A method for designing air suspension stiffness

Abstract

The air suspension stiffness design method provided by the present invention includes the following steps: designing the maximum stroke of the air suspension; designing the height modes of the air suspension, the corresponding heights between the height modes, and the use positioning of each height mode; designing the expected performance indicators corresponding to each height mode and the relationship between the performance indicators based on the use positioning of each height mode; determining the air suspension stiffness under different loads and different heights, and the relationship between the air suspension stiffness under different loads and different heights based on the performance indicators corresponding to each height mode and the relationship between the performance indicators; confirming the form of the expected air suspension stiffness curve; fitting the air suspension stiffness curve; analyzing the fitted air suspension stiffness curve, and if the air suspension that meets the curve does not have the expected performance indicators, re-determining the air suspension stiffness under different loads and different heights, and the relationship between the air suspension stiffness under different loads and different heights.

Description

Technical Field

[0001] The present invention relates to the field of vehicle suspension design, and in particular to a method for designing air suspension stiffness. Background Art

[0002] Air suspension refers to a suspension system with air springs added to it, capable of adjusting its height and firmness according to road conditions. During vehicle suspension design, the ride and handling stability of an air suspension are performance objectives that must be considered. These are largely determined by corresponding performance indicators, which are intuitively reflected in their numerical values. Stiffness (i.e., the force required per unit displacement of the structure) directly impacts the vehicle's performance. Specifically, performance indicators corresponding to ride comfort typically include first-order comfort and second-order comfort. Performance indicators corresponding to handling stability typically include roll gradient and maximum braking pitch angle. First-order comfort refers to first-order body motion control, encompassing pitch, roll, and heave (typically 0-5Hz). Second-order comfort refers to the driver's perceived or observed vibration and jerkiness of the vehicle's body, frame, and suspension, as well as the roughness caused by road texture or irregularities. The roll gradient represents the vehicle's roll angle per unit lateral acceleration, while the maximum braking pitch angle represents the vehicle's maximum pitch angle during braking.

[0003] In other words, the stiffness design of the air suspension directly affects the ride comfort and handling stability of the vehicle. However, currently, no design method has been published that directly incorporates the performance indicators corresponding to these two performance objectives into the design process during the early stages of the air suspension stiffness design. The following two main air suspension stiffness design methods are commonly used:

[0004] 1. Bottom-up design: First, based on the vehicle's positioning requirements and body model, and referring to the K&C (kinematics and compliance) test of a benchmark vehicle, a rough definition of the air suspension stiffness versus wheel hop curve is defined. The air spring is then designed based on this curve, and the air spring is incorporated into the entire suspension for overall simulation analysis. Finally, chassis tuning is performed. During this step, the air suspension is adjusted to meet performance indicators to determine the final suspension stiffness. The main drawback of this design method is the need for costly K&C testing of benchmark vehicles. Furthermore, it cannot directly address performance objectives during the early design process. The two performance objectives of ride quality and handling stability must be achieved through chassis tuning. This design method places high demands on the designer's own professional expertise and design experience, and is not conducive to shortening the project development cycle or improving development efficiency.

[0005] 2. The stiffness design of another type of air suspension is primarily based on the results of two aspects: offset frequency and K&C tests on a benchmark vehicle. The specific steps include: based on the vehicle body model, the offset frequency (i.e., the resonant frequency of a mass in the vehicle mass system when it vibrates) is used to reversely calculate the suspension stiffness of the air suspension to be designed at a certain height and load. Combined with bench testing, the stiffness curve of the benchmark vehicle's air suspension is then derived, roughly defining the curve of the stiffness of the air suspension to be designed with wheel hop. Finally, the performance indicators corresponding to the performance targets are introduced into the chassis tuning stage to determine the final suspension stiffness.

[0006] The disadvantage of this design method is that the stiffness of the air spring in the air suspension is nonlinear. The above-mentioned off-frequency inverse calculation method can only correspond to the stiffness of the air suspension to be designed at a specific load and a specific height, which is not representative. In addition, the curve of the stiffness of the air suspension to be designed, which is derived by combining this stiffness with the stiffness curve of the benchmark vehicle, is largely imitated from the reference benchmark vehicle. It cannot perfectly combine with the actual body conditions of the vehicle to be designed and directly take into account both smoothness and handling stability in one step. Therefore, after obtaining the curve of the stiffness of the air suspension to be designed with wheel hop based on the off-frequency inverse calculation results and the K&C test of the reference benchmark vehicle, it is still necessary to rely on the experience of the designer and conduct heavy chassis adjustment work to determine the final suspension stiffness.

