Modelling and workspace analysis for an underwater manipulator*

Manipulation tasks in underwater operations were so far only realizable with large work class remotely operated vehicles (ROV). However, new developments in the field of miniaturized