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Vehicle Test Object Modelling Documents Validation

Explore methods for validating vehicle test object modelling documents, focusing on time histories and comparison techniques. Address research gaps and challenges in validation procedures for systems certification. Consider statistical analysis and key performance metrics.

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Vehicle Test Object Modelling Documents Validation

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  1. Time Frame • CM/E finalised the vehicle and test object modelling documents (Parts 2&3) • These documents should be revised at regular intervals • Validation procedures still require research • Further analysis of the Round Robin data in ROBUST is a necessary input • Difficult to predict the delivery of a draft procedure – possibly 2007 1 NCHRP_22_24 January 22 2007

  2. Validation. • If we want to use CM for the certification of a system which are the requirements for a “validated” model? • Validation should be based on a comparison between test and simulation using: • Severity indices. • Barrier performance: • Deformation. • Failures. • Vehicle trajectories. • Vehicle time histories (acceleration yaw ratio …) • ….. • Validation methods MUST be able to validate also tests repetition. 2 NCHRP_22_24 January 22 2007

  3. Validation • The problem is how to define an objective procedure to compare time histories. • Direct comparison between avcceleration has been already demonstrated to be not applicable. Is not possible to find an objective way to compare such different curves. • Other approaches: • Statistical approach (Chalmers software). • Velocity. • Chalmers software: • Statistical comparison between a master and a signal to be tested. • The comparison is based on 8 statistical indices. 3 NCHRP_22_24 January 22 2007

  4. CFC 60 • 3 over 8. We could relax the limits. But with no statistical meaning. 4 NCHRP_22_24 January 22 2007

  5. Filtered at 12.5 hz • Always 3 over 8 5 NCHRP_22_24 January 22 2007

  6. Different experimental test • Worse condition. Different requirements in the second phase? 6 NCHRP_22_24 January 22 2007

  7. Only the first phase.Always the same problem. • Minimum peak fails even if is less important. 7 NCHRP_22_24 January 22 2007

  8. First phase. • Only way to pass all the tests. • First part of the impact and relaxation of limits. 8 NCHRP_22_24 January 22 2007

  9. Two experimental tests • 4 over 8! 9 NCHRP_22_24 January 22 2007

  10. Other possibility • Window obtained from test where simulation must be contained. • Not easy to justify a window (delta time, delta g, filtering) 10 NCHRP_22_24 January 22 2007

  11. Other possibilty 3.Final consideration • Compare two velocity time histories (experimental and numerical). • If the difference between these two time histories become greather than X(t)% your model is validated until this time. • After this time your model is not validated. • We are applying this approach also to the deformable barrier and to other impacts 11 NCHRP_22_24 January 22 2007

  12. Validation. • Comparison based on local velocity components. • Reference frame is not inertial. • Accelerations evaluated on a reference system “mounted” on the vehicle. • To proper evaluation of velocity relative mechanics should be used. • Comparison based on global velocity components. • Planar motion. • Need of yaw rotation (not filtered). • Evaluation of global components of velocity (interpretation less immediate) 12 NCHRP_22_24 January 22 2007

  13. Vehicle rotation X X X X α α α x y x x x Y y y y Vy Local Vy Global 13 NCHRP_22_24 January 22 2007

  14. Round Robin. • Rigida barrier h=800 mm. • Tb11 • 900 kg • 20° 14 NCHRP_22_24 January 22 2007

  15. Round Robin 1. Same new vehicle. Only exp. results 15 NCHRP_22_24 January 22 2007

  16. Round Robin 2 • Different not new vehicles 16 NCHRP_22_24 January 22 2007

  17. Robust 4.3 • Two more tests on RR1 17 NCHRP_22_24 January 22 2007

  18. All the tests. • Same rigid barrier. • Different vehicles. • 12 nominally identical. 18 NCHRP_22_24 January 22 2007

  19. Round Robin. Test and simulation • Not so bad. • Friction influence. (Not understood from acceleration comparison). 19 NCHRP_22_24 January 22 2007

  20. Rigid barrier results • Components • Vy global: good agreement between tests • Vx global: scatter between tests (exit velocity is different) • Vz global: less significative. • Seems to work. 20 NCHRP_22_24 January 22 2007

  21. Deformable barrier. • Task 4.1 Robust. • N2 barrier (max 1500 kg 110 km/h 20°). • Different vehicles. • Gorund differences. 21 NCHRP_22_24 January 22 2007

  22. Yaw angle X X X X α α α x y x x x Y y y y Angle 22 NCHRP_22_24 January 22 2007

  23. Yaw angle problems during tests 23 NCHRP_22_24 January 22 2007

  24. Comparison. 24 NCHRP_22_24 January 22 2007

  25. Comparison 1 • Dynamic deflection (ground) • Curve 1 (blue)=0.9m • Curve 3 (red)=0.7m • Difference 25% 25 NCHRP_22_24 January 22 2007

  26. Tests and simulation 26 NCHRP_22_24 January 22 2007

  27. Conclusion • From Round Robin encouraging results. • From deformable barrier results not acceptable. • Problem: • With these results (deformable) window to accept simulation is too wide. • According to 1317 these tests are equivalent. Means that a simulation with these differences is validated? 27 NCHRP_22_24 January 22 2007

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