[0007] As can be seen from the above, the current design of air suspension stiffness requires K&C testing of benchmark vehicles. There is no means to reduce the workload of the chassis adjustment stage through theoretical calculations in the early design stage. Air suspension-related performance indicators (such as smoothness and handling stability) are not taken into consideration in the early design stage. At the same time, there is no public design method that can first obtain the overall stiffness curve of the air suspension and then design the stiffness of each component in the suspension system (such as air springs). Summary of the Invention

[0008] In view of this, an object of the present invention is to provide an air suspension stiffness design method, which can directly obtain the overall stiffness curve of the air suspension to be designed without the need for a benchmark vehicle K&C test.

[0009] The present invention provides an air suspension stiffness design method, comprising the following steps:

[0010] Design the air suspension's maximum travel;

[0011] Design the height modes of the air suspension, the corresponding heights between each height mode, and the usage positioning of each height mode;

[0012] Based on the usage positioning of each height mode, design the expected performance indicators corresponding to each height mode and the relationship between each performance indicator;

[0013] Determine the stiffness of the air suspension under different loads and heights, and the relationship between the stiffness of the air suspension under different loads and heights, based on the performance indicators corresponding to each height mode and the relationship between the performance indicators;

[0014] Confirm the expected air suspension stiffness curve form;

[0015] Taking several air suspension stiffnesses as key design points, fitting the air suspension stiffness curve based on the key design points and the expected air suspension stiffness curve form;

[0016] The air suspension stiffness curve obtained by the fitting is analyzed. If the air suspension that meets the curve does not have the expected performance indicators, the air suspension stiffness under different loads and different heights, as well as the relationship between the air suspension stiffness under different loads and different heights, are re-determined until the air suspension has the expected performance indicators.

[0017] Optionally, the performance indicator can represent a performance target, the performance target including ride comfort and handling stability, and the step of designing height modes of the air suspension, corresponding heights between each height mode, and usage positioning of each height mode includes: designing the height modes to include a sport mode, a comfort mode, and an off-road mode, the corresponding height of the air suspension in the sport mode being smaller than the corresponding height in the comfort mode, and the corresponding height of the air suspension in the comfort mode being smaller than the corresponding height in the off-road mode;

[0018] The handling stability of the sport mode is higher than that of the comfort mode and off-road mode, and its smoothness is lower than that of the off-road mode and comfort mode. The handling stability of the comfort mode is higher than that of the off-road mode, and its smoothness is higher than that of the sport mode and off-road mode.

[0019] Optionally, the performance indicators corresponding to the ride comfort include first-order comfort and second-order comfort, and the performance indicators corresponding to the handling stability include roll gradient and maximum braking head angle. The design values ​​of the roll gradient and maximum braking head angle of the sport mode are smaller than those of the comfort mode and the off-road mode, and the design values ​​of the first-order comfort and second-order comfort are larger than those of the off-road mode and the comfort mode. The design values ​​of the roll gradient and maximum braking head angle of the comfort mode are smaller than those of the off-road mode, and the design values ​​of the first-order comfort and second-order comfort are smaller than those of the sport mode and the off-road mode.

[0020] In comfort mode, the difference in roll gradient between one person and fully loaded conditions is less than the preset threshold.

[0021] Optionally, the step of determining the stiffness of the air suspension at different loads and different heights, and the relationship between the stiffness of the air suspension at different loads and different heights comprises:

[0022] The corresponding suspension stiffness is calculated inversely according to the frequency deviation calculation formula;

[0023] The stiffness of the air suspension corresponding to the height in the off-road mode under the same load is greater than the stiffness corresponding to the height in the comfort mode, and less than the stiffness corresponding to the height in the sports mode.

