Prescribed performance actuator-tolerance control for path following of unmanned surface vessels via the triggered adaptive line-of-sight guidance

The initial conditions beyond the prescribed region and the actuator faults are the crucial issues for the prescribed performance path following control in a low-speed harbor transportation mission. This paper proposes a new prescribed performance path following control strategy for an unmanned surface vessel (USV) by utilization of a shifting function, actuator fault-compensating technique and a triggered adaptive line-of-sight (TALOS) guidance. The main features are described as three points: (i) A TALOS guidance principle is developed on basis of the line-of-sight (LOS) guidance and the triggered strategy, leads to a discrete guidance signal, which is followed by an USV. This can reduce the calculation and transmission frequency of the guidance law. (ii) An exponential-based prescribed performance control (PPC) with consideration of a shifting function is designed to address an explicit limitation where the initial state error may exceed the prescribed boundary. (iii) The actuator faults are compensated by using the neural networks (NNs). According the former three points, the stability of the proposed algorithm is proved through the Lyapunov theorem. Finally, simulation studies are carried out via a harbor navigation mission with usage of automatic identification system (AIS) path information and a comparative example, where the effectiveness and the advantages of the proposed scheme are evaluated in presence of the external disturbances.