Investigation of control strategies and development of a hydraulic actuator mechanism for accurate positioning of subsea robots

Subsea robot control must be robust in the face of dynamic uncertainties encountered in the unstructured ocean environment. In this thesis, the main control strategies are examined and evaluated in terms of their potential for underwater robot control. It is concluded that robust control would be achieved with a mix of supervisory and classical control strategies. In particular, neural networks and fuzzy logic combined with error-driven compensation are recommended for high performance underwater control. -- A new propulsion device for short duration fine-positioning control of small subsea robots is proposed. This device uses a hydraulic actuator mechanism operated from an energy source of compressed gas to mimic the jet propulsion of squids. Experimental work conducted demonstrated the potential of the proposed propulsion device