Automotive Assessments T/HIS
When the tool is launched in T/HIS you are presented with this window (below). This is where you select what assessments you want to carry out.
The dropdown menus on the left hand side show the regulation being used to carry out the assessments and the version. The model unit system is also shown along with any "Time of first sample" offset that will applied if it was defined in Automotive Assessments PRIMER. Curves will be shifted to start at "Time of first sample" and then any data before t=0 will be discarded.
To select what assessments to carry out, you first need to select which occupant(s) you want to assess.
To select a single occupant, left-click on the one you want to assess. Use shift and left-click or ctrl and left-click to select multiple occupants. If you want to select all the occupants you can press the tick button and to deselect them all press the cross.
You can then select the body part(s) you want to assess.
This will populate the Occupant Assessment Types list with the assessments that can be carried out for the selected body parts and occupants. By default they will all be selected, but you can chose to select only a subset of the list if you don't want to do them all.
You can also select which structure(s) which you want to assess
This will populate the Structure Assessment Types list with the assessments that can be carried out for the selected structures.
You can then chose how the graphs for each assessment should be displayed. By default they will all be put on one page and overwrite any existing graphs, but you can also chose to put each one on a separate page and append them to existing graphs.
Once you are happy with your choices, click to carry out the assessments. T/HIS will extract the data required for each assessment, process it according to the rules set out in the regulation and plot the results on a graph with datums showing allowable limits (where they are defined by the regulation), e.g. the CHEST_COMPRESSION assessment for the driver:
If you have selected multiple occupants the curves for each occupant will be plotted on the same graph if the datum values are the same. If the datum values are different they will be plotted on separate graphs.
The output box at the bottom of the window lists the values and scores from the assessments carried out. Clicking on the '->' for each assessment will highlight the curve used for the assessment (and select the page if it's not on the current page) to make it easy to locate:
Multiple Models
It is also possible to plot results from multiple models on the same graphs. This is useful when you want to compare results between different runs.
First you'll need to load the results from the models you want to compare into T/HIS and then on the workflow menu, select Multiple Models, pick the models you want to compare and press Run. Note that the models need to be of the same crash test type and regulation. If they're not the tool will refuse to run.
The window will then be populated with the occupants and structures from all the selected models, pre-pending them with the model number (M1, M2, etc)
If you wanted to compare the results for a CHEST_COMPRESSION assessment of the driver you would select the occupants in both models, select the chest body part and the CHEST_COMPRESSION assessment type.
Euro NCAP Virtual Far Side Protocol Validation Criterion 2
Automotive Assessments can be used to check Validation Criterion 2, according to Section 6.3 of the Euro NCAP Virtual Far Side Simulation & Assessment Protocol. The Assessment Criteria ratios and differences are calculated and presented in the output table.
If you selected the crash test: Far Side Pole and Version: 2024, in PRIMER, then when you open Automotive Assessments in T/HIS, you will be presented with the window below. Here, you can import and select a test model and choose the assessments you want to carry out.
You can import a test model using the button. You are given control over the Import Configuration to correct any inconsistencies with ISO-MME channel names and units. Once imported, you can choose which model to use as a test model from the combo box.
The output table at the bottom of the window lists the injury values, Validation Criteria 2 ratios and differences (\(r_{AC_{sim}}\), \(r_{AC_{test}}\) and \(d_{AC}\) from Equation 4 of the Euro NCAP VTC protocol) and scores for the assessments carried out.
The following example below explains how \(r_{AC_{sim}}\), \(r_{AC_{test}}\) and \(d_{AC}\) are represented in the output table.
If you select simulation (M1) Driver and test data (T1) Driver in the Occupants selection and click , assessments will be carried out for both M1 and T1, with T1 used as the test model (reference) for both.
- According to equation 4, the \(r_{AC_{sim}}\) value is calculated as \(r_{AC_{sim}} = \frac{AC_{sim}}{AC_{limit}}\), for all occupants selected, except for those where the assessment model is the same as the selected test model. In this example, it is only calculated for M1. Appropriate hover text is available for cells where \(r_{AC_{sim}}\) was not calculated, and 'N/A' is displayed for such cells.
