Novel Approach for Predicting Steering Rack Load Using Multibody Simulation

In the initial stages of a vehicle development program, the sizing of various components is a critical deliverable. The steering system, in particular, requires a precise estimation of the rack load for the appropriate sizing of the rack and assist units. Accurately predicting the load on the system during the early stages of development is challenging, especially in the absence of benchmark or legacy data. Commonly used processes for estimating parking steering effort often employ simplistic approaches that may fail to account for parameters such as tire size, vertical stiffness, and steering geometry, leading to reduced accuracy. This paper introduces an advanced methodology for predicting steering rack loads, which incorporates considerations such as contact patch size and pressure variation, as well as the tire jacking effect. The methodology involves mathematical modeling of the contact patch using mesh-grids, utilizing common inputs available in the early stages of vehicle development, such as tire size, tire vertical stiffness, front axle weight, and suspension geometry variations. This approach aims to reduce development time while enhancing accuracy. The predicted results have been found to closely align with physical measurements. The findings indicate that the proposed methodology significantly improves the precision of steering rack load predictions, thereby facilitating the design of more resilient and efficient steering systems.