Platoon Formation Control of USVs With Output Tracking Error Constraints

In this paper, we investigate the platoon formation control problem for a group of unmanned surface vehicles exposed to external time-varying disturbances with output tracking error constraints, where the topology of the communication network is described by a spanning directed tree. To guarantee that the follower could preserve within the communication range between the follower and its predecessor while avoiding the collision with its predecessor, the line-of-sight (LOS) range is required to be constrained. By introducing a desired distance, the constraints on connectivity preserving and collision avoidance could be transformed into the constraints of LOS range error, i.e., the LOS range error is required to stay within a prescribed region composed of two constant bounds. To quantify the transient and steady-state performances of the orientation error and LOS range error, the tan-type barrier Lyapunov functions with exponential decaying boundary functions are employed to guarantee the satisfaction of the prescribed tracking error constraints. Since the vehicle system is exposed to the time-varying disturbances, the disturbance observers are incorporated into the controller such that the robustness of the control system is improved. Based on backstepping procedure, barrier Lyapunov functions, and disturbance observers, robust formation controller is proposed to ensure the prescribed tracking error constraints, i.e., the connectivity preserving as well as the collision avoidance constraints between the follower and its predecessor are also satisfied. Simulation results demonstrate the efficacy of the proposed control scheme.