Virtual car following based cooperative control of connected automated vehicles in complex scenarios: A roundabout example

This paper proposes a generic cooperative control framework for connected and automated vehicles (CAVs) for compound maneuvers of car-following, merging, and diverging on curved paths. The proposed framework is illustrated through a roundabout example. The framework is based on the “virtual car-following” concept, where multiple conflicting streams of CAVs are transformed onto a single, straight virtual axis. With this transformation, the control of compound maneuvers is simplified into a car-following and lane-keeping control problem. This is facilitated by firstly applying curvilinear coordinates to each approach to transform the vehicle kinematic motions along a curved path into longitudinal and lateral movements on a straight path. Then the transformed paths for all the conflicting vehicle streams are rotated onto the same virtual axis with respect to the merging/diverging point to form a virtual car-following stream. Traffic conflicts are then resolved through virtual car-following control, paired with lane-keeping control. Specifically, a serial distributed model predictive control (MPC) with a time-varying horizon is designed to fulfill these control tasks simultaneously. Numerical simulations are conducted for a single-lane roundabout scenario. The results showed that the proposed strategy is capable of actively generating gaps for vehicles to safely merge, reducing voids, and dampening traffic disturbances as manifested by speed variations.