Method for evaluating the aerodynamic handling stability of a vehicle

Abstract

This technology enables the identification of vehicle shape factors that cause aerodynamic fluctuations in a relatively short time using limited data, without relying on large-scale calculations. [Solution] A method for evaluating the aerodynamic steering stability of a vehicle 1, comprising: a first step S1 of measuring the time-series change of pressure p acting on each measurement point 20 of the vehicle 1; a second step S2 of estimating the similarity between the waveform of the fluctuation Mz' of the yaw aerodynamic moment Mz acting due to aerodynamic fluctuations around the vehicle 1 during vehicle driving and the waveform of the fluctuation Mz' of pressure p at each measurement point 20; a third step S3 of measuring the distance L from a reference point 10 of the fluctuation Mz' of the aerodynamic moment Mz to a predetermined measurement point 20; and a fourth step S4 of detecting a location (region 40) that has a large influence on the fluctuation Mz' of the aerodynamic moment Mz based on the results of the first to third steps S1 to S3.

Description

Technical Field

[0001] The present invention relates to a method for evaluating aerodynamic steering stability of a vehicle.

Background Art

[0002] For example, it is known that one of the factors affecting the aerodynamic steering stability of a vehicle is the body shape of the vehicle.

[0003] The flow field around a moving vehicle generates a pressure distribution on the body surface of the vehicle, and as a result, aerodynamic force (hereinafter abbreviated as aerodynamic force) acts around the vehicle body, and fluctuations in the aerodynamic force lead to behavior or vibration of the vehicle body, which affects the driver's steering operation and steering feel.

[0004] In view of the above, in order to improve aerodynamic steering stability, it is necessary to reduce aerodynamic force fluctuations by improving the body shape of the vehicle.

[0005] For example, Patent Document 1 describes that "A vehicle has a travelable vehicle body, and includes side protruding members provided to protrude from the outer surface of the traveling vehicle body, and a specially processed surface having a plurality of recesses formed on the outer surface of the vehicle body by the side protruding members. The side protruding members are arch garnishes provided for a plurality of wheel houses arranged side by side in the front-rear direction on the side surface of the vehicle body and protruding so as to enclose the front and rear wheel houses. The specially processed surface is entirely formed on the surface of the side protruding member that serves as the outer surface of the vehicle body, the plurality of recesses are entirely formed on the specially processed surface, and each of the recesses is formed as a regular hexagonal or regular square opening on the specially processed surface."

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of Invention

[0007] In the above-mentioned Patent Document 1, there are concerns that complex calculations, accumulated data, and parameters will be required to identify the cause of the significant influence of aerodynamics.

[0008] While development has traditionally relied on trial and error based on empirical knowledge, the accuracy of predictions has dramatically improved through the analysis of large-scale calculation results, such as transient calculations, which allow for the identification of shape factors that cause aerodynamic fluctuations. However, the costs involved are high, and verification through wind tunnel testing and other methods remains essential.

[0009] In view of these circumstances, the present invention aims to provide a method for evaluating the aerodynamic handling stability of a vehicle that can identify vehicle shape factors that cause aerodynamic fluctuations in a relatively short time using limited data, without relying on large-scale calculations or the like. [Means for solving the problem]

[0010] Therefore, this invention proposes a method for extracting areas with a high degree of influence by determining the distribution of the degree of influence on aerodynamic fluctuations in a relatively short period of time from time-series data of aerodynamic values ​​obtained from wind tunnel tests and other methods, and pressure values ​​on the vehicle body surface.

[0011] The present invention is a method for evaluating the aerodynamic steering stability of a vehicle, characterized by comprising: a first step of measuring the time-series change of pressure acting on each measurement point of the vehicle; a second step of estimating the similarity between the waveform of fluctuations in the yaw direction aerodynamic moment acting due to fluctuations in the aerodynamics around the vehicle during vehicle operation and the waveform of fluctuations in pressure at each measurement point; a third step of measuring the distance from a reference point for the fluctuations in the aerodynamic moment to a predetermined measurement point; and a fourth step of detecting a location that has a large influence on the fluctuations in the aerodynamic moment based on the results of the first to third steps.

[0012] This configuration allows for the identification of vehicle shape factors that cause aerodynamic fluctuations in a relatively short time using limited data, without relying on large-scale calculations. This is advantageous for evaluating the aerodynamic handling stability of a vehicle. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for evaluating the aerodynamic handling stability of a vehicle that can identify vehicle shape factors that cause aerodynamic fluctuations in a relatively short time using limited data, without relying on large-scale calculations or the like. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows the procedure for evaluating the aerodynamic handling stability of a vehicle according to one embodiment of the present invention. [Figure 2] (a) is a top view of the vehicle, (b) is a left side view of the vehicle, and (c) is a right side view of the vehicle. [Figure 3] (a) is a graph showing the relationship between pressure fluctuations and time, and (b) is a graph showing the relationship between yaw moment and time. [Modes for carrying out the invention]

[0015] The best embodiment for carrying out the present invention will be described in detail below with reference to the accompanying drawings.

[0016] Figures 1 to 3 show an embodiment of the present invention. Figure 2 shows an automobile as vehicle 1. This vehicle 1 has a shape in which a front compartment for housing the engine, motor, etc., protrudes in front of the passenger compartment.

[0017] It is known that the fluctuations Mz' of the yaw aerodynamic moment Mz (hereinafter referred to as yaw moment) acting due to aerodynamic fluctuations around the vehicle during driving significantly affect the stability of driving and steering.

