Dummy head displacement measurement method and system based on sensor and head model

Abstract

The invention relates to the technical field of vehicle collision measurement, in particular to a dummy head displacement measurement method and system based on a sensor and a head model, and the method comprises the steps: marking a camera, a body-in-white backboard reference point and a dummy head key position in a test scene before a test is started, and forming corresponding marking points; recording an initial three-dimensional coordinate corresponding to each mark point through a three-coordinate measuring instrument; parameters of acceleration sensors arranged on the mass center of the body in white and the mass center of the head of the dummy are set; after the simulation collision test is finished, collecting video data shot by the camera and acceleration data recorded by the acceleration sensor; determining displacements of the mark points on the key positions of the head of the dummy in X, Y and Z, and outputting a displacement curve corresponding to the mark points on the key positions of the head of the dummy; and determining the relative displacement of the corresponding dummy mass center in the X, Y and Z directions at the Tmax moment.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle collision measurement, and in particular to a method and system for measuring dummy head displacement based on a sensor and a head model. Background Art

[0002] In a side impact, the nearside occupant on the impacted side suffers direct injuries, while the farside occupant on the non-impacted side may suffer various injuries due to head or shoulder contact between occupants. To improve a vehicle's ability to protect farside occupants, regulations around the world have introduced farside occupant protection assessment programs.

[0003] The current mainstream test method for evaluating far-end occupant protection is the far-end occupant protection test. This test uses a sliding platform to carry the vehicle body-in-white and accessory components, combined with a dummy model, to simulate typical operating conditions such as side impacts with a deformable moving barrier and side impacts with a pole. The core basis for determining the test results is whether the maximum deflection of the dummy's head exceeds a pre-defined deflection zone / line. Different zones correspond to different safety ratings.

[0004] However, existing technologies have significant limitations: during actual collisions, the dummy's head often blocks some marker points due to airbag deployment, resulting in the inability of pure visual video analysis to accurately capture the dynamic trajectory of the head's center of mass and key markers, making it difficult to accurately determine the maximum displacement position, affecting the reliability of the test results and the objectivity of the scoring.

[0005] Based on this, there is an urgent need for a dummy head displacement measurement method and system based on sensors and head models, which can achieve accurate and reliable measurement of the dummy head displacement during a collision, greatly improving the measurement reliability and accuracy of the dummy head displacement. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a method and system for measuring dummy head displacement based on sensors and a head model, which can achieve accurate and reliable measurement of the dummy head displacement during a collision, greatly improving the measurement reliability and accuracy of the dummy head displacement.

[0007] In order to achieve the above object, a method for measuring dummy head displacement based on a sensor and a head model is provided, comprising the following steps: S1. Before the test begins, mark the camera, the vehicle body-in-white backplane reference points, and the key locations of the dummy's head in the test scene to form corresponding marking points. Attach reflective markers to the marking points and record the initial three-dimensional coordinates corresponding to each marking point using a three-dimensional coordinate measuring machine. S2. Record the internal and external parameter data of the camera before the test begins; S3. Setting parameters of the acceleration sensors provided on the body-in-white and the center of mass of the dummy's head; S4. Input the pre-collected real vehicle waveforms into the slide device in the test scene. After all equipment is prepared, conduct a simulated collision test. S5. After the simulated collision test is completed, collecting the video data captured by the camera and the acceleration data recorded by the acceleration sensor; S6. Determine the displacement of the marking points at key locations on the dummy's head in the X, Y, and Z directions based on the collected video data and the camera's internal and external parameter data. Output the displacement curve corresponding to the marking points at key locations on the dummy's head. Based on the displacement curve, find the time Tmax corresponding to the initial start signal of the slide equipment. S7. Determine the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax based on the collected acceleration data, video data, and Tmax.

[0008] The technical principles and effects of this solution: In this solution, a camera is used to visually capture key locations on the dummy's head, which is affixed with reflective markers, and reference points on the body-in-white (BIW) backplate. By analyzing the two-dimensional coordinate changes of the marker points in the image and combining them with internal and external camera parameters (such as focal length, optical center, and distortion coefficient), the three-dimensional spatial coordinate changes of the marker points are calculated, thereby obtaining displacement data for key locations on the dummy's head. Acceleration sensors are deployed at the center of mass of the BIW and the dummy's head to collect acceleration signals in real time during the collision process. By integrating the acceleration data (first integration for velocity, second integration for displacement) and combining it with time synchronization technology, the inertial displacement information of the dummy's center of mass during the collision can be obtained.

