Adaptive fuzzy reaching law tracking control of uncertain fully-actuated underwater vehicles with system uncertainties and unknown disturbances

In this paper, an adaptive fuzzy reaching law controller (AFRLC) for robust tracking control of uncertain full-actuated underwater vehicles (FAUV) in the presence of system uncertainties and unknown external disturbances is investigated, where a novel reaching law controller is constructed with a variable speed structure of system states such that the chattering phenomenon in traditional reaching law can be reduced. Moreover, a fuzzy uncertainty observer is employed to online observe the system uncertainties and it is incorporated into the sliding-mode reaching law. Theoretical analysis proves that the proposed AFRLC can ensure the stability of underwater vehicles tracking system and all signals in the closed-loop control system are uniformly ultimately bounded. In addition, the observation error can asymptotically converge to zero. Simulation results demonstrate the effectiveness of the proposed control scheme.