Design and Simulation of an Integrated Steering System for All-purpose Sport Utility Vehicles (SUVs) – Case for Toyota

Abstract

Sport Utility Vehicles (SUVs) have the largest (and growing) global market share for passenger cars, despite having a generally higher rollover propensity, lower maneuverability and poorer fuel economy than other passenger vehicle segments. These are consequences of longer wheelbase, wider track and higher center of gravity. Stability and agility depend heavily on steering systems. This paper involves the design and simulation of an integrated steering system for SUVs, case for Toyota. In the spirit of Kaizen, the paper explores possible improvements on SUV handling characteristics in an energy-efficient manner. A detailed literature review investigated the existing systems on the Toyota Fortuner AN160 as the benchmark vehicle for the research, as well as systems on vehicles with related steering and suspension geometries. Inspired by the remarkable stability of cheetahs in high-speed maneuvers, cheetah dynamics (biomimicry) were translated to the desired solution as four-wheel steering (4WS). Consulting with Toyota Zimbabwe, concepts were generated and detailed designs for the rear-wheel steering axle geometry and its actuation were done as the first design phase. A novel system to combine Toyota’s Variable Gear Ratio Steering (VGRS) system with Electric Power Steering (EPS) on a single electric motor was also conceptualized and detailed design shall be carried out for this system as the second design phase, with exhaustive experimentation. Theoretical design of the axle assembly parts was confirmed by static simulations for design correction and weight optimization. Finally, costing, sustainability and impact analyses of the design were carried out. Three key outcomes of this paper are improved vehicle handling, sustainable steering system development and better compliance with the next major step in automobile evolution – autonomous driving.