[0024] Optionally, K 3半 =1.5K 4半 , K 5半 =1.2K 4半 , where K 3半 is the suspension stiffness of the air suspension in the sport mode at half load, K 4半 is the suspension stiffness of the air suspension in comfort mode at half load, K 5半 It is the suspension stiffness of the air suspension in off-road mode with half load.

[0025] Optionally, the step of confirming the expected air suspension stiffness curve form includes: confirming that the expected air suspension stiffness curve form is an inverted S-shape.

[0026] Optionally, the step of fitting the air suspension stiffness curve using several air suspension stiffnesses as key design points and the key design points and the expected air suspension stiffness curve form as a fitting basis includes:

[0027] The stiffness of the air suspension at the upper jump limit position, the stiffness at the lower jump limit position, the corresponding stiffness when in sports mode, the corresponding stiffness when in comfort mode, and the corresponding stiffness when in off-road mode are selected as key design points.

[0028] Optionally, the step of fitting the air suspension stiffness curve with several air suspension stiffnesses as key design points and the key design points and the expected air suspension stiffness curve form as the fitting basis includes: establishing a two-dimensional matrix of air suspension stiffness according to the several key design points, the two-dimensional matrix including a load dimension and a height dimension, in the load dimension, the air suspension height includes at least the height corresponding to the sports mode, the height corresponding to the comfort mode and the height corresponding to the off-road mode, in the height dimension, the air suspension load includes at least no load, half load and full load.

[0029] Optionally, the step of re-determining the air suspension stiffness at different loads and different heights, and the relationship between the air suspension stiffness at different loads and different heights, includes re-determining the air suspension stiffness at different loads and different heights, and the relationship between the air suspension stiffness at different loads and different heights, by at least one of the following methods:

[0030] Adjust the offset frequency, or

[0031] Adjust the relationship between the stiffness of the air suspension at different heights.

[0032] Optionally, the expected air suspension stiffness curve includes a nearly linear segment, and the step of fitting the air suspension stiffness curve based on the key design points and the expected air suspension stiffness curve further includes:

[0033] The air suspension stiffness corresponding to the first and last ends of the linear segment is reversed to serve as the iterative value for adjusting the air suspension stiffness curve.

[0034] In summary, by incorporating performance objectives into the early stages of air suspension stiffness design, the present invention enables the design of the air suspension stiffness curve to be conducted while ensuring that the performance objectives are generally in line with expectations. This improves the accuracy of the air suspension stiffness curve design and reduces the workload of the overall air suspension design and development. More specifically, the present invention has the following beneficial effects:

[0035] 1. A top-down air suspension stiffness design method, which has not yet been made public, is proposed to directly design the overall stiffness of the air suspension. Using this method, key design points can be used as the basis for fitting during the design process to reversely propose design requirements for the suspension stiffness curve (for example, making the stiffness curve an inverted S-shape) and the design requirements for the air spring, which can shorten the workload of the air spring design and adjustment steps.

[0036] 2. Using performance indicators as the design basis to construct key design points for fitting the air suspension stiffness curve introduces performance target considerations into the early design phase of the air suspension. This allows for the definition of a full-stroke stiffness curve with two-dimensional matrix characteristics in the early design phase, improving early design accuracy, reducing the workload of later design iterations or repeated adjustments, and increasing vehicle tuning efficiency, saving development costs.

[0037] 3. The approach of fitting the air suspension stiffness curve using the corresponding air suspension stiffness under different load and height modes as key design points is not only more comprehensive and accurate (using multiple key design points) but also eliminates the costly benchmarking test steps, taking into account both economy and accuracy.

[0038] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the air suspension stiffness curve provided by an embodiment of the present invention.

[0040] Description of Reference Numerals

[0041] I - Nearly linear segment. DETAILED DESCRIPTION

[0042] The following embodiments of the present invention are described in further detail with reference to 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.

[0043] The air suspension stiffness design method described in the present invention is as follows: in the early design stage, the performance indicators corresponding to each performance target and the commonly used heights of the air suspension are determined, so that the relationship between the stiffness corresponding to each height under different loads depends on each performance indicator, so as to introduce consideration of the performance target, and then construct the stiffness curve of the air suspension with the stiffness of the air suspension under specific conditions as the key design point. Then, simulation is performed based on the obtained stiffness curve, and the performance indicators obtained by the simulation model are compared and analyzed with the performance indicators corresponding to the expected performance targets. According to the difference between the two, the relevant parameters of the air suspension are adjusted until the simulation model has the performance indicators corresponding to the expected performance targets.

