically determined, and the size range of the X-direction can be further reduced.

[0039] S6: According to the determined x a 、x c ,y a ,y c 、z b and b , a nonlinear CAE analysis model of the front suspension including the airbag and the leaf spring of the initial structure is established, the X-axis coordinate of point b is set as a variable, and the X-axis coordinate of point b is determined as x according to the optimal stress results of the leaf spring obtained when the front suspension is in bending condition and emergency braking condition. b; The nonlinear analysis model established in this step includes an airbag and a leaf spring of an initial structure (the leaf spring of the initial structure is a horizontal plate structure, that is, in the CAE analysis model, it is assumed that the Z-axis coordinates of point a and point c are consistent with the Z-axis coordinates of point b. Since it is a comparative analysis, the leaf spring of the initial structure does not affect the conclusion of the analysis). The airbag stiffness should be designed according to the airbag stiffness curve, which is a nonlinear stiffness. In the CAE analysis model, the X-axis coordinate of point b varies within the range determined in S5. When the front suspension is in a bending condition and an emergency braking condition, the stress result of the leaf spring will change with the change of the X-axis coordinate of point b. When the stress result of the leaf spring is the optimal value result, that is, in the bending condition, the stress of the leaf spring is the smallest, and in the emergency braking condition, the stress of the leaf spring is less than 90% of the yield strength of the leaf spring, and its corresponding X-axis coordinate is determined as the X-axis coordinate x of point b. b At this point, the coordinates of the X-axis, Y-axis and Z-axis of point b have been determined, that is, the installation position of the airbag has been determined.

[0040] In one embodiment of the present invention, the analysis results of the CAE analysis model (stress results of the leaf spring) are shown in Table 1:

[0041]

[0042]

[0043] Table 1 Analysis results of nonlinear CAE analysis model of front suspension

[0044] According to the analysis results, when the air spring is placed in front, emergency braking conditions will aggravate the longitudinal torsion of the leaf spring, resulting in serious deformation of the leaf spring and interference with the steering system movement, causing obvious deviation; the stresses of both the airbag rearward arrangement scheme 1 and the airbag rearward arrangement scheme 2 are relatively low, both less than 90% of the yield strength of the leaf spring, meeting the design requirements, but when the airbag rearward arrangement scheme 1 is adopted, the force arm of the airbag lower support is shorter than that of the airbag rearward arrangement scheme 2, the design of the lower support of the airbag rearward arrangement scheme 1 can be relatively light, and this scheme has the smallest leaf spring stress under commonly used heavy-load bending conditions, that is, the result of the airbag rearward arrangement scheme 1 is the optimal result. Therefore, after comprehensive consideration, the airbag rearward arrangement scheme 1 is adopted.

[0045] S7: According to the determined, x a 、x c ,y a ,y c 、z b ,y b and x b , establish a front suspension dynamics analysis model including airbags, leaf springs and steering systems, set the Z-axis coordinates of point a and point c as variables, and determine the Z-axis coordinate of point a as z according to the optimal interference result of the front suspension and steering system during motion. aAnd determine the Z-axis coordinate of point c as z c ;

[0046] A front suspension dynamics analysis model is established. The airbag is arranged according to the position determined in the previous step. The Z-axis coordinates of point a and point c set an optimization analysis range. Then, the rod system and steering wheel model of the steering system are added. The steering system is connected to the front wheel, and the front wheel moves up and down with the axle, and the axle is fixed to the leaf spring. Therefore, the connection point between the steering rod system and the wheel is affected by the deformation of the leaf spring. During the compression of the leaf spring, the axle, wheel and steering rod system will be driven to move together, and the movement of the steering rod system will affect the rotation of the steering wheel. Therefore, there is a movement problem between the movement of the leaf spring and the steering system. The leaf spring is connected to the vehicle. The movement of point a can be understood as taking point a as the rotation center, so the position of point a will affect the movement trajectory of the leaf spring. Previously, the X-axis and Y-axis coordinates of point a have been determined, and the Z-axis coordinate of point c is consistent with the Z-axis coordinate value of point a. Therefore, in this dynamic analysis model, the interference result of the front suspension and steering system during movement changes with the change of the Z-axis coordinate of point a. When the interference result of the front suspension and steering system during movement is the optimal result (at this time, the leaf spring has the least effect on the steering wheel during movement (the steering wheel has the smallest deflection angle), its corresponding Z-axis coordinate is determined as the Z-axis coordinate z of point a. a and the Z-axis coordinate z of point c c At this point, the X-axis, Y-axis, and Z-axis coordinates of point a and point c have been determined.

[0047] S8: According to the coordinates of point a and point c, the structures of the fixed end support, the eye end support and the leaf spring are designed respectively, so that the actual stiffness of the leaf spring is consistent with the theoretical stiffness obtained in S2; after point a and point c are determined, the structure of the leaf spring can be designed in detail. The detailed design of the leaf spring structure is mainly to design the cross-sectional dimensions of the leaf spring based on the theoretical stiffness of the leaf spring obtained in S2, so that the actual stiffness of the designed leaf spring is consistent with the theoretical stiffness. In addition, in order to prevent the leaf spring from breaking in extreme or accidental situations, resulting in uncontrollable vehicle, the front section of the leaf spring is generally designed to be two pieces.

[0048] S9: Design the leaf spring upper cover according to the coordinates of point b; design the leaf spring upper cover in detail in combination with the airbag pressure, shock absorber recovery and compression resistance. The leaf spring upper cover integrates the leaf spring cover, airbag lower support and shock absorber lower support, so comprehensive loading is required during analysis.

