A mechanical integral steering system for increasing the stability and handling of motor vehicles

Abstract

The article deals with the design, modeling, and simulation of an innovative four-wheel steering system for motor vehicles. The study is focused on the steering box of the rear wheels, which is a cam-based mechanism, while the front steering system uses a classical pinion—rack gearbox. In the proposed concept, the four-wheel steering aims to improve the vehicle stability and handling performances by considering the integral steering law, which is formulated in terms of correlation between the steering angles of the front and rear wheels. In this regard, a double-profiled cam is designed, in correlation with the input motion law applied to the steering wheel. The cam profile dictates (prescribes) the translational movement of the rear follower, which is connected to the left and right steering tierods, turning—as appropriate—the rear wheels in the same direction (for stability) or in opposite (for handling) to the front wheels. The cam-based mechanism is able to carry out complex motion laws, providing accurate integral steering law. The dynamic modeling and simulation of the four-wheel steering vehicle was performed by using the Multi-Body Systems package Automatic Dynamic Analysis of Mechanical Systems of MSC.Software, the full-vehicle model containing also the front and rear wheels suspension systems, as well the vehicle chassis (car body). The dynamic simulations in virtual environment have resulted in important results that demonstrate the handling and stability performances of the proposed four-wheel steering system by reference to a classical two-wheel steering vehicle.