[0044] Specifically, the air suspension stiffness design method provided in this embodiment includes the following steps:

[0045] S1: Determine the maximum travel of the air suspension based on market demand and vehicle positioning.

[0046] S2: Design the height modes of the air suspension, the heights corresponding to each height mode, and the usage positioning of each height mode; specifically, confirm the height modes of the air suspension, the vehicle heights corresponding to each height mode, and the usage positioning of each height mode based on market demand and vehicle model positioning, and confirm the tendency of each height mode for different performance goals based on the usage positioning of each height mode of the air suspension during driving.

[0047] In this embodiment, the air suspension's performance objectives include ride comfort and handling stability. Three height modes are provided: Sport, Comfort, and Off-Road. The corresponding vehicle heights for these three modes are arranged in ascending order: Sport < Comfort < Off-Road. That is, in Sport mode, the vehicle's center of mass is lowest, followed by Comfort, and highest in Off-Road. Of the three height modes, Sport mode is designed to offer the best handling stability and the worst ride comfort, enhancing driving enjoyment for the driver. Comfort mode is designed to offer handling stability greater than Off-Road but less than Sport, with the best ride comfort and minimal variation in handling stability under varying loads, providing the most comfortable driving environment for the driver. Off-Road mode is designed to provide high maneuverability (i.e., a high center of mass) to facilitate handling over bumpy or rugged roads. This mode requires the lowest handling stability, but higher than Sport and lower than Comfort for ride comfort.

[0048] S3: Based on the usage positioning of each altitude mode, design the expected performance indicators corresponding to each altitude mode and the relationship between each performance indicator; specifically, based on the performance goals, confirm the relationship between the performance indicators corresponding to each altitude mode, and determine the preferred values ​​of these performance indicators based on the vehicle positioning.

[0049] In this embodiment, the performance indicators corresponding to ride comfort include first-order comfort and second-order comfort, and the performance indicators corresponding to handling stability include roll gradient and maximum braking head angle. Furthermore, the performance indicator corresponding to minimal differences in handling stability under different loads in comfort mode includes the difference in vehicle roll gradient between one person (based on 100 kg) and fully loaded conditions being less than a preset threshold (e.g., 0.1° / g, where g is the acceleration due to gravity). Since smaller design values ​​for first-order comfort, second-order comfort, roll gradient, and maximum braking head angle indicate better vehicle performance on that performance indicator, in this embodiment, the relationship between the design values ​​for first-order comfort, second-order comfort, roll gradient, and maximum braking head angle for Sport, Comfort, and Off-Road modes is as follows:

[0050]

[0051]

[0052] It should be noted that the present embodiment does not list the specific design values ​​corresponding to the first-order comfort, second-order comfort, roll gradient and maximum braking point head angle, because these can be determined by those skilled in the art as needed in combination with the specific parameters of the air suspension to be designed, which has great flexibility. Failure to describe this in detail will not affect the sufficiency of the disclosure of this embodiment.

[0053] S4: determining the stiffness of the air suspension under different loads and different heights, and the relationship between the stiffness of the air suspension under different loads and different heights, based on the performance indicators corresponding to the various height modes and the relationship between the performance indicators;

[0054] Specifically, the frequency offsets for comfort mode in the no-load, half-load, and full-load states are set based on the front and rear axle weights (i.e., the vehicle's axle load parameters) when the vehicle is unloaded, half-loaded, and fully loaded. The corresponding suspension stiffnesses for comfort mode in the no-load, half-load, and full-load states are then calculated using the frequency offset calculation formula. Specifically, the suspension stiffness calculation formula is K = [(2*π*f)^2]*M, where K is the suspension stiffness, f is the frequency offset, and M is the sprung mass. K, f, and M are different under different loads.

[0055] Several design points are selected according to the air suspension's maximum travel and the air suspension's height mode. In this embodiment, a total of five design points are selected, among which the stiffness of the air suspension at the upper jump limit position is K1, the stiffness of the air suspension at the lower jump limit position is K2, the suspension stiffness when the air suspension is in the sports mode at the corresponding height is K3, the suspension stiffness when the air suspension is in the comfort mode at the corresponding height is K4, and the suspension stiffness when the air suspension is in the off-road mode at the corresponding height is K5.

