Adaptive Fuzzy Sliding Mode Control with Extended State Observer for ROV Trajectory Tracking

Abstract

This paper addresses the horizontal-plane trajectory tracking problem of a small remotely operated vehicle (ROV) in the presence of unknown disturbances and input saturation. A three-degree-of-freedom dynamic model, including surge, sway, and yaw motions, is first established. On this basis, an extended state observer (ESO) based adaptive fuzzy nonlinear integral sliding mode controller (AF-NISMC), denoted as the ESO-AF-NISMC method, is developed to enhance disturbance rejection while alleviating the chattering commonly associated with the traditional sliding mode control. The ESO is used to estimate the lumped disturbance in real time and introduce corresponding feedforward compensation. Meanwhile, the adaptive fuzzy switching mechanism adjusts the switching gain according to the evolution of the sliding surface, thereby improving the balance between robustness and control smoothness. MATLAB simulations are carried out under several challenging conditions, including time-varying disturbances, sudden lateral and yaw perturbations, actuator lag, and saturated control inputs. Compared with the traditional integral sliding mode control (ISMC), the proposed method decreases the posttransient position RMSE from 20.292 mm to 2.834 mm and the yaw RMSE from 1.225 deg to 0.213 deg. In addition, the chattering index is reduced from 112.81 to 81.677. These results indicate that the proposed method achieves higher tracking accuracy and smoother control performance.