Does Shared Mode Improve Steering and Vehicle Motions During Control Transition From Automated to Manual Driving in Real Passenger Car?

Drivers occasionally need to resume vehicle control when an automated driving system (ADS) cannot handle a situation. However, a lack of driver readiness can prevent a smooth transition. For example, in an obstacle avoidance situation, a method to transfer the vehicle control based on the driver's input of the steering angle can be adopted where rapid steering operation by the driver is required immediately after resuming control. It was observed from the previous studies based on a fixed-based driving simulator that the discontinuity in control due to a sudden disengagement of the control torque of the ADS resulted in steering instability. In addition, the previous studies had proposed a shared mode, in which haptic shared control (HSC) was placed between the automated and manual driving. It was demonstrated that steering stability could be improved through the shared mode. However, in the previous studies, the observation of steering instability and verification of HSC effectiveness of the shared mode were limited to fixed-based driving simulator experiments, in which there was no vehicle motion. In addition, for practical applications, a method using a torque sensor in the previous method is expected to be replaced by a more robust method, because it may introduce noise and the use of a lowpass filter leads to some time lag. Therefore, in this study, we developed a new control transition method that uses only the steering angle. We conducted experiments using a real car, in which the participants were instructed to resume steering control from the automated driving mode. The results demonstrate that the discontinuity in control during the control transition deteriorates the steering stability and vehicle motion, and the shared mode can improve them.