[0056] Based on the suspension stiffness K4 in Comfort mode at no-load, half-load, and full-load states, and combined with the expected performance indicators set in S3, the suspension stiffness K3 in Sport mode under different loads and the suspension stiffness K5 in Off-Road mode under different loads are set. K3, K5, and K4 have different values ​​in different situations. This allows designers to obtain multiple suspension stiffness data points corresponding to each load and height mode. These suspension stiffnesses that meet the expected performance indicators serve as key design points for subsequent fitting of the suspension stiffness curve, allowing the air suspension stiffness curve to directly take into account performance objectives during its design phase.

[0057] A more detailed description is that under the same load (i.e., no load, half load, or full load), K3, K5, and K4 always satisfy the rule of K3>K5>K4. Of course, the multiple relationship between these three can be flexibly set by those skilled in the art according to actual conditions. For example, the suspension stiffness in the comfort mode at half load is recorded as K 4半 , the suspension stiffness of the air suspension in the sport mode at half load is recorded as K 3半 , the suspension stiffness of the air suspension in off-road mode at half load is recorded as K 5半 In this embodiment, K 3半 =1.5K 4半 , K 5半 =1.2K 4半 In addition, for the convenience of description, the following reference to the suspension stiffness in the comfort mode under no-load conditions will be expressed in K.4空 Indicates that the suspension stiffness in the sport mode under no-load conditions will be expressed in K 3空 It is said that when referring to the suspension stiffness in off-road mode under no-load conditions, K 5空 It is said that the suspension stiffness in comfort mode under full load will be expressed in K 4满 It is said that the suspension stiffness in the sport mode under full load will be expressed in K 3满 It is said that when referring to the suspension stiffness in off-road mode under full load, it will be expressed in K 5满 express.

[0058] In addition, in this embodiment, it is also necessary to set the forces on the air suspension at the upper and lower limit positions; specifically, the forces on the air suspension at the lower limit position (i.e., the forces on the suspension wheel center) are set to 0 (this is common knowledge in the art and will not be elaborated on), and the forces on the air suspension at the upper limit position are set to 3.5 times the full load weight of the vehicle; on the premise that the forces at the upper and lower limit positions are clear, the corresponding stiffnesses of the air suspension at the upper and lower limit positions when in different load states can be obtained (the conversion here is common knowledge in the art and will not be elaborated on); in addition, for the convenience of expression, the corresponding stiffnesses of the air suspension at the upper limit position when empty, half-loaded, and fully loaded are respectively recorded as K 1空 , K 1半 and K 1满 The corresponding stiffness of the air suspension at the lower limit position when it is empty, half loaded and fully loaded is recorded as K 2空 , K 2半 and K 2满 .

[0059] S5: Confirm the expected air suspension stiffness curve form; since the basic stiffness characteristics of the air spring can be designed into an ideal reverse "S" form as needed, the stiffness characteristics of the air spring are close to linear within the normal driving deflection range, and become nonlinear when the normal driving deflection range is exceeded. This reverse S-shaped characteristic curve is beneficial for preventing excessive travel when the suspension moves beyond the normal driving deflection range. Therefore, in this embodiment, the air suspension stiffness curve is set as follows: Figure 1 As shown in the reverse "S" shape, in this way, within the normal driving deflection range, the stiffness curve of the air suspension is close to linear (such as Figure 1The benefits of this design include, in addition to preventing the suspension from moving excessively when performing movements beyond the normal driving deflection range, maintaining almost constant frequency offset when the load on the air suspension changes (i.e., when the stiffness curve is approximately linear, K = [(2*π*f)^2]*M, K and M have the same changing trend, and f can be a nearly constant quantity). This helps reduce factors that can cause changes in body amplitude during the vehicle design process.

