  Cooperative vehicle management emerges as a promising solution to improve
road traffic safety and efficiency. This paper addresses the speed planning
problem for connected and autonomous vehicles (CAVs) at an unsignalized
intersection with consideration of turning maneuvers. The problem is approached
by a hierarchical centralized coordination scheme that successively optimizes
the crossing order and velocity trajectories of a group of vehicles so as to
minimize their total energy consumption and travel time required to pass the
intersection. For an accurate estimate of the energy consumption of each CAV,
the vehicle modeling framework in this paper captures 1) friction losses that
affect longitudinal vehicle dynamics, and 2) the powertrain of each CAV in line
with a battery-electric architecture. It is shown that the underlying
optimization problem subject to safety constraints for powertrain operation,
cornering and collision avoidance, after convexification and relaxation in some
aspects can be formulated as two second-order cone programs, which ensures a
rapid solution search and a unique global optimum. Simulation case studies are
provided showing the tightness of the convex relaxation bounds, the overall
effectiveness of the proposed approach, and its advantages over a benchmark
solution invoking the widely used first-in-first-out policy. The investigation
of Pareto optimal solutions for the two objectives (travel time and energy
consumption) highlights the importance of optimizing their trade-off, as small
compromises in travel time could produce significant energy savings.
