Analyzing Rollover Indices for Critical Truck Maneuvers
Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming
a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a
system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually
performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated
based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in
different situations.
In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8×4
twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel
dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped
turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as
minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit
of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal
maneuvers with different rollover indices, thus limiting the vehicle's maneuvering envelope with respect to each rollover index. The
resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the
conservativeness of the indices for assessing the risk of rollovers are discussed.
Kristoffer Lundahl, Chih Lee, Erik Frisk and Lars Nielsen
SAE International Journal of Commercial Vehicles,
2015
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