[0049] S10: Based on the structure designed in S8 and S9, a CAE analysis model is established to check whether the strength of the structure meets the requirements. After the structure of the composite front air suspension is determined, a final strength analysis is required. The working conditions analyzed are mainly bending conditions, emergency braking, emergency steering and single-side wheel lifting conditions.

[0050] The present invention first calculates the composite stiffness of the front suspension, and then calculates the theoretical stiffness of the leaf spring after the airbag is selected, and then gradually determines the coordinates of the center point of the connection between the leaf spring and the fixed end support, the fixed center point of the airbag and the leaf spring upper cover plate, and the center point of the connection between the leaf spring and the ear end support, and then respectively designs the structures of the leaf spring upper cover plate, the fixed end support, the ear end support and the leaf spring, so that the actual stiffness of the leaf spring is consistent with the calculated theoretical stiffness, and finally checks the strength of the structure of the entire front suspension; since the Y-axis coordinate of the fixed center point of the airbag and the leaf spring upper cover plate is the optimal value obtained by establishing a nonlinear CAE analysis model of the front suspension, and the Z-axis coordinate of the center point of the connection between the leaf spring and the fixed end support and the center point of the connection between the leaf spring and the ear end support are the optimal values ​​obtained by establishing a front suspension dynamics analysis model, the front suspension designed by the present invention has reasonable installation positions of the leaf spring and the airbag, and the leaf spring has the least influence on the steering wheel during movement.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for optimizing the design of a composite front air suspension, the composite front air suspension comprising a vehicle frame, a front axle, a leaf spring, an airbag and a leaf spring upper cover, the vehicle frame being fixedly connected with a fixed end support and a lifting eye end support, one end of the leaf spring being hinged to the fixed end support, the other end of the leaf spring being hinged to the lifting eye end support, the leaf spring being mounted on the front axle, the leaf spring upper cover being arranged on the leaf spring, the airbag being mounted on the leaf spring upper cover, the center point of the leaf spring being connected to the fixed end support being point a, the fixed center point of the airbag and the leaf spring upper cover being point b, the center point of the leaf spring being connected to the lifting eye end support being point c, and characterized in that: The following steps are involved: S1: Calculate the composite stiffness of the front suspension based on the front axle sprung mass and the front suspension system frequency; S2: After the airbag is selected, the composite stiffness of the front suspension obtained in S1 is subtracted from the stiffness of the airbag under standard load to obtain the theoretical stiffness of the leaf spring; S3: Establish a rectangular coordinate system with the center point of the front axle of the vehicle as the zero point, wherein the length direction of the vehicle is the X-axis direction, the width direction of the vehicle is the Y-axis direction, and the height direction of the vehicle is the Z-axis direction; S4: Determine the X-axis coordinate of point a as x according to the length of the leaf spring a And determine the X-axis coordinate of point c as x c According to the width of the front axle and the rotation envelope of the front wheel, the Y-axis coordinate of point a is determined as y a And determine the Y-axis coordinate of point c as y c , according to the height of the front axle from the ground, the Z-axis coordinate of point b is determined as z b ; S5: According to the layout of the engine and the rotation envelope of the front wheel, the Y-axis coordinate of point b is determined as y b and determine the layout range of the X-axis coordinate of point b; S6: According to the determined x a 、x c ,y a ,y c 、z b and b , a nonlinear CAE analysis model of the front suspension including the airbag and the leaf spring of the initial structure is established, the X-axis coordinate of point b is set as a variable, and the X-axis coordinate of point b is determined as x according to the optimal stress results of the leaf spring obtained when the front suspension is in bending condition and emergency braking condition. b ; S7: According to the determined, x a 、x c ,y a ,y c 、z b ,y b and x b , establish a front suspension dynamics analysis model including airbags, leaf springs and steering systems, set the Z-axis coordinates of point a and point c as variables, and determine the Z-axis coordinate of point a as z according to the optimal interference result of the front suspension and steering system during motion. a And determine the Z-axis coordinate of point c as z c ; S8: According to the coordinates of point a and point c, the structures of the fixed end support, the eye end support and the leaf spring are designed respectively, so that the actual stiffness of the leaf spring is consistent with the theoretical stiffness obtained in S2; S9: Design the upper cover of the leaf spring according to the coordinates of point b; S10: Based on the structure designed in S8 and S9, a CAE analysis model is established to check whether the strength of the structure meets the requirements.

2. The composite front air suspension optimization design method according to claim 1, characterized in that: In S1, according to the formula Calculate the composite stiffness of the front suspension, where n is the suspension system frequency, C is the suspension stiffness, and M is the sprung mass.

3. The composite front air suspension optimization design method according to claim 1, characterized in that: In S2, the type of the airbag is determined according to the height and load-bearing mass of the airbag.

4. The composite front air suspension optimization design method according to claim 1, characterized in that: In S6, the optimal stress result of the leaf spring is: in the bending condition, the stress of the leaf spring is the minimum, and in the emergency braking condition, the stress of the leaf spring is less than 90% of the yield strength of the leaf spring.

5. The composite front air suspension optimization design method according to claim 1, characterized in that: In the S7, the optimal interference result between the front suspension and the steering system during movement is that the leaf spring causes the steering wheel to deflect at the minimum angle during movement.

6. The composite front air suspension optimization design method according to claim 1, characterized in that: In S7, the Z-axis coordinate of point a is the same as the Z-axis coordinate of point c.

7. The composite front air suspension optimization design method according to claim 1, characterized in that: In the S8, the front end of the leaf spring is designed as two leaves.

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