[0009] By establishing the time reference point Tmax through the initial collision signal (the moment the slide starts), the displacement curve measured by vision and the acceleration data measured by inertia are aligned on the time axis. The synchronized data at this moment is used to eliminate the sensor delay error, realizing the complementary verification of the two measurement methods, and ultimately accurately calculating the relative displacement of the dummy's center of mass.

[0010] This solution determines the maximum displacement of the dummy head by combining video analysis and sensor data calculation, which can improve the accuracy of test results. Video analysis can provide a continuous motion trajectory of the marker point (such as the time-displacement curve output by the S6), while acceleration integral calculation can cover the center of mass motion data of the entire time domain. The combination of the two forms the dual guarantee of "real-time tracking of key feature points + overall center of mass motion modeling."

[0011] By independently calculating the center of mass displacement using acceleration sensor data, the system can infer the overall head position based on the center of mass trajectory, ensuring precise positioning at the time Tmax, even in extreme cases where vision is completely lost. Even when the dummy's head is partially obscured by the airbag, this system can replace pure vision to determine the dummy's maximum head displacement, achieving high accuracy and precision. This enables precise and reliable measurement of the dummy's head displacement during a collision, significantly improving the reliability and accuracy of head displacement measurements.

[0012] Furthermore, the key positions of the dummy's head include the top of the dummy's head, the forehead, the mandible and the center of mass of the dummy.

[0013] Beneficial Effects: By attaching reflective markers to multiple key points, such as the top of the head, forehead, and jaw, and combining them with the center of mass, a three-dimensional spatial positioning reference system for the dummy head was constructed. These key locations cover the main contours and center of mass of the head, accurately describing the head posture from two dimensions: geometry and mass distribution. This provides multi-dimensional reference points for subsequent video tracking and trajectory calculation, avoiding the positioning errors that may exist with a single marker.

[0014] In video analysis, markers at multiple key locations can be verified against each other through triangulation, reducing trajectory interruptions caused by occlusion or loss of a single marker. For example, when the top of the head marker is partially blocked by the airbag, the motion trajectory of the forehead and mandibular markers can be interpolated to ensure the continuity and accuracy of the overall head motion trajectory. At the same time, the center of mass position is directly measured by the accelerometer, and the center of mass displacement is calculated by integration, forming a dual verification of "geometric shape-center of mass" with the marker trajectory, further eliminating errors from a single data source. Furthermore, the formula for determining the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax in S7 is:

[0015] Where, is the relative displacement of the head mass center relative to the B-pillar of the body in a certain direction at time t, is the relative displacement of the head mass center relative to the B-pillar of the body-in-white at time t=0, is the relative velocity of the head mass center relative to the B-pillar of the body-in-white at time t=0, It is the relative acceleration of the dummy's center of mass in one of the three directions: X, Y, and Z.

[0016] Beneficial Effects: Applying this formula separately in the X, Y, and Z directions decouples the head's motion components in three-dimensional space (such as lateral shift, longitudinal tilt, and vertical jump). This facilitates analysis of the independent impact of displacements in different directions on occupant injury (for example, whether the lateral head offset corresponding to the maximum Y displacement exceeds the identification line), providing refined data support for subsequent 3D model overlay.

[0017] The formula calculation result (center of mass displacement) and the marker point trajectory obtained by video analysis form a dual-source data verification of "center of mass-geometric shape".

[0018] Furthermore, the method further includes S8, constructing a 3D model of the dummy head, drawing offset lines in the 3D model of the dummy head, and marking the dummy head top position, dummy forehead position, dummy mandibular position, and dummy center of mass position on the model; S9. Based on the relative displacement of the dummy's center of mass in the X, Y, and Z directions at time Tmax, find the position of the dummy's head 3D model at time Tmax, and determine whether the offset line on the dummy's head 3D model at time Tmax exceeds the preset offset area to obtain the corresponding test result data.

