Overview
ISO/TS 18571:2024 - Road vehicles - Objective rating metric for non-ambiguous signals - defines a standardized, objective metric and rating procedures to quantify the level of correlation between time‑history signals from physical tests and computational models. Focused on vehicle safety applications, the Technical Specification supports model validation by comparing non‑ambiguous signals (e.g., forces, moments, accelerations) and provides validated procedures, score components and preprocessing guidance. The document also contains informative case studies (Annex A).
Key topics and technical requirements
- Purpose: Provide validation metrics and procedures for objective comparison of CAE and test signals in road vehicle safety.
- Metric components:
- Corridor score - evaluates how the model signal stays within tolerance corridors around the reference signal.
- Phase score - quantifies timing (time‑shift) differences between signals.
- Magnitude score - measures amplitude agreement between signals.
- Slope score - assesses agreement of derivative / rate‑of‑change behavior (new algorithm uses a nine‑point moving average to smooth slopes).
- Overall ISO rating: Combines the component scores into a single, interpretable rating.
- Pre‑processing requirements:
- Synchronization of signals, appropriate sampling rate, and filtering (smoothing) prior to scoring.
- Guidance on interval of evaluation and handling multiple responses.
- Algorithmic notes:
- Revisions in the 2024 edition include expanded guidance on window size for Dynamic Time Warping (DTW) (recommended ~10% of data length) and improvements to slope scoring.
- Limitations: The specification documents signal types within scope and provides caveats on metric interpretation and validation boundaries.
Practical applications
- Model validation in CAE workflows for crash, impact and occupant safety simulations.
- Objective assessment of component or subsystem dynamic responses (forces, accelerations, moments).
- Verification of simulation fidelity during design iterations and regulatory or supplier exchanges.
- Use in correlation reports, design reviews, and to justify model predictive capability for safety decisions.
Who should use this standard
- CAE engineers and model validation specialists in the automotive industry
- Vehicle safety test laboratories and OEM validation teams
- Simulation analysts comparing test and model time‑history outputs
- Researchers and standards developers working on objective signal comparison
Related standards
- ISO/TR 16250 (contextual background on model validation methods)
- References and related guidance from CAE/validation communities (AIAA, ASME, DMSO) are noted in the introduction for broader model validation practices.
Keywords: ISO/TS 18571:2024, objective rating metric, non‑ambiguous signals, road vehicles, model validation, CAE, time‑history signals, corridor score, phase score, magnitude score, slope score, dynamic time warping.