Switching from autopilot to the driver: a transient performance analysis

One of the main safety concerns associated with semi-autonomous vehicles is the sharing of control between a human driver and an autonomous driving system. Even with an attentive driver, such switches in control may pose a threat to the safety of the driver and the surrounding vehicles. The aim of this study is to develop an indicator that can measure the level of safety during a driver take-over, using knowledge about the system known a priori. A model-based approach is used to analyse the system with special focus on the lateral dynamics of the vehicle. The driver and the vehicle are modelled as linear systems, and a path tracking controller is used to serve as an autonomous system. With this structure, shared control is studied as a switched system, in which the vehicle’s lateral control switches between the autonomous system and the driver. A bound on the transient dynamics that arise due to a switch is derived, using the induced L _∞ norm. This bound is then used to formulate an indicator that checks if the states/outputs of interest are within acceptable limits. A comparison with simulation results has shown that the indicator successfully captures the effect of different system parameters on take-over safety, although in a slightly conservative manner. This indicator can be further developed as a tool to be used in the design and evaluation of shared-/multi-modal control systems in future vehicles.