[0060] S6: Taking several air suspension stiffnesses as key design points, fitting the air suspension stiffness curve based on the key design points and the expected air suspension stiffness curve form; specifically, according to the parameters confirmed in S4-S5, taking the air suspension stiffnesses corresponding to each height mode under each load, and the stiffnesses of the air suspension at the upper jump limit position and the lower jump limit position under different load states as key design points, create a two-dimensional matrix of air suspension stiffness, the two-dimensional matrix includes load dimension and height dimension, taking each air suspension stiffness data point obtained in the load dimension and height dimension as key design points, construct the air suspension stiffness curve. Stiffness curve corresponding to the full stroke of the suspension; it should be noted that, in this embodiment, in the load dimension, the air suspension height includes at least the height corresponding to the sports mode, the height corresponding to the comfort mode and the height corresponding to the off-road mode. When listing the elements of the two-dimensional matrix in the load dimension, the air suspension height is used as the quantitative value, and the corresponding full-stroke stiffness curves under different load states are listed. In the height dimension, the air suspension load includes at least no load, half load and full load. When listing the elements of the two-dimensional matrix in the height dimension, the load is used as the quantitative value, and the corresponding full-stroke stiffness curves under different height states are listed.

[0061] For the above steps, the stiffness curve corresponding to the full stroke of the air suspension can be constructed by taking the air suspension stiffness data points obtained in the load dimension and the height dimension as the key design points; for example, in the load dimension, when the height is the height corresponding to the sports mode, at least K 1空 , K 1半 , K 1满 , K 2空 , K 2半 , K 2满 , K 3空 , K 3半 and K 3满 As the key design point, theoretical calculation or simulation can be used to obtain the corresponding force of the full stroke of the air suspension under different loads when the air suspension is in the corresponding height of the sports mode. Then, based on the expected design of making the air suspension stiffness curve in an inverted S shape, the key design points can be selected and the curve fitting can be performed to finally obtain the following: Figure 1 The inverse S-shaped stiffness curve is shown.

[0062] A more detailed description is that when the height of the air suspension is the height corresponding to the sports mode, and the air suspension is in an unloaded state, K 1空 and K 2空 Determine the first and last points of the stiffness curve, that is, the stiffness of the motion mode at the upper and lower limit positions, and then determine K 3空 Since the stiffness curve is known to be an inverse S-shaped curve and is close to linear within the normal driving deflection range, a preliminary fitting can be obtained according to the design requirements. Figure 1 The stiffness curve is shown as an inverse S shape, and reverse calculation can be obtained Figure 1 The air suspension stiffness values ​​corresponding to the first and last endpoints of the near-linear segment I can be used as iterative values ​​for subsequent air suspension stiffness curve adjustment iterations. Of course, on the stiffness curve, between the upper and lower jump limit positions, multiple air suspension stiffness values ​​obtained by preliminary fitting can also be obtained in this way to serve as initial values ​​for subsequent adjustment iterations.

[0063] In this way, the key design points are used as the fitting basis to fit the obtained results, and the full-stroke air suspension stiffness curve corresponding to different loads in the sports mode can be obtained. Similarly, when the height of the air suspension is the height corresponding to the comfort mode, the K 1空 , K 1半 , K 1满 , K 2空 , K 2半 , K 2满 , K 4空 , K 4半 , K 4满 As the key design point, the full-stroke air suspension stiffness curve corresponding to different loads in comfort mode can be obtained. When the height of the air suspension is in off-road mode, K 1空 , K 1半 , K 1满 , K 2空 , K 2半 , K 2满 , K 5空 , K 5半 and K 5满 As the key design point, the full-stroke air suspension stiffness curve corresponding to different loads in off-road mode can be obtained.

[0064] Based on the above, in the height dimension, when the air suspension load is empty, the suspension height is changed to K 1空 , K 2空 , K 3空 , K 4空 , K 5空As the key design point, and with the key design point as the fitting basis, the full-stroke air suspension stiffness curve corresponding to different suspension heights when no-load is obtained by fitting using theoretical calculation or simulation. 1半 , K 2半 , K 3半 , K 4半 , K 5半 As the key design point, the full-stroke air suspension stiffness curve corresponding to different suspension heights at half load can be obtained; 1满 , K 2满 , K 3满 , K 4满 , K 5满 By using the key design points as the key design points, the full-stroke air suspension stiffness curve corresponding to different suspension heights at full load can be obtained. Of course, in addition to the aforementioned key design points, those skilled in the art can also calculate the air suspension stiffness under different conditions as needed, and use the calculated air suspension stiffness under different conditions as the key design points to participate in fitting the stiffness curve. During the fitting process, those skilled in the art can adopt a fitting method in which the fitting curve must pass through the key design points, or a fitting method in which the fitting curve does not necessarily pass through the key design points. In addition, the purpose of creating a two-dimensional matrix is ​​to facilitate designers to more efficiently draw the air suspension stiffness curve and facilitate data viewing and modification. In possible embodiments, under the premise of knowing the key design points, it is also possible to not create a two-dimensional matrix and directly fit the air suspension stiffness curve based on the key design points.

