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.