A method for evaluating optimal parameter settings for knee protection impact areas

Abstract

The present invention discloses an optimal parameter setting evaluation method for dealing with the knee protection impact area, wherein a coordinate system is established with the intersection of the footrest surface and the carpet surface as the origin and the carpet surface as the X-axis; the basic leg contour is extracted and simplified and then placed in the above coordinate system: the heel point B is on the X-axis, and the toe point A is on the footrest surface; the dummy foot size parameters are set as constants, the ankle point C is used as a fixed point, and the knee point D is used as a moving point, and the intersection area corresponding to the IP CAS is calculated based on different modeling features and foot comfort requirements, so as to evaluate the optimal values ​​of the angle θ between the footrest surface and the carpet surface and the angle α between the sole plane and the carpet surface. The present invention effectively solves the problem of setting optimal parameters in the early stage of project development.

Description

Technical Field

[0001] The invention belongs to the technical field of collision safety, and in particular is an optimal parameter setting evaluation method for a knee protection impact area. Background Art

[0002] According to the latest regulations of the 2021 edition of CNCAP and ENCAP, a knee impact assessment will be conducted for frontal collisions, in which the impact area of ​​the legs will be set according to different vehicle styling boundaries and combined with specific human body size information. If the vehicle needs to meet this evaluation requirement during the development process, it is necessary to summarize the control methods for the styling surface and spatial structure. Only in this way can the design implementation of knee-mapping (knee impact protection evaluation method, which determines the protection of the vehicle to the occupant's knees during a collision) be tested in the styling feasibility study and engineering feasibility study stages.

[0003] The Chinese patent "Dummy lower limb impact test method", publication number CN104931221A, publication date 2015.09.23, discloses a dummy lower limb impact test method, using a dummy lower limb impact test equipment, which includes an impact test object device, a dummy lower limb, a guide track, a sliding device, a foot loading device, a loading device, a stopping device, a sensor group and a host computer; step 1, preparation work; step 2, loading process; step 3, release process; step 4. Data collection and analysis.

[0004] Chinese patent "Device and sled test bench for verifying the knee collision performance of automobile dashboard", publication number CN112098111A, publication date 2020.12.18, a device and sled test bench for verifying the knee collision performance of automobile dashboard. The device for verifying the knee collision performance of automobile dashboard includes a base, a small slide, a buffer spring assembly, a slide rail, a footrest assembly, a collision dummy leg, and a locking mechanism assembly. It is a knee collision test method for the dashboard subsystem based on a sled test bench. First, the automobile dashboard assembly and its fixing tooling and the mechanism of the present invention are installed on the pulley test bench; then, the legs of the collision dummy are placed on the mechanism of the present invention according to the sitting posture requirements, wherein the pelvis is installed on the small slide of the present invention, and the small slide is installed on the slide rail in the mechanism of the present invention and performs forward and backward linear motion, and the feet of the dummy are placed or fixed on the footrest in the mechanism of the present invention; finally, the pulley test bench launches and provides the speed and energy of the dummy legs in the mechanism of the present invention to hit the dashboard, pushing the dummy legs to rotate around the ankles to hit the dashboard, and during this movement, the damage performance of the dummy legs during the collision is simultaneously monitored and obtained.

[0005] During a collision, the knee moves and contacts the surface of the instrument panel. The specific area of ​​the knee contact point is divided into the following: Figure 1As shown, the knee contact point is the first coordinate point that needs to be confirmed during development, and it is also the key verification indicator that needs to be considered in the styling design stage. Figure 1 The division diagram is derived from the CNCAP 2021 official evaluation procedures, and the wireframe area is the evaluation range drawn based on the knee contact point.

[0006] The existing technology is to set the knee-impact area by placing a dummy and adjusting the contact area according to the boundary of the carpet and the footrest to determine the knee-mapping risk. The process is too slow and cannot form a design guide for the instrument shape and the angle of the footrest. Avoid the subsequent damage to the human leg in the real state of the vehicle. Summary of the invention

[0007] The purpose of the present invention is to provide an optimal parameter setting evaluation method for coping with a knee protection impact area, which can obtain the optimal parameters in the early stage of project development.

