Model-free adaptive discrete-time full-order sliding mode constrained control for path following of unmanned surface vessels

Considering the dynamic uncertainty, input saturation, and the discrete characteristics of digital control, a practical path following method is proposed for unmanned surface vessels (USV). Online identification for the heading model with uncertainty is presented based on a data-driven technique. Further, a constrained full-order terminal sliding manifold is constructed based on an auxiliary system to solve the input saturation. A full-order sliding mode heading controller is designed for USV in discrete-time form and the stability analysis is provided. Additionally, integral line of sight (ILOS) guidance law is introduced to generate the desired signal for the path following of USV. Simulations and experiments show that the proposed method is effective to realize tracking the desired path and has better performance than the existing popular method.