Safe and sub-optimal CAV platoon longitudinal control protocol accounting for state constraints and uncertain vehicle dynamics

Abstract

State constraints and uncertain vehicle dynamics severely affect control stability and performance of connected and autonomous vehicle (CAV). To this end, this study puts forward a safe and sub-optimal longitudinal control protocol for CAV platoon with uncertain vehicle dynamics and state constraints. For platoon leader, a second order disturbance observer with L2 stability is presented to estimate lumped uncertainty coupled in vehicle dynamics. By iteratively utilizing control barrier functions and control Lyapunov function, state constraints and speed trajectory tracking stability condition are encoded into control constraints. Based on disturbance observer and encoded constraints, an extended quadratic programming is established as trajectory control law for platoon leader. For platoon followers, backstepping method and disturbance observer accounting for forward communication network are synthesized as formation control law. Besides, conditions of individual vehicle stability and string stability for formation control law are analyzed. Simulation results show that the leader of platoon can automatically switch its drive mode between speed cruising and safe headway keeping, respectively. Furthermore, each follower in platoon can follow its predecessors coordinatively and precisely.