tracking control of underwater vehicles based on adaptive nonlinear robust inner/outer loop approach

Highly nonlinear systems with parametric uncertainties and external disturbances deteriorate the tracking control performance of autonomous underwater vehicles. in this research, to attain- optimal precision, an adaptive integral-type terminal sliding mode controller is proposed. to this end, the kinematics and kinetics controller laws are developed as the outer and inner loop control to track desired trajectories. the kinematics controller, as the outer controller, is developed to control the position errors. the kinetics controller, as the inner servo loop, is developed based on the system dynamics model and an adaptive integral-exponential sliding surface to control the internal velocity errors. in order to enhance the control proficiency, we have implemented an adaptive switching rule within the kinetic control algorithm, enabling an automated adjustment of all controller parameters. therefore, the increase and decrease of these switching parameters will occur according to the system conditions, while its stability is guaranteed using lyapunov theorems. the obtained results show the merits of the proposed controller in terms of high accuracy performance and low computation cost for real-time implementations.