Dynamic Optimum Distributions of Lateral and Longitudinal Tire Forces in Four-Wheel Independent Steering Vehicles : Tire Force Distribution Patterns and Optimality Criteria Method(Mechanical Systems)

Abstract

Real-time optimizations of the lateral and longitudinal tire force distributions based on tire workloads are investigated. In previous studies, the authors realized minimax optimizations for several configurations of independent steering vehicles; these were realized by employing numerically robust combinations of an algebraic approach, the bisection method, and the golden section method. The purposes of this study are to investigate the applicability of optimality condition approach to minimax optimization and to consider the exploitation of complementarities between lateral forces and longitudinal forces in yaw-moment generation to further reduce the objective function. The problem for independent four-wheel steering is introduced, and the assumption of equivalent tire workload leads to a simple equation as the first optimality condition. Complementarities between the lateral and longitudinal forces provide another degree of freedom. A similar formulation and an additional optimality conditions provide stable convergence by the Newton-Raphson method. The exact optimum solution to the basic problem is obtainable by the enumeration of nine possible tire force distribution patterns.