Determination method of vehicle dynamic limit load coefficient based on suspension system

Abstract

The present invention relates to the field of automobile testing technology, and relates to a method for determining a dynamic limit load coefficient of a vehicle based on a suspension system. The method comprises the following steps: modifying a vehicle to a set degree so that wheel friction marks are displayed when the vehicle is dynamically tested under extreme road conditions, marking corresponding modified areas, and obtaining the marked marks of the vehicle after the dynamic test under extreme road conditions; visualizing the marked marks of the vehicle, and processing the vehicle to a set degree so that the tires of the vehicle are in contact with the marked marks of the vehicle, and the relative geometric trajectories of the tires and the vehicle remain consistent, and measuring to obtain a static measurement value; calculating the static measurement value through a suspension disturbance comparison algorithm to obtain a buffer block compression amount and a spring compression amount, combining the buffer block compression amount and the spring compression amount, and performing reverse calculation through a first setting formula, a second setting formula, and a third setting formula to obtain the vehicle limit load coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile testing, in particular to a method for determining a vehicle's dynamic limit load coefficient based on a suspension system. Background Art

[0002] Currently, during vehicle development, the actual ultimate load of a vehicle fluctuates significantly due to weight adjustments and real-time configuration changes. Failure to quickly detect the vehicle's actual ultimate load and promptly adjust the design can lead to serious issues later in the development process, such as limited chassis calibration range, improper tire clearance design, tire interference, and numerous strength and durability issues. This can significantly limit project rectification costs and timelines. Furthermore, current testing of vehicle ultimate loads is often complex, time-consuming, and inefficient. To address these challenges, we have developed a method for determining the vehicle's dynamic ultimate load coefficient based on the suspension system to overcome these issues. Summary of the Invention

[0003] The object of the present invention is to provide a method for determining the dynamic limit load coefficient of a vehicle based on a suspension system, which is used to solve the above technical problems.

[0004] The embodiments of the present invention are achieved through the following technical solutions:

[0005] A method for determining a vehicle's dynamic limit load coefficient based on a suspension system, the method comprising the following steps:

[0006] Modify the wheel hub fenders of the vehicle to a set degree so that the wheel friction marks can be displayed when the vehicle is subjected to a dynamic test under extreme road conditions, and mark the corresponding modified areas. After the dynamic test under extreme road conditions, obtain the marked marks of the vehicle;

[0007] The vehicle's marked traces are visualized and the vehicle is processed to a set degree so that the vehicle's tires are in contact with the vehicle's marked traces and the relative geometric trajectory of the vehicle's tires and tires is consistent. Measurements are then taken to obtain a static measurement value ΔS2; ΔS2 can be defined as the distance from the shock absorber's upper end cover to the lower surface of the shock absorber's upper mounting seat under impact limit conditions.

[0008] The static measurement value ΔS2 is calculated through the suspension disturbance comparison algorithm to obtain the buffer block compression ΔS1 and the spring compression ΔS. The buffer block compression ΔS1 and the spring compression ΔS are combined and reversely calculated through the first setting formula, the second setting formula and the third setting formula to obtain the vehicle limit load coefficient μ.

[0009] Among them, the suspension disturbance comparison algorithm is specifically as follows: the static measurement value ΔS2 is input into the motion mechanism DMU so that the measurement value is consistent with the static measurement value ΔS2, and the buffer block compression amount ΔS1 and the spring compression amount ΔS are obtained by reverse calculation.

[0010] Optionally, the vehicle is modified to a set degree and the corresponding modified areas are marked, specifically: the wheel hub fenders of the vehicle are covered with plasticine and sprayed with developer.

[0011] Optionally, the vehicle is processed to a set degree, specifically: the buffer blocks and springs of the vehicle are removed, and the dampers are installed on the vehicle at the same time, so that the relative geometric trajectory of the vehicle's tires and the vehicle is consistent, the vehicle body is fixed, and the vehicle's tires are loaded upward at a set speed so that the vehicle's tires are in contact with the vehicle's marked traces.

[0012] Optionally, when performing dynamic testing on a vehicle under extreme road conditions, simulation is performed simultaneously through the motion mechanism DMU to verify the consistency between the actual test and the theoretical simulation.

[0013] Optionally, the first setting formula is calculated as follows:

[0014] μ = F1 / [(GVW-M2)×g]

[0015] Among them, GVW is the single-sided wheel load of a fully loaded vehicle; M2 is the unsprung mass of 1 / 4 of the vehicle's suspension; g is the acceleration of gravity; μ is the vehicle's ultimate impact safety factor; and F1 is the maximum load that the vehicle can withstand.

