Reference Models of 4WS Vehicle Lateral Dynamics for the Synthesis of Steering Algorithms

The presented paper describes selected reference models describing the kinematics and dynamics of four-wheel steering (4WS) vehicle motion in a plane of the road. These models are based on well known “bicycle model” (two second order linear differential equations) supplemented by non-linear equations of trigonometric transformation of variables from local to global coordinate system. After linearization and Laplace transformation, these models acquire the forms of transfer functions which, as shown in computational examples presented in the paper, greatly facilitates the analysis of vehicle motion, as well as the synthesis of control algorithms. Especially, transmittance form of the reference models facilitate sensitivity analysis of vehicle lateral dynamics and steering system algorithms, because their parameters are analytical functions of “mechanical” parameters. For synthesis of steering system algorithms which should be adequately effective for on-line computations, the transfer functions can be reduced in several ways. One of them is discussed in the paper.