Simulation of optimal integral sliding mode controller for the depth control of AUV

The depth control problem is described and addressed for a small autonomous underwater vehicle in this paper. Based on the nonlinear model of AUV in vertical plane, the paper established a mathematical model of AUV´s depth motion in vertical plane by linearizing the model at a specified operating point. An optimal integral-sliding-mode controller was designed for the AUV depth control system by constructing a sliding mode surface with quadratic optimization. And a saturation function was introduced to reduce system chatting. The results of simulation demonstrated that this proposed controller was effective to eliminate the disturbances caused by AUV´s nonlinear and model uncertainty. Meanwhile the system showed a better performance both in speedness and robustness compared than a PID controller.