[0008] In order to achieve the above-mentioned object, the present invention is designed to evaluate the optimal parameter setting for the knee protection impact area, which is characterized by:

[0009] A coordinate system is established with the intersection of the footrest surface and the carpet surface as the origin and the carpet surface as the X-axis; the basic outline of the leg is extracted, simplified and placed in the above coordinate system: the heel point B is on the X-axis, and the toe point A is on the footrest surface;

[0010] The dummy foot size parameters are set as constants, the ankle point C is taken as the fixed point, and the knee point D is taken as the moving point. The intersection area of ​​the corresponding IP CAS is calculated based on different modeling features and foot comfort requirements, so as to evaluate the optimal values ​​of the angle θ between the foot rest surface and the carpet surface, and the angle α between the sole plane and the carpet surface.

[0011] Preferably, the coordinates of point A are (X1, Y1), the coordinates of point B are (X2, 0), the slope of straight line segment AC is K1, and the slope of straight line segment BC is K2; the coordinates of ankle point C are:

[0012] Xc=(K1·X1-K2·X2-Y1) / (K1-K2), Yc=(K1·K2(X1-X2)-K2·Y1) / (K1-K2);

[0013] K1=tan(α-∠BAC), K2= tan(α+∠ABC);

[0014] The motion trajectory of point D is , R is the dimension value from the focus of the test dummy to the center point of the knee sensor.

[0015] Preferably, the coordinate position of the heel point is corrected using the compression stroke of the rest surface.

[0016] Further preferably, the Poisson's ratio and elastic modulus are calculated according to the material coefficient of the resting area, so as to infer the corresponding compression stroke, that is, the strain ε: stress = calf compression force = elastic modulus E of the carpet surface * strain ε; the calf compression force is determined according to the "C-NCAP Management Rules".

[0017] Still more preferably, the strain ε parameter value is corrected to the dimensional coordinate of point B (X2 - ε*COSα, 0 - ε*sinα).

[0018] Preferably, θ ranges from 20° to 60°.

[0019] More preferably, θ is in the range of 30° to 50°.

[0020] Preferably, the range of α is 15° to 55°.

[0021] More preferably, |θ-α|≤5°.

[0022] The beneficial effects of the present invention are as follows: the present invention effectively solves the problem of setting optimal parameters in the early stage of project development. The present invention sets a part of parameters as evaluation constants according to the early parameters of the vehicle model and the development goals, and outputs the corresponding evaluation model by simplifying the calculation, which is used to calibrate parameters such as floor angle and modeling surface in the early stage of development; the present invention adds control variables for the compression force and bottom strain of the human leg as input boundaries. The present invention can quickly and conveniently output the corresponding optimal angle parameters and foot positions under the specified project boundaries and comfort boundaries, as well as suggestions for modeling surfaces. The present invention can be used in the early stage evaluation of people of different body shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the knee assessment area division in the "C-NCAP Management Rules" (2021 Edition)

[0024] Figure 2 It is a schematic diagram of the coordinate system established by the present invention DETAILED DESCRIPTION

[0025] The technical solution (including the preferred technical solution) of the present invention is further described in detail below by means of the accompanying drawings and by listing some optional embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 2As shown, the optimal parameter setting evaluation method for the knee protection impact area designed by the present invention is to establish a coordinate system with the intersection of the footrest surface and the carpet surface as the origin and the carpet surface as the X-axis; the basic contour of the leg is extracted, simplified and placed in the above coordinate system: the heel point B is on the X-axis, and the toe point A is on the footrest surface;

[0027] The dummy foot size parameters are set as constants, the ankle point C is taken as the fixed point, and the knee point D is taken as the moving point. The intersection area of ​​the corresponding IP CAS is calculated based on different modeling features and foot comfort requirements, so as to evaluate the optimal values ​​of the angle θ between the foot rest surface and the carpet surface, and the angle α between the sole plane and the carpet surface.

[0028] The present invention extracts the basic outline of the leg and simplifies it into a corresponding motion relationship diagram. Let angle θ and angle α be the input angle information, the coordinates of point A are (X1, Y1), the coordinates of point B are (X2, 0), the slope of straight line segment AC is K1, the slope of straight line segment BC is K2, and the straight line segment AB is a simplified representation from toe to heel. The specific calculation process is as follows:

[0029] Slope K1 = tan (α - ∠BAC); Slope K2 = tan (α + ∠ABC)

[0030] Solve the angle between line segment AC and line segment BC as:

[0031] The coordinates of point C are:

[0032] Xc=(K1·X1-K2·X2-Y1) / (K1-K2), Yc=(K1·K2(X1-X2)-K2·Y1) / (K1-K2);

[0033] The motion trajectory of the corresponding point D is , R is the dimension value from the focus of the test dummy to the center point of the knee sensor.

