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Driver Adaptation to Changes in Automobile Handling Properties

August, 2015

Automobile drivers frequently encounter changes in vehicle handling properties that require them to adjust their steering control actions. These changes may be benign, such as slightly different steering ratios in different cars, or potentially life-threatening, such as suddenly encountering a patch of black ice on the roadway. Understanding how drivers adapt to such handling changes is important for informing the design of new driver assistance systems and training methods. Although adaptation has been studied extensively in the laboratory for applications such as arm reaching and walking, there are still many unanswered questions about the adaptation process in the context of driving. This dissertation addresses the need to understand how drivers adapt to handling changes by designing and implementing a novel user study with an experimental vehicle. Drivers complete several trials of a lane change task while the vehicle handling properties are mod- ified in one of four ways that represent scenarios similar either to common laboratory ex- periments from arm reaching studies or to real-world situations specific to driving. The specific handling changes are (1) scaling the steering ratio, (2) reversing the steering direc- tion, (3) scaling the steering wheel torque, and (4) simulating low friction vehicle dynamics. To enable the latter type of handling change, a new approach to handling modification has been developed using online simulation of the dynamics and tire forces of a reference vehicle model. The resulting control scheme provides a method of emulating a range of planar vehicle dynamics, in particular those of a vehicle traveling on an icy road. The results of user studies with the four handling modifications demonstrate that adaptation exists in automobile steering control tasks. The studies provide evidence that drivers adapt their steering control based on steering wheel angle, not on steering wheel torque. Finally, individual driving style influences the degree of adaptation necessary when encountering a low friction surface.