Design of Sliding Mode Autopilot with Steady-state Error Elimination for Autonomous Underwater Vehicles

Autonomous Underwater Vehicles (AUVs) have nonlinear and time-varying behaviour and unmodelled dynamics. This paper describes the design, development and evaluation of nonlinear sliding mode autopilot system for an AUV to control the speed, steering and depth of the nonlinear AUV. It has also been observed by some researchers that the sliding mode controller is unable to eliminate the steady-state error. A method of eliminating the steady-state error associated with the sliding mode controller has been proposed in this paper. In addition,\ud performances of the sliding mode autopilot were evaluated by\ud simulation on the nonlinear model of the AUV over a variety\ud of operating conditions. The robustness of the control system was evaluated in the presence of disturbances and parameter uncertainties.\u