[0065] S7: Analyze the air suspension stiffness curve obtained by fitting. If the air suspension that meets the curve does not meet the expected performance indicators, re-determine the air suspension stiffness under different loads and different heights, as well as the relationship between the air suspension stiffness under different loads and different heights, until the air suspension meets the expected performance indicators. Specifically, based on relevant parameters (such as the half-load axle load, center of mass position, and moment of inertia of the vehicle), establish an air suspension simulation model with the stiffness curve described in step S6, and analyze the performance indicators. If the performance indicator obtained by analysis is equal to or less than the expected performance indicator set in step S3, it means that the air suspension has met the expected performance target. Otherwise, repeat steps S4 to this step, and in step S4, reset the offset frequency value or reset the multiple relationship between the stiffness under different loads in the sport mode, off-road mode, and comfort mode (both of which can be adjusted) to obtain new key design points different from the original key design points, until an air suspension that meets the expected performance target is obtained in this step. In this embodiment, the simulated vehicle model is constructed and analyzed in ADAMS (Automated Dynamics Analysis Software for Mechanical Systems).

[0066] S8: Perform chassis adjustment based on the air suspension parameters obtained in step S7.

[0067] In summary, by incorporating performance objectives into the early stages of air suspension stiffness design, the present invention enables the design of the air suspension stiffness curve to be conducted while ensuring that the performance objectives are generally in line with expectations. This improves the accuracy of the air suspension stiffness curve design and reduces the workload of the overall air suspension design and development. More specifically, the present invention has the following beneficial effects:

[0068] 1. A top-down air suspension stiffness design method, which has not yet been made public, is proposed to directly design the overall stiffness of the air suspension. Using this method, key design points can be used as the basis for fitting during the design process to reversely propose design requirements for the suspension stiffness curve (for example, making the stiffness curve an inverted S-shape) and the design requirements for the air spring, which can shorten the workload of the air spring design and adjustment steps.

[0069] 2. Using performance indicators as the design basis to construct key design points for fitting the air suspension stiffness curve introduces performance target considerations into the early design phase of the air suspension. This allows for the definition of a full-stroke stiffness curve with two-dimensional matrix characteristics in the early design phase, improving early design accuracy, reducing the workload of later design iterations or repeated adjustments, and increasing vehicle tuning efficiency, saving development costs.

[0070] 3. The approach of fitting the air suspension stiffness curve using the corresponding air suspension stiffness under different load and height modes as key design points is not only more comprehensive and accurate (using multiple key design points) but also eliminates the costly benchmarking test steps, taking into account both economy and accuracy.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for designing air suspension stiffness, characterized in that: The following steps are involved: Design the air suspension's maximum travel; Design the height modes of the air suspension, the corresponding air suspension heights for each height mode, and the usage positioning of each height mode; Based on the usage positioning of each height mode, design the expected performance indicators corresponding to each height mode and the relationship between each performance indicator; The air suspension stiffness under different loads and different heights, as well as the relationship between the air suspension stiffness under different loads and different heights, is determined based on performance indicators corresponding to each height mode and the relationship between the performance indicators. The performance indicators can represent performance targets, and the performance targets include ride comfort and handling stability. The steps of designing the height modes of the air suspension, the air suspension heights corresponding to each height mode, and the usage positioning of each height mode include: designing the height modes to include a sport mode, a comfort mode, and an off-road mode, the corresponding height of the air suspension in the sport mode being less than the corresponding height in the comfort mode, and the corresponding height of the air suspension in the comfort mode being less than the corresponding height in the off-road mode; and the steps of determining the air suspension stiffness under different loads and different heights, as well as the relationship between the air suspension stiffness under different loads and different heights include: The corresponding suspension stiffness is calculated inversely according to the frequency deviation calculation formula; The stiffness of the air suspension in off-road mode under the same load is greater than that in comfort mode and less than that in sport mode. Confirm the expected air suspension stiffness curve form; Taking several air suspension stiffnesses as key design points, fitting the air suspension stiffness curve based on the key design points and the expected air suspension stiffness curve form; The air suspension stiffness curve obtained by the fitting is analyzed. If the air suspension that meets the curve does not have the expected performance indicators, the air suspension stiffness under different loads and different heights, as well as the relationship between the air suspension stiffness under different loads and different heights, are re-determined until the air suspension has the expected performance indicators.

