Modeling and motion control strategy for autonomous underwater vehicles

A motion control strategy consisting of both position and speed control was designed for different work assignments of Autonomous Underwater Vehicles (AUV). To provide a form that will be suitable for simulation and control purposes, a general mathematical model of underwater vehicles was derived based on the six degrees of freedom nonlinear equations of motion. An improved S-surface controller based on capacitor plate model was introduced and optimized by a self-adapting manner to compensate the constant environmental forces for position control. The stability of speed control law was demonstrated by Lyapunov function. The simulation results show that the self-adaption can effectively diminish the steady state error for the accurate position-keeping, and the proposed mathematical model can provide an efficient test tool for the simulation of underwater vehicles.