Distance-Based Adaptive Inflation Control for External Automotive Airbags

External automotive airbags are a promising pre-crash countermeasure, yet most concepts deploy to a fixed pressure that may be unnecessarily stiff at larger stand-off distances. This paper proposes a distance-based staged inflation schedule in which the commanded internal pressure is mapped to obstacle distance using thresholds at 2.0 m, 1.0 m, and 0.5 m. The schedule commands 130 kPa, 170 kPa, and 200 kPa, respectively, while maintaining ambient pressure (101.3 kPa) for distances greater than 2.0 m. A control-oriented parametric evaluation over 5.0 m to 0 m with 0.5 m discretisation shows that, relative to a fixed-pressure baseline (220 kPa), the commanded pressure is reduced by 54% at 5.0 m and remains lower across most of the approach while reaching 200 kPa in the near field for structural support. The analysis is limited to commanded pressure scheduling and a first-order stiffness proxy; contact mechanics, injury metrics, and experimental validation are identified as next steps. A deterministic distance-indexed three-stage schedule commands external airbag pressure from ambient to 200 kPa as stand-off distance reduces from 5 m to contact, reducing commanded pressure versus a fixed-pressure baseline across most of the approach.