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Simulation of the Steering System Power Demand during the Concept Phase Focusing on Tire Modelling at Standstill
Abstract:
Estimating the power demand of a steering system is one of the main tasks during
steering system development in the concept phase of a vehicle development
process. Most critical for typical axle kinematics are parking maneuvers with
simultaneously high rack forces and velocities. Therefore, the focus of the
article is a tire model for standstill, which can be parametrized without
measurements, only having tire dimensions and conditions (inflation pressure and
wheel load) as input. Combined with a double-track model, a vehicle model is
developed, which is able to predict the rack force and is fully applicable
during the concept phase.
The article demonstrates quantitatively that the tie rod forces, and thereby
especially the tire bore torque, cause the largest fraction of the power demand
at the rack. For this reason, the prediction of the bore torque is investigated
in detail, whereby basic approaches from the literature are analyzed and
enhanced. Furthermore, an approach is derived for considering the influence of
horizontal forces in the tire contact patch on the bore torque. The development
of the tire model is supported by a tire data basis with approximately 900
measured tire configurations. Finally, two test vehicles are used to validate
the vehicle model successfully.