- According to equation 4, the \(r_{AC_{test}}\) value is calculated as \(r_{AC_{test}} = \frac{AC_{test}}{AC_{limit}}\), for all occupants. The model selected in the Select test model combo box will be used as the test model. The \(r_{AC_{test}}\) cells will have hover text displaying the Assessment Criteria Limit value for that particular assessment, as specified in Table 7 of the Euro NCAP VTC protocol.
- According to equation 5, the \(d_{AC}\) value is calculated as \(d_{AC} = \left| r_{AC\text{ test}} - r_{AC\text{ sim}} \right| \). The \(d_{AC}\) values will only be calculated if the \(r_{AC_{sim}}\) is calculated and \(r_{AC\text{ test}} \geq 50\%\). If calculated, appropriate hover text will be added to the cell, and the cell will be colour-coded to indicate if that assessment meets Validation Criterion 2.
The deviations between the ratios must be < 30% for each considered assessment criteria to fulfill the validation criterion 2.
Table 7 of the Euro NCAP Virtual Far Side Simulation & Assessment Protocol lists all the assessment types which must be fulfilled for VC2, along with their respective lower performance limit (\({AC_{limit}}\)) values.
Head excursion
One of the assessment types required for Validation Criterion 2 is head excursion, as specified in Table 7.
To plot the head excursion curve, select the DRIVER_HEAD_EXCURSION assessment type as shown in the image below.
A few inputs are required for this assessment:
- Distance between head CoG and Orange line (mm): This is pre-filled with value equal to (2 * abs(head y coordinate)), based on simulation model data, with the assumption that seats are positioned symmetrically along the vehicle centreline. If the default values are not correct, then you can edit them.
- Distance between head Cog and Red line (mm): The red line marks the maximum post-physical-test intrusion of the interior door panel. We have arbitrarily pre-filled a default value of (2 * abs(head y coordinate) + 125), based on simulation model data. Please adjust the value to match the intrusion from your physical tests.
- Countermeasure: The maximum head excursion score that can be obtained when in the red zone depends upon whether the vehicle is equipped with a countermeasure or not. The default state of the checkbox is set based on whether an Airbag structure (countermeasure) is defined in user data.
Calculation of Validation Criterion 2 ratios is a bit different for the DRIVER_HEAD_EXCURSION assessment compared to other assessment types described above.
DRIVER_HEAD_EXCURSION curves for Euro NCAP start with an 80 mm offset, as can be seen in the graph below, to account for the distance between the head CoG and the outer part of the head, to obtain the maximum head excursion. For example, considering this 80 mm offset, the maximum head excursion \(d_{Hmax}\) for models M1 and T1 is 639.97 mm and 794.576 mm, respectively, as shown in the graph below.
To calculate the \(r_{AC_{sim}}\) and \(r_{AC_{test}}\), we internally reduce the head excursion value by 80 mm, then divide the result by the \({AC_{limit}}\) value. This differs from the approach used for other assessment types, where the assessment value is simply divided by the limit. This adjustment is necessary because the calculation of the\({AC_{limit}}\) for head excursion requires subtracting 80 mm from the distance between the head CoG and the orange line (770.34 mm for this case), as specified in Table 7. To ensure consistency and to work with comparable quantities, we also subtract 80 mm from the head excursion value before dividing it with the \({AC_{limit}}\).
Thus, the \(r_{AC_{sim}}\) for the M1 model will be:
\(\frac{d_{Hmax} - 80}{AC_{limit}} = \frac{639.97 - 80}{770.34 - 80} = 0.811151\)
And the \(r_{AC_{test}}\) for the M1 model will be:
\(\frac{d_{Hmax} - 80}{AC_{limit}} = \frac{794.576 - 80}{770.34 - 80} = 1.03511\)
Head excursion/offset curve for C-NCAP Far Side Occupant Protection
The head offset curve for C-NCAP Far Side Occupant Protection is extracted from the position at the front endpoint of the circular hole at the top of the head, as specified in Appendix H.1.2.1.3.3 of the C-NCAP Management Regulation (2024 Edition). Consequently, the DRIVER_HEAD_EXCURSION curve starts at an offset, as shown in the graph below:
An option to specify which node to use for extracting the curve is provided in the Automotive Assessments Occupant panel in PRIMER. You may need to create the *DATABASE_HISTORY_NODE keyword as it is not defined as standard in the DYNAmore PDB WorldSID dummies.