This paper presents a study of the dynamics of undersea robot manipulators in an unstructured sea water environment and a control scheme appropriate for manipulating them. Under the sea, the buoyancy and the added mass should be considered in modeling the dynamics of the robot manipulators. However, due to the complexity of the modeling of the added mass, the dynamics of the robot manipulators are treated as an unmodeled dynamics in this paper. In addition to the buoyancy and added mass/moment of inertia, disturbing forces due to drag, and current affecting the dynamics of the robot manipulators should be considered. In this paper, the forces due to the drag are defined as disturbance forces in addition to the frictional force of manipulator joints. In order to control the manipulator, a robust control scheme is devised to achieve trajectory tracking while regulating disturbance forces. A numerical example is shown.

In this paper, we propose a robust controller for the tracking of robot motion. This controller is a nonlinear-based controller that compensates for the uncertainties present in the manipulator dynamic equation. The main result of this paper is that we explicitly show how the response of the tracking error can be modified by adjusting the control parameters. The corresponding stability result for the tracking error is Global Exponential Stability (GES). We then illustrate how similar control approaches are related to the proposed controller. Finally, simulation and experimental results are utilized to illustrate the performance of the robust controller.