[0034] In the early stage of project development, based on the decomposition of the project safety performance development goals, the tibia coefficient TI and the calf compression force F of the leg are set; the Poisson's ratio and elastic modulus are calculated according to the material coefficient of the resting area, and the corresponding compression stroke is inversely deduced, and the compression stroke is the strain ε. That is, stress F = calf compression force = elastic modulus E of the carpet surface * strain ε.

[0035] The tibia index and calf compression force have corresponding indicators for control and assessment. It is generally believed that if the tibia index is less than 0.4 and the calf compression force is less than 2KN, the possibility of injury to the calf is low. The specific indicators are shown in Table 1.

[0036] Table 1 Evaluation indexes of front row dummy lower leg in 100% frontal collision

[0037]

[0038] Correct the strain ε parameter value to the dimensional coordinates of point B (X2 - ε*COSα, 0 - ε*sinα).

[0039] In the early stage of project development, the parameters a, b, and c are set based on the set dummy, and the calf compression force F and strain ε are set according to the safety level required by the vehicle model. After setting, the above parameters are substituted into the simplified file as constants.

[0040] The angle θ and angle α are treated as variables, and the corresponding angle θ and angle α values ​​are set based on different styling features and foot comfort requirements. Generally, the angle θ ranges from 20° to 60°, and the angle α value ranges from 15° to 55°. By setting the calculation, the intersection area with the outer surface of the corresponding IP CAS instrument panel can be obtained. Thus, the optimal angle θ and angle α parameter values ​​under the corresponding safety performance, comfort performance, and styling characteristics can be obtained.

[0041] The more comfortable range for the feet is generally θ range 30° ~ 50, and the angle α is generally as close to the angle θ as possible. Preferably, |θ-α|≤5°. Under this trend, the range of the contact point tends to be close to the upper part, affecting the design of the IP shape seam and causing the glove box space to become smaller.

[0042] The present invention can be used to perform screening based on the modeling feature language as much as possible, and evaluate the angle value corresponding to the optimal range.

[0043] Those skilled in the art will readily appreciate that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, replacements, improvements, etc. made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A method for evaluating optimal parameter settings for a knee protection impact area, characterized in that: A coordinate system is established with the intersection of the footrest surface and the carpet surface as the origin and the carpet surface as the X-axis. The basic outline of the leg is extracted, simplified and placed in the above coordinate system: the heel point B is on the X-axis, and the toe point A is on the footrest surface. The dummy foot size parameters are set as constants, with the ankle point C as the fixed point and the knee point D as the moving point. The coordinates of point A are (X1, Y1), the coordinates of point B are (X2, 0), the slope of line segment AC is K1, and the slope of line segment BC is K2; the coordinates of ankle point C are: Xc=(K1·X1-K2·X2-Y1) / (K1-K2), Yc=(K1·K2(X1-X2)-K2·Y1) / (K1-K2); K1=tan(α-∠BAC), K2= tan(α+∠ABC); The motion trajectory of point D is , R is the dimension value from the key point of the test dummy to the center point of the knee sensor; The coordinate position of the heel point B is corrected by the compression stroke of the rest surface. The corrected coordinate of point B is (X2 - ε*COSα, 0 - ε*sinα). The Poisson's ratio and elastic modulus are calculated based on the material coefficient of the rest area, and the corresponding compression stroke is inversely deduced. The compression stroke is the strain ε. The angles θ and α are treated as variables, and the intersection areas of the corresponding IP CAS are calculated based on different styling features and foot comfort requirements, so as to evaluate the optimal values ​​of the angle θ between the foot rest surface and the carpet surface, and the angle α between the foot bottom plane and the carpet surface.

2. The optimal parameter setting evaluation method for the knee protection impact area according to claim 1, characterized in that: Stress F = calf compression force = elastic modulus E of carpet surface * strain ε; calf compression force is determined according to the "C-NCAP Management Rules".

3. The optimal parameter setting evaluation method for the knee protection impact area according to claim 1 or 2, characterized in that: The range of θ is 20° to 60°.

4. The optimal parameter setting evaluation method for coping with the knee protection impact area according to claim 3 is characterized in that: The range of θ is 30° to 50°.

5. The optimal parameter setting evaluation method for coping with the knee protection impact area according to claim 3 is characterized in that: The range of α is 15° to 55°.

6. The optimal parameter setting evaluation method for coping with the knee protection impact area according to claim 4 is characterized in that: The range of α is 15° to 55°.

7. The optimal parameter setting evaluation method for coping with the knee protection impact area according to claim 5 or 6, characterized in that: |θ-α|≤5°.

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