Three-dimensional path-following control of underactuated unmanned underwater vehicle using feedback gain backstepping

To deal with the problem of path-following control for underactuated unmanned underwater vehicle(UUV) in three-dimensional space,we employ the virtual guidance and express path-following errors in the body-fixed frame.Firstly,the linear feedback control terms are designed to stabilize the position-tracking subsystem to avoid the complexity of computing the higher-order derivative of virtual control;then the dynamic controller is designed through backstepping method.Part of the nonlinear coupled terms can be eliminated by properly selecting the controller's parameters,which leads to the simplification of the virtual control and avoids the singularity problem encountered in traditional backstepping design.Robust feedback terms are designed based on Lyapunov stability theorem,and the uniform ultimate boundedness can be guaranteed for all states in the closed-loop path-following system.Simulation results demonstrate the high accuracy of tracking and good robustness against external disturbances achieved by the proposed controller.