Lateral and longitudinal vehicle control coupling for automated vehicle operation

This paper covers developments in the control integration part of the automated highway system (AHS) program of the California Partners for Advanced Transportation and Highways (PATH). The control integration project investigates the potential for improving controller performance through an integrated design of a combined steering and speed controller specifically designed to address the coupling between the steering and speed controls. The following results are presented: (1) the identification and characterization of the various coupling effects through an analysis of vehicle dynamics; (2) the design of a combined controller which compensates for the coupling effects; and, (3) the evaluation of the improvements contributed by the coupling compensation through simulations and through experiments on full-scale test vehicles. Sliding control and dynamic surface control (DSC) methods are used to facilitate the inclusion of the complex, nonlinear coupling effects in the controller derivation. A multiple-rate observer is designed to obtain a lateral velocity estimate which is essential to the implementation of the controller on the test vehicle. Simulations and experiments show that the coupling compensation does improve controller performance and that the combined controller is robust to modeling imperfections and vehicle parameter variations. The combined controller described in this paper may be the ideal basis for future implementation of the automated highway system.