Design of an automatic steering controller for bus revenue service based on drivers´ steering mechanism

This paper describes an automatic steering controller based on a target and control driver steering model. Derived based on analyses of vehicle test data on the standard Double Lane Change (DLC) course, this novel target and control driver model captures driver´s key steering mechanisms. The analyses show that, instead of planning and following a desired path according to the traditional trajectory planning concept, drivers use the next lane center as the target points to generate vehicle angle error for control during lane changes. The data also suggests that drivers apply steering rate control instead of the conventional steering angle control to steer the vehicle. By extending this relatively straight-forward look-ahead based driver steering model to an automatic steering controller with a “look-down” sensing system, an equivalent controller structure was derived. The structure revealed that drivers apply a PID-type controller whose look-ahead distances and feedback gains are dependent on the vehicle speed. This equivalent controller was directly implemented on a 60-ft articulated bus for revenue service on a narrow and curving bus rapid transit line at Eugene, Oregon, USA. The field tests demonstrated that the controller achieved all the stringent performance and robustness requirements. This automated steering bus started its daily revenue service (i.e., carrying passengers) started in June, 2013.