Fuzzy adaptive sliding mode controller for path following of an autonomous underwater vehicle

In order to reduce chattering while promoting control precision in a sliding mode control (SMC) method, a new control scheme for path following system of an under-actuated autonomous underwater vehicle (AUV) in the horizontal plane via fuzzy adaptive sliding mode control (FASMC) method was presented. A novel reaching law based on exponential reaching law and sigmoid function was proposed for sliding mode controllers of the path following system. The fuzzy adaptive controllers of boundary layers were designed based on the following errors of the AUV and the angles between the sliding surface and state vector. Compared to the SMC method, the chattering was reduced effectively and following precision was improved at the same time when the FASMC method was used. Other than that, the FASMC method maintained the robustness to the uncertainties of the mathematical models of the AUV. The results were illustrated with numerical simulations.