Three-dimensional straight line path-tracking control for underactuated underwater vehicle

To deal with the three-dimensional straight line path-tracking control problem for underactuated underwater vehicle(UUV),we develop the three-dimensional path-tracking error equations based on the virtual guidance law.The feedback gain backstepping technique is adopted for designing the path-tracking controller,so that a part of the nonlinear coupled terms can be eliminated by properly selecting the controller parameters.This leads to the simplification of the virtual control variables compared with the traditional backstepping design,and the avoidance of the singularity problem encountered in designing the line-of-sight(LOS) guidance law.Asymptotic stability of the closed-loop tracking-error system can be proved by using Lyapunov stability theory.Simulation experiment is carried out for the controller applied to the UUV;the results validate the accurate tracking ability and good robustness of the proposed control scheme against current disturbances and model parametric uncertainties.