[0019] Beneficial Effects: By constructing a dummy head model, the head's geometric shape (such as surface curvature and relative positions of markers) can be accurately restored. Offset lines and key locations (top of head, forehead, mandible, and center of mass) can be superimposed, transforming abstract coordinate data into an intuitive three-dimensional spatial model. For example, by marking the relative position of the center of mass B and the offset marker surface in the model, changes in the head's posture (such as roll and pitch angles) during a collision can be directly observed, avoiding the spatial perception bias that often arises from judging displacement solely through two-dimensional coordinate values.

[0020] When the dummy's head is partially blocked by the airbag, purely visual methods cannot identify the position of the marker points through video. However, the 3D model can drive the dynamic displacement of the model based on sensor data, combined with the preset offset area, to accurately determine whether the head has crossed the boundary even in the absence of visual input.

[0021] Converting abstract displacement data into intuitive and verifiable spatial visualization results not only breaks through the limitations of traditional visual solutions in occlusion scenarios, but also improves the accuracy, efficiency and engineering application value of remote occupant protection tests through multi-source data fusion, automated evaluation and in-depth mechanism analysis.

[0022] The present invention also provides a dummy head displacement measurement system based on a sensor and a head model, and uses the above-mentioned dummy head displacement measurement method based on a sensor and a head model. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a flow chart of a method for measuring dummy head displacement based on sensors and a head model in Embodiment 1 of the present invention.

[0024] Figure 2 This is a function curve diagram of time-displacement in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The following is further described in detail through specific implementation methods: Example 1 The dummy head displacement measurement method based on sensors and head models is basically as follows Figure 1 As shown, the following steps are included: S1. Before the test begins, mark the camera, reference points on the BIW backplane, and key locations on the dummy's head in the test scene. Reflective markers are affixed to these locations, and the initial three-dimensional coordinates corresponding to each marker are recorded using a coordinate measuring machine. Key locations on the dummy's head include the top of the head, forehead, jaw, and center of mass. In this embodiment, a vehicle coordinate system consistent with the test scene is established in the measurement software (typically with the BIW geometric center as the origin, the X-axis along the longitudinal direction of the vehicle, the Y-axis along the transverse direction, and the Z-axis along the vertical direction). This ensures that subsequent measurement data is consistent with the test coordinate system. Circular reflective markers with a diameter of 2-5 mm (e.g., ceramic or glass) are used to ensure high contrast and reflective efficiency within the camera's field of view. After cleaning the surface of the camera, the reference points on the back panel of the vehicle body (such as the B-pillar reference hole), and the key positions of the dummy's head (top of the head, forehead, mandible, and center of mass), use high-temperature resistant glue to stick the marking points, ensuring that the center of the marking point coincides with the geometric center of the measured position (for example, the center of mass marking point needs to be aligned with the center of mass identification hole of the dummy's head). For positions that are difficult to observe directly (such as the inside of the dummy's mandible), auxiliary tooling (such as a telescopic rod equipped with a miniature camera) can be used to assist in confirming the position of the marking point to avoid obstruction or offset. Use the probe of the measuring instrument to touch the center of the marking point one by one to trigger the point sampling function. The software automatically records the X, Y, and Z coordinate values of the point in the vehicle body coordinate system. For the curved surface marking points of the dummy's head (such as the arc area on the top of the head), the probe angle needs to be adjusted to ensure vertical touch to reduce cosine error.

[0026] S2. Record the internal and external parameter data of the camera before the test begins; S3. Setting parameters of the acceleration sensors provided on the body-in-white and the center of mass of the dummy's head; S4. Input the pre-collected real vehicle waveforms into the slide device in the test scene. After all equipment is prepared, conduct a simulated collision test. S5. After the simulated collision test is completed, collecting the video data captured by the camera and the acceleration data recorded by the acceleration sensor; S6. Determine the displacement of the markers at key locations on the dummy's head in the X, Y, and Z directions based on the collected video data and the camera's internal and external parameter data, and output the displacement curve corresponding to the markers at key locations on the dummy's head. Based on the displacement curve, find the time Tmax corresponding to the initial start signal of the slide device. In this embodiment, the camera's internal and external parameters (focal length, pixel size, etc.) recorded before the test and the initial three-dimensional coordinates of the markers measured by three-coordinate measurement are used to convert the two-dimensional pixel coordinates (u, v) into three-dimensional world coordinates (X, Y, Z) through the perspective projection transformation formula, and output the corresponding time-displacement function in the three directions of X, Y, and Z. Figure 2 As shown in the figure, the corresponding time Tmax is found through the maximum value in the Y direction (this time is taken as the time 0 when the initial departure signal T0 given by the slide).

