Overview
ISO 11026:2010 - Heavy commercial vehicles and buses - Test method for roll stability - Closing-curve test - is an open‑loop vehicle dynamics test standard that specifies how to measure roll stability for heavy commercial vehicles and buses negotiating a curve on a dry surface. It applies to vehicles defined in ISO 3833 (categories M3, N2, N3, O3, O4) and is intended primarily for vehicles equipped with electronic roll stability control systems. The method produces repeatable, discriminatory data on how vehicles respond to a path of constantly increasing curvature (a closing‑curve).
Key topics and requirements
- Test principle: Start from straight‑line driving at constant longitudinal velocity and steer onto a closing curve defined by a constant jerk (rate of change of lateral acceleration).
- Path definition: Curvature and path coordinates are defined mathematically so the path transition produces a constant jerk at constant speed.
- Measured variables: Mandatory measurements include longitudinal velocity (Vx), lateral acceleration (ay), ESC intervention indication, and indicators of roll or yaw instability (outriggers/anti‑jackknife). Recommended measurements include steering angle, yaw rate, articulation angles, wheel speeds, brake pressures, and wheel slip.
- Test conditions: Dry surface, specified loading (standard: maximum loading with the center of gravity high enough to cause rollover if stability control were disabled), and safety measures (anti‑rollover outriggers, anti‑jackknife devices).
- Measuring equipment: Instrumentation, transducer installation and data processing per ISO 15037‑2.
- Data evaluation:
- Average jerk is computed from lateral acceleration after the first 1 m/s² occurrence and before ESC intervention by linear fit.
- Validity criteria: average jerk within ±10% of intended value; vehicle path deviation ≤ ±0.5 m; longitudinal velocity variation ≤ ±5% prior to ESC intervention.
- Characteristic outputs: roll/yaw stability outcome, lateral acceleration and speed at ESC intervention; in series tests, the minimum average jerk causing roll instability.
Applications and users
ISO 11026 is used by:
- Vehicle manufacturers and OEMs for design validation of chassis, suspension and electronic roll stability systems.
- ADAS and ESC suppliers for system tuning and performance verification.
- Independent test laboratories and certification bodies performing stability testing.
- R&D teams studying rollover prevention, vehicle dynamics and safety countermeasures.
- Regulators and safety analysts evaluating test-based evidence (with caution - standard notes that correlation with accident statistics is required before regulatory use).
Related standards
- ISO 15037‑2: Vehicle dynamics test methods - General conditions for heavy vehicles and buses (measuring equipment)
- ISO 3833: Road vehicles - Types - Terms and definitions
- ISO 8855: Vehicle dynamics vocabulary
Keywords: ISO 11026, roll stability, closing‑curve test, heavy commercial vehicles, buses, electronic roll stability control, vehicle dynamics, jerk, lateral acceleration.
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