Application of Adaptive Disturbance Observer Control to an Underwater Manipulator

Hydrodynamics of the manipulator mounted on the vehicle are poorly known and time-varying. Furthermore, its motion is disturbed by the vehicle motion and current. This paper presents a non-regressor based adaptive control scheme with a disturbance observer for tracking the trajectory of underwater mobile platform-mounted manipulators. The presented control system does not require any information about the system. The disturbance observer regards the difference between the actual output and the output of the nominal model as an equivalent disturbance applied to the nominal model. The adaptive control law then estimates control gains defined by the combinations of the bounded constants of parameter matrices of the nominal model with disturbance error. The performance of the proposed control scheme was evaluated by a computer simulation with a two-link planar manipulator mounted on a one degree-of-freedom mobile platform. The effect of hydrodynamic forces acting on the manipulator was also considered.