2. The air suspension stiffness design method according to claim 1, wherein: The handling stability of the sport mode is higher than that of the comfort mode and off-road mode, and its smoothness is lower than that of the off-road mode and comfort mode. The handling stability of the comfort mode is higher than that of the off-road mode, and its smoothness is higher than that of the sport mode and off-road mode.

3. The air suspension stiffness design method according to claim 2, wherein: The performance indicators corresponding to the ride comfort include first-order comfort and second-order comfort. The performance indicators corresponding to the handling stability include roll gradient and maximum braking head angle. The design values ​​of the roll gradient and maximum braking head angle of the Sport mode are smaller than those of the Comfort mode and the Off-road mode, and the design values ​​of the first-order comfort and second-order comfort are larger than those of the Off-road mode and the Comfort mode. The design values ​​of the roll gradient and maximum braking head angle of the Comfort mode are smaller than those of the Off-road mode, and the design values ​​of the first-order comfort and second-order comfort are smaller than those of the Sport mode and the Off-road mode. In comfort mode, the difference in roll gradient between one person and fully loaded conditions is less than the preset threshold.

4. The air suspension stiffness design method according to claim 1, wherein: K 3半 =1.5K 4半 , K 5半 =1.2K 4半 , where K 3半 is the suspension stiffness of the air suspension in the sport mode at half load, K 4半 is the suspension stiffness of the air suspension in comfort mode at half load, K 5半 It is the suspension stiffness of the air suspension in off-road mode with half load.

5. The air suspension stiffness design method according to claim 1, wherein: The step of confirming the expected air suspension stiffness curve form includes confirming that the expected air suspension stiffness curve form is an inverted S-shape.

6. The air suspension stiffness design method according to claim 3, wherein: The steps of fitting the air suspension stiffness curve using several air suspension stiffnesses as key design points and the expected air suspension stiffness curve form as the fitting basis include: The stiffness of the air suspension at the upper jump limit position, the stiffness at the lower jump limit position, the corresponding stiffness when in sports mode, the corresponding stiffness when in comfort mode, and the corresponding stiffness when in off-road mode are selected as key design points.

7. The air suspension stiffness design method according to claim 3, wherein: The step of fitting an air suspension stiffness curve with several air suspension stiffnesses as key design points and the key design points and the expected air suspension stiffness curve form as the fitting basis includes: establishing a two-dimensional matrix of air suspension stiffness according to the several key design points, the two-dimensional matrix including a load dimension and a height dimension. In the load dimension, the air suspension height includes at least a height corresponding to a sport mode, a height corresponding to a comfort mode, and a height corresponding to an off-road mode. In the height dimension, the air suspension load includes at least no load, half load, and full load.

8. The air suspension stiffness design method according to claim 1, wherein: The step of re-determining the air suspension stiffness at different loads and different heights, and the relationship between the air suspension stiffness at different loads and different heights, comprises: re-determining the air suspension stiffness at different loads and different heights, and the relationship between the air suspension stiffness at different loads and different heights, by at least one of the following methods: Adjust the offset frequency, or Adjust the relationship between the stiffness of the air suspension at different heights.

9. The air suspension stiffness design method according to claim 5, wherein: The expected air suspension stiffness curve includes a nearly linear segment. The steps of fitting the air suspension stiffness curve based on the key design points and the expected air suspension stiffness curve form further include: The air suspension stiffness corresponding to the first and last ends of the linear segment is reversed to serve as the iterative value for adjusting the air suspension stiffness curve.

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