On the steering of automated vehicles: Theory and experiment

Several facets of the automatic lateral control of individual ground vehicles are considered in detail. First, a path-dependent coordinate system for describing vehicle motion is defined, and the availability of motion quantities for control purposes is specified. Second, the lateral dynamics of a typical U.S. passenger sedan are empirically obtained and validated with data from full-scale studies. Third, various designs, in which different types of compensation are employed, are evaluated in terms of specified requirements and attractive candidates are specified. Finally, several controller designs were tested under full-scale conditions wherein a wire-reference configuration and a dual-mode test vehicle were employed. The latter was automatically steered on both straight and curving roads at speeds up to 35.8 m/s (80 mph). In one typical case, the maximum tracking error observed was 0.0635 m and occurred both when a sidewind was present and when the vehicle entered a curving section of roadway. Excellent lateral control-close tracking, good insensitivity to disturbance forces, and a comfortable ride-can be obtained using a relatively simple controller.