Automotive Safety Testing - 3D Measurement and Analysis of Crash Vehicles
Crash Deformation Analysis
Optical metrology systems provide a significant advance in measurement capability for crash test facilities. These systems are fast, and provide results that document all test results in accordance with regulatory requirements. Deformation analysis can be performed while freely moving around a test vehicle which greatly increases measurement efficiency. Optical measurement systems can incorporate multiple cameras, which makes it possible to observe and measure multiple points at the same time. This is particularly useful for crash dummy positioning. Software is available which will automatically record and report all required data including 3D position of the crash dummy H-point, Knee and Head positions in vehicle coordinates and relative to the seat position. Probes with optical targets can be tracked through wireless links to provide additional information required by test protocols. This data can be collected in real-time on multiple points even if the vehicle is moved during the test. Optical measurement systems also solve difficult measurement problems such as Free Motion Head test requirements.
Real-Time Positioning of Crash Dummies
Free Motion Head Testing
Crash barrier tests, side impact tests, and roll-over tests require pre-crash and post-crash measurement of a large number of points located anywhere on the vehicle. With the ProCam optical measurement system, data is collected with a hand held probe pre-crash and post-crash. A selection of probe tips and extensions makes it possible to reach into all areas of the vehicle including the engine compartment and passenger areas.
The geometrical deformation of the crash vehicle is analyzed with a number of measuring points. Typical tests will require several hundred measuring points which are located inside and underneath the vehicle, on the car body, and in the engine compartment.
The points to be measured are organized in a structured measuring plan. The measuring plan is linked to overview screens which immediately inform the operator about the position of the measuring point on the vehicle. The points already measured are identified in the tree structure in order to provide an overview of the progress of the measurement.
The test vehicle is placed in the measurement area. Most test facilities set up several measurement locations, and move the ProCam systems to the area where the next vehicle is being prepared. The test vehicles can be placed anywhere in the measurement cell.
The operator begins the measurement by locating reference points on the vehicle. The ProCam Crash software permits an alignment with a variable number of points and different kinds of points (elongated hole, circle etc.) which are used to transform into the vehicle coordinate system. Different alignment algorithms (best-fit, 3-2-1 etc.) can be used as desired for each crash vehicle configuration.
The operator begins collection of data points with the mobile ProCam probe. Since the reference system is on the surrounding walls or panels, the operator can move freely from side-to-side or to any location for the next measurement point. No system relocation is required.
The different shapes and sizes of ProCam probe tips offer the user a flexible measuring system which even works in areas difficult to access, such as inside the vehicle or in the engine compartment. The bayonet allows the change of a probe without a new calibration.
Automatic Analysis of the Deformation
During the follow-up Post-Crash measurement all values are compared to the results of the pre-measurement, and the deformation between two points is calculated. Thanks to digital pictures of the crash vehicle -- including a graphic overlay of the deformation vectors -- the user is given a clear overview of the result of the vehicle safety test. The combination of test data with digital pictures provides full documentation of the test.
Crash test regulations provide specifications for dummy placement and record keeping. TraceCam is a multi-camera 3D optical measurement system that provides real-time positioning information for key locations of the dummy in vehicle coordinates. TraceCam is used for sled testing and barrier facilities.
STEP 1: Preparation
To prepare the dummy positioning, the location of reference points on the corresponding side of the vehicle or buck are measured. Reflective targets placed around the door opening are also measured. The 3D co-ordinates of the reflective targets are automatically calculated and become the reference for all future measurements for the vehicle. For sled testing, the buck is measured one time and the file with information about the location of the reference targets is loaded prior to each test. After the positioning system is initialized, a continuous transformation into the coordinate system of the vehicle is performed using the points and information from multiple cameras. Movements of the vehicle which could arise from placing the dummy are immediately compensated.
STEP 2: Positioning of the Dummy
The test setup in the DuPos data base informs about the ideal position of the dummy. The actual position of the dummy is recorded via control points placed on the dummy or on adapters and compared to the ideal position. The difference from actual to ideal position is shown in a coordinate table or in a graphic representation. Since control points on the vehicle are constantly monitored, there is no effect on the measurement if the vehicle moves during the measurement process.
The differences between the target positions and reference positions are displayed graphically and numerically. With all points on the dummy measured and displayed simultaneously in vehicle coordinates, the technician can quickly put the dummy into its target position.
STEP 3: Touch Probe, Report
After the positioning, additional coordinates, distances or angles can be measured with the wireless Active Probe. DuPos software automatically makes all calculations. The results are shown in a report and can be processed individually and exported.
New requirements for FMH testing according to the FMVSS 201 requirements can be met with software which has been incorporated into the Aicon software. FMH tests involve multiple possibilities for positioning the head to the targets. Since endless combinations of the forehead impact zone and the range of horizontal and vertical firing angles are possible, numerical simulation is used to reduce the number of tests. Years of testing by an Aicon partner company have produced a determination of the worst case as well as other relevant combinations. Testing is then performed to validate the simulation. The Aicon software module will automatically provide the position and angle of the head to the target.
A second step of testing will analyze solutions and align critical components relative to their distance to critical or solid impact zones.
This software is in compliance with all legislative requirements. A measurement wizard guides the operator through the test and provides the actual test of the regulation along with visual interpretation of the required measurement points.
Crash tests are indispensable in vehicle development. Crash testing is increasingly complex, and all vehicle designs need to be tested. No test detail is left to chance. The position of the test dummies in the vehicle is precisely determined by government regulations. But how quickly can the test engineer place the dummies in the required position? The TraceCam optical measuring system produced by AICON has been specifically developed for the purpose of dummy positioning.
FORD is using several TraceCAM dummy positioning systems for their sled test applications at their Dearborn test facility. The system provides immediate information about the position of the dummy relative to the sled. With the help of a handheld measuring probe or adapters, the position is recorded in real time, and compared to nominal data.
Accurex engineers installed and support this system. The time saved by using the TraceCam system is particularly valuable. More crash tests administered within a shorter period of time means greater productivity.
FORD uses Four TraceCAM systems
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