Fuzzy Robust Adaptive Control Scheme For Trajectory Tracking Of An Unmanned Surface Vehicle

Unmanned surface vehicles are the marine intelligent motion platform, which process many excellent characteristics, e.g.,small volume, favorable invisibility, high sensitivity and no casualties, such that autonomous sailing and more complex maritime operations tasks can be independently and efficiently achieved with more attentions by most countries. Currently, trajectory tracking control is a significant research of unmanned surface vehicles, which is treated as the basis of achieving autonomous sailing.Unmanned surface vehicle systems with complex nonlinearity and uncertainties are easily disturbed by the external environment such that trajectory tracking of them has been becoming a challengeable control issue. With the increasing development of control theorems, the model-based adaptive control schemes are not able to meet the requirement of the increasing on the control accuracy. Therefore, this paper proposes a fuzzy robust adaptive control scheme for trajectory tracking of unmanned surface vehicles without system model.Firstly, to cope with the trajectory tracking control of unmanned surface vehicles in the presence of constant disturbances, considering the unmanned surface vehicles dynamic model with Coriolis matrix and damping term, a trajectory tracking control of unmanned surface vehicles based on backstepping design technique and Lyapunov stability theorem is proposed by using the system tracking error dynamics, and the effectiveness is verified by simulation results.Moreover, an adaptive fuzzy trajectory tracking control scheme for the unmanned surface vehicles with parameter uncertainties and unknown time-varying disturbances is proposed. Specifically, the unknown nonlinear term and external disturbances are approximated by the fuzzy logic system, the control law and adaptation laws for adjusted parameters are derived by the combination of backstepping design technique and Lyapunov stability theorem which guarantees the stability of closed-loop system and the convergence and boundedness of the adaptive parameters.Simulation results demonstrate the effectiveness and superiority of the proposed scheme.Finally, a variable universe adaptive fuzzy control scheme with scaling factor to handle with contradiction between control accuracy of fuzzy logic system and fuzzy rules such that the higher accuracy can be obtained by using less fuzzy rules. The proposed scheme combining backstepping design technique introduce a integrated robust term to compensate the system approximation error to achieve trajectory tracking of unmanned surface vehicles with high accuracy. In addition, the effectiveness and superiority of the proposed scheme are confirmed by simulation results.