[0016] Optionally, the second setting formula is calculated as follows:

[0017] F1=F2×η1+F3×η2

[0018] Among them, F2 is the load of the spring at the limit load; η1 is the force transmission ratio of the spring; F3 is the load of the buffer block at the limit load; η2 is the force transmission ratio of the buffer block.

[0019] Optionally, the third setting formula is calculated as follows:

[0020] F2=ΔS×C1

[0021] Where ΔS is the spring compression and C1 is the spring linear stiffness.

[0022] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0023] The present invention can quickly verify the actual ultimate impact load coefficient of the vehicle, provide relatively accurate data for the boundary input of vehicle strength and durability calculation, and provide more accurate data for vehicle turning angle distribution, handling optimization, tire envelope design, and optimized wheel arch clearance. It is faster and more cost-effective than collecting road spectra and then simulating through four channels, and does not have the limitations of expensive test equipment and the economic and time costs of complex data post-processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of a method for determining a vehicle's dynamic limit load coefficient based on a suspension system provided by the present invention;

[0025] Figure 2 A schematic diagram of a curve showing the mechanical properties of the buffer block provided by the present invention;

[0026] Figure 3 This is a cross-sectional schematic diagram of the shock absorber provided by the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0028] like Figure 1 As shown, the present invention provides a method for determining the dynamic limit load coefficient of a vehicle based on a suspension system, the method comprising the steps of:

[0029] Variable definitions for vehicle limit load calculation:

[0030] When the vehicle is subjected to extreme impact, the suspension travel reaches the maximum upper stop point and the vehicle is subjected to the maximum load F 1， The formula is as follows:

[0031] F1=(GVW-M2)×g×μ (1)

[0032] Where: GVW - fully loaded vehicle single wheel load, kg; M2 - vehicle 1 / 4 suspension unsprung mass, kg; g - acceleration due to gravity, 9.8 m / s 2 ;μ-vehicle ultimate impact safety factor, F1-vehicle maximum load, N;

[0033] The vehicle safety factor μ is initially set at 2.5G~3G for passenger car designs. However, in the middle of actual vehicle development, after the tooling vehicle is delivered, the load factor needs to be verified. The formula is as follows:

[0034] μ= F1 / [(GVW-M2)×g] (2)

[0035] Where: GVW - fully loaded vehicle single wheel load, kg; M2 - vehicle 1 / 4 suspension unsprung mass, kg; g - acceleration due to gravity, 9.8 m / s 2 ;μ-vehicle ultimate impact safety factor, F1-vehicle maximum load, N;

[0036] The maximum impact load F1 of a single wheel of a vehicle is as follows:

[0037] F1=F2×η1+F3×η2(3)

[0038] Where, F1 is the maximum load on the vehicle, in N; F2 is the load on the spring at the ultimate load, in N; η1 is the force transfer ratio of the spring (i.e., the inverse of the spring leverage ratio); F3 is the load on the buffer at the ultimate load, in N; η2 is the force transfer ratio of the buffer (i.e., the inverse of the buffer leverage ratio);

[0039] Calculation of vehicle spring load points:

[0040] F2=ΔS×C1(4)

[0041] Where, ΔS is the deformation of the spring under impact load, mm; C1 is the linear stiffness of the spring, N / mm;

[0042] Vehicle buffer block load point calculation:

[0043] Since the buffer block curve is generally a nonlinear curve, the mechanical characteristic curve of the buffer block is tested by the equipment, and the deformation is intercepted to obtain the force value F3;

[0044] like Figure 3 As shown, plasticine is appropriately applied near the bulge of the vehicle and sprayed with developer. The purpose is to leave friction marks between the wheels and the rubber when the vehicle is under extreme working conditions, which is used to mark the extreme movement position of the vehicle tires and verify the consistency between the actual and theoretical simulations through DMU simulation of the motion mechanism.

[0045] The processed vehicle shows traces and is made visible. The vehicle's buffer blocks and springs are directly removed, and a damper must be installed to ensure that the relative geometric motion trajectory of the wheel and the vehicle remains unchanged. The vehicle body is fixed, and the wheel is slowly loaded upward to ensure that the wheel is in contact with the display trace, and the ΔS2 value is measured.

[0046] Through the ΔS2 value and the suspension disturbance comparison calculation, the spring compression ΔS and the buffer block compression ΔS1 are obtained. The F2 and F3 values ​​are obtained through formula (4), and the F1 value is obtained through formula (3). Finally, the load coefficient μ value is obtained through formula (2). The vehicle limit load coefficient can be quickly revised to provide a basis for design.