[0027] S7. Determine the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax based on the collected acceleration data, video data, and Tmax.

[0028] The formula for determining the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax in S7 is:

[0029] Where, is the relative displacement of the head mass center relative to the B-pillar of the body in a certain direction at time t, is the relative displacement of the head mass center relative to the B-pillar of the body-in-white at time t=0, is the relative velocity of the head mass center relative to the B-pillar of the body-in-white at time t=0, It is the relative acceleration of the dummy's center of mass in one of the three directions: X, Y, and Z.

[0030] The method further includes S8, constructing a 3D model of the dummy head, drawing offset lines in the 3D model of the dummy head, and marking a top position of the dummy head, a forehead position of the dummy, a mandibular position of the dummy, and a center of mass position of the dummy on the model; S9. Based on the relative displacement of the dummy's center of mass in the X, Y, and Z directions at time Tmax, find the position of the dummy's head 3D model at time Tmax, and determine whether the offset line on the dummy's head 3D model at time Tmax exceeds the preset offset area to obtain the corresponding test result data.

[0031] This embodiment also discloses a dummy head displacement measurement system based on a sensor and a head model, and uses the above-mentioned dummy head displacement measurement method based on a sensor and a head model.

[0032] The above is only an embodiment of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is excessively described here. Ordinary technicians in the relevant field are aware of all common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for measuring dummy head displacement based on a sensor and a head model, characterized by: The following steps are involved: S1. Before the test begins, mark the camera, the vehicle body-in-white backplane reference points, and the key locations of the dummy's head in the test scene to form corresponding marking points. Attach reflective markers to the marking points and record the initial three-dimensional coordinates corresponding to each marking point using a three-dimensional coordinate measuring machine. S2. Record the internal and external parameter data of the camera before the test begins; S3. Setting parameters of the acceleration sensors provided on the body-in-white and the center of mass of the dummy's head; S4. Input the pre-collected real vehicle waveforms into the slide device in the test scene. After all equipment is prepared, conduct a simulated collision test. S5. After the simulated collision test is completed, collecting the video data captured by the camera and the acceleration data recorded by the acceleration sensor; S6. Determine the displacement of the marking points at key locations on the dummy's head in the X, Y, and Z directions based on the collected video data and the camera's internal and external parameter data. Output the displacement curve corresponding to the marking points at key locations on the dummy's head. Based on the displacement curve, find the time Tmax corresponding to the initial start signal of the slide equipment. S7. Determine the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax based on the collected acceleration data, video data, and Tmax.

2. The method for measuring dummy head displacement based on a sensor and a head model according to claim 1, characterized in that: The key positions of the dummy's head include the top of the dummy's head, the forehead, the mandible and the center of mass of the dummy.

3. The method for measuring dummy head displacement based on a sensor and a head model according to claim 2, characterized in that: The formula for determining the relative displacement of the dummy's center of mass in the X, Y, and Z directions corresponding to the time Tmax in S7 is: Where, is the relative displacement of the head mass center relative to the B-pillar of the body in a certain direction at time t, is the relative displacement of the head mass center relative to the B-pillar of the body-in-white at time t=0, is the relative velocity of the head mass center relative to the B-pillar of the body-in-white at time t=0, It is the relative acceleration of the dummy's center of mass in one of the three directions: X, Y, and Z.

4. The method for measuring dummy head displacement based on a sensor and a head model according to claim 3, characterized in that: The method further includes S8, constructing a 3D model of the dummy head, drawing offset lines in the 3D model of the dummy head, and marking a top position of the dummy head, a forehead position of the dummy, a mandibular position of the dummy, and a center of mass position of the dummy on the model; S9. Based on the relative displacement of the dummy's center of mass in the X, Y, and Z directions at time Tmax, find the position of the dummy's head 3D model at time Tmax, and determine whether the offset line on the dummy's head 3D model at time Tmax exceeds the preset offset area to obtain the corresponding test result data.

5. A dummy head displacement measurement system based on sensors and a head model, characterized by: A method for measuring dummy head displacement based on a sensor and a head model according to any one of claims 1 to 4.

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