Trajectory Tracking Control of Underwater Vehicle-Manipulator System Using Discrete Time Delay Estimation

A new nonlinear robust control scheme is proposed and investigated for the trajectory tracking control problem of an underwater vehicle-manipulator system (UVMS) using the discrete time delay estimation (DTDE) technique. The proposed control scheme mainly has two parts: the DTDE part and the desired dynamics part. The former one is applied to properly estimate and compensate the complex unknown lumped dynamics of the system, using the intentionally time-delayed system's information. The latter one is used to obtain the desired dynamic characteristic of the closed-loop control system. Thanks to the DTDE technique, the proposed control scheme no longer requires the detailed system dynamic information or the acceleration signals, bringing in good feasibility for actual applications and satisfactory control performance. The stability of the closed-loop control system is analyzed and proved using the bounded input bounded out stability theory. Finally, nine degree of freedoms (DOFs) simulation and seven DOFs pool experiment studies were conducted to demonstrate the effectiveness of the proposed control scheme with an UVMS developed in our laboratory. Corresponding results show that our proposed control scheme can ensure satisfactory control performance with relative small control gains and obtain a precision of 0.064 m for the end effector in the task space.