[0047] In view of the above, the present invention provides one embodiment:

[0048] In the later stages of vehicle development, a certain vehicle model experienced significant interference between the wheels and hubcaps, resulting in insufficient roll support and affecting the vehicle's cornering stability. Investigations revealed that the hubcaps, wheel motion envelope, and disturbance distribution were all consistent with the theoretical design. Initial suspicions arose that there was a problem with the vehicle's ultimate load coefficient setting at the beginning of the design.

[0049] The troubleshooting steps are as follows:

[0050] (1) After simple vehicle modification and extreme condition testing, simple calculations were performed on the vehicle, and the ΔS2 value of the vehicle was found to be 56 mm.

[0051] like Figure 2 As shown, the obtained F3 value is 13000N;

[0052] According to formulas (2) to (4), the vehicle limit load coefficient μ is 4.7G.

[0053] The ultimate load factor set at the beginning of the project development was 3.0G. The vehicle's actual ultimate load factor of 4.7G far exceeded the load factor determined at the beginning of the design. By redistributing the suspension disturbance and mechanical characteristic curve based on the vehicle's actual ultimate load, the problem was solved relatively perfectly, consistent with the expected target properties.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for determining the dynamic limit load coefficient of a vehicle based on a suspension system, characterized in that: The steps of the method include: Modify the wheel hub fenders of the vehicle to a set degree so that the wheel friction marks can be displayed when the vehicle is subjected to a dynamic test under extreme road conditions, and mark the corresponding modified areas. After the dynamic test under extreme road conditions, obtain the marked marks of the vehicle; The vehicle's markings are visualized and the vehicle is processed to a set degree so that the vehicle's tires are in contact with the markings and the relative geometric trajectory of the tires and the vehicle is consistent. Measurements are then taken to obtain a static measurement value, ΔS2. ΔS2 is defined as the distance from the shock absorber's upper end cap to the lower surface of the shock absorber's upper mounting seat under the impact limit condition. The static measurement value ΔS2 is calculated using the suspension disturbance comparison algorithm to obtain the buffer block compression ΔS1 and the spring compression ΔS. The buffer block compression ΔS1 and the spring compression ΔS are combined and reversely calculated using the first setting formula, the second setting formula, and the third setting formula to obtain the vehicle limit load coefficient μ. The suspension disturbance comparison algorithm specifically includes: inputting the static measurement value ΔS2 into the motion mechanism DMU so that the measurement value is consistent with the static measurement value ΔS2, thereby reversely calculating to obtain the buffer block compression ΔS1 and the spring compression ΔS; The calculation formula of the first setting formula is as follows: μ = F1 / [(GVW-M2)×g] Where GVW is the single-side wheel load of a fully loaded vehicle; M2 is the unsprung mass of 1 / 4 of the vehicle; g is the acceleration of gravity; μ is the vehicle's ultimate impact safety factor; F1 is the maximum load the vehicle can withstand; The calculation formula of the second setting formula is as follows: F1=F2×η1+F3×η2 Where F2 is the load of the spring at the limit load; η1 is the force transmission ratio of the spring; F3 is the load of the buffer block at the limit load; η2 is the force transmission ratio of the buffer block; The calculation formula of the third setting formula is as follows: F2=ΔS×C1 Where ΔS is the spring compression and C1 is the spring linear stiffness.

2. The method for determining the dynamic limit load coefficient of a vehicle based on a suspension system according to claim 1, characterized in that: The vehicle is modified to a set degree and the corresponding modified areas are marked, specifically: the wheel hub fenders of the vehicle are covered with plasticine and sprayed with developer.

3. The method for determining the dynamic limit load coefficient of a vehicle based on a suspension system according to claim 1, characterized in that: The vehicle is processed to a set degree, specifically: the buffer blocks and springs of the vehicle are removed, and the dampers are installed on the vehicle at the same time, so that the relative geometric trajectory of the vehicle's tires and the vehicle is consistent, the vehicle body is fixed, and the vehicle's tires are loaded upward at a set speed so that the vehicle's tires are in contact with the vehicle's marked traces.

4. The method for determining the vehicle dynamic limit load coefficient based on the suspension system according to claim 1, characterized in that: When conducting dynamic tests on vehicles under extreme road conditions, simulations are also performed through the motion mechanism DMU to verify the consistency between the actual test and the theoretical simulation.

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