[0018] As is well known, yawing refers to a phenomenon or state called yaw or yawing motion, which is a rotational motion of a vehicle such as direction change, turning, or spin phenomenon acting around the vertical axis (Z-axis) passing through the center of gravity of the vehicle. The force that causes the yawing is referred to as a yawing moment.

[0019] Accordingly, in the method for evaluating aerodynamic steering stability of a vehicle according to the present embodiment, the degree of influence of the pressure acting on the surface of the traveling vehicle (surface pressure p) on the fluctuation Mz' of the yaw moment Mz is determined, and a portion having a large influence on the fluctuation Mz' of the yaw moment Mz is identified.

[0020] The fluctuation Mz' of the yaw moment Mz is greatly affected by the fluctuation p' of the surface pressure p acting on the left and right of the vehicle. Therefore, it is considered that a portion where the fluctuation p' and the fluctuation Mz' are similar, as well as the fluctuation p' there and the distance L from the reference point 10 of the yaw moment Mz are related.

[0021] On the other hand, strictly speaking, as shown in Fig.2(a), the yaw moment Mz is considered to be the result of integrating the locally acting force by multiplying the force F acting in the direction perpendicular to the straight line 30 connecting the reference point 10 and the predetermined measurement point 20 at a certain action point by the distance L of the straight line 30.

[0022] Among these, although it is difficult to locally measure the force F by actual measurement, the surface pressure p at each point can be measured.

[0023] On the other hand, elements that affect the fluctuation Mz' of the yaw moment Mz include the following (1) to (3).

[0024] (1) Time-series change of pressure acting on each measurement point 20 of the vehicle 1.

[0025] (2) Similarity between the waveform of the fluctuation Mz' of the yaw moment Mz and the waveform of the fluctuation amount p' of the pressure p at each of the measurement points.

[0026] (3) Distance from the reference point 10 of the fluctuation Mz' of the yaw moment Mz to the action point.

[0027] By using (1) to (3) above, it is possible to detect locations where the yaw moment Mz has a significant influence on the variation Mz'.

[0028] Therefore, the procedure for improving aerodynamic characteristics will be explained with reference to Figures 1 to 3. Although not shown in the figures, the aerodynamic characteristics improvement method can be performed using an appropriate computer.

[0029] As the first step S1 in Figure 1, as shown in Figure 3(a), the amount of change p' of each surface pressure p is measured as the time-series change of the pressure p acting on each measurement point 20 of the vehicle 1.

[0030] As the second step S2 in Figure 1, as shown in Figures 3(a) and 3(b), the similarity is estimated by calculating the correlation coefficient C between the waveform of the fluctuation Mz' of the yaw moment Mz and the waveform of the fluctuation p' of the surface pressure p at each measurement point 20.

[0031] As the third step S3 in Figure 1, the distance L from the reference point 10 of the yaw moment Mz to the predetermined measurement point 20 is measured, as shown in Figure 2(a).

[0032] As the fourth step S4 in Figure 1, based on the results of the first steps S1 to the third step S3, a region where the yaw moment Mz has a large influence on the variation Mz' is detected. Specifically, the contribution E of the yaw moment Mz is calculated using the following equation 1, and a region with a high contribution E, such as the region 40 in Figures 2(b) and (c), is detected. E = p' × L × C ... Equation 1 From the distributions shown in Figures 2(b) and (c), the locations with a high contribution E are the Rr corners where region 40 exists. This method makes it possible to identify locations where the contribution E of the yaw moment Mz is high.

[0033] As described above, according to embodiments to which the present invention is applied, it becomes possible to identify vehicle shape factors that cause aerodynamic fluctuations in a relatively short time using limited data, without relying on large-scale calculations or the like. This is advantageous when evaluating the aerodynamic handling stability of a vehicle.

[0034] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims and equivalents thereof.

[0035] For example, the above embodiment provides an example of a method for evaluating the aerodynamic steering stability of a vehicle by focusing on the aerodynamic moment Mz in the yaw direction, but the present invention is not limited to this.

[0036] For example, although not shown in the diagram, it is possible to evaluate the aerodynamic handling stability of a vehicle by focusing on the six aerodynamic components (Fx, Fy, Fz, Mx, My, Mz). [Industrial applicability]

[0037] The present invention can be suitably used in a method for evaluating the aerodynamic handling stability of a vehicle. [Explanation of symbols]

[0038] 1 vehicle Mz yaw moment Mz' Variation of yaw moment Mz p surface pressure p' Variation of surface pressure p C Correlation coefficient 10 reference points 20 measurement points 30 A straight line connecting reference point 10 and measurement point 20. F is a force acting perpendicular to the line 30. L is a straight line distance of 30. 40 areas

Claims

[Claim 1] A method for evaluating the aerodynamic handling stability of a vehicle, The first step is to measure the time-series change of the pressure acting on each measurement point of the vehicle, A second step involves estimating the similarity between the waveform of the yaw-direction aerodynamic moment fluctuation acting due to aerodynamic fluctuations around the vehicle during its operation and the waveform of the pressure fluctuation at each measurement point. A third step involves measuring the distance from the reference point for the fluctuation of the aerodynamic moment to a predetermined measurement point, A method for evaluating the aerodynamic handling stability of a vehicle, characterized by comprising a fourth step of detecting a location that has a large influence on the fluctuation of the aerodynamic moment based on the results of the first to third steps.

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