A control module scheme for an underactuated underwater robotic vehicle

Despite major advances in Autonomous Underwater Vehicle design, the manually operated Underwater Vehicle (ROV) is still very much the industry workhorse. Current technologies are being used to reduce the stress of direct task operations by providing autonomy and to improve efficiency. This paper presents a design of a control module subsystem for a VE tele-operated ROV system. It discusses the design and implementation of the control module, Using modelling, simulation and experiments, the vehicle model and its parameters have been identified. These are used in the analysis and design of closed loop stabilising controllers for station keeping. As the vehicle has fewer actuators than possible degrees of freedom, it is necessary to limit the controllable degrees of freedom. These variables are eventually selected based on the inherent vehicle dynamics. Using the Lyapunov direct method, appropriate stabilising controllers have been designed. The station-keeping mode controller has PID structure and its gain values are designed using a non-linear optimising approach. Simulation and swimming pool tests for the heave and yaw directions have shown that the control module is able to provide reasonable depth and heading station keeping.