Analysis of lateral dynamics of a human steered vehicle and its application to the optimal four-wheel steering system

A method to study the handling characteristics of a vehicle moving along a curved path is presented. A simple bicycle model and a feedback controller with proportional gain are used to simulate the vehicle and the driver. The lateral stability of the vehicle-driver system is analyzed by using the root locus method and numerical integration in the time domain. The effect of the curvature on the system stability is discussed in detail. A new suggestion is made for the look ahead distance to calculate the preview lateral error of the vehicle with respect to the center of the road. Interesting results are shown for some important parameters such as the gain factor, the vehicle speed and the curvature of the path. Possible extensions of the method to more general cases and other applications are discussed.; Various methods to design the four wheel steering system (4WS) are discussed. The vehicle is modeled as a closed loop system using a bicycle model with a human controller and a rear wheel steering scheme. General formulation of the system equation is made using the state space form. An optimal control algorithm is developed using a linear quadratic regulator model. Three optimal control schemes with different performance indices are analyzed and compared in terms of handling responses. Two simple feedback control 4WS systems are suggested as alternatives of the optimal control 4WS system. The systems are essentially variations of the existing vehicle speed function based (VSF) system. They utilize information from the system stability analysis and the results of optimal control system simulations. Numerical simulation shows that the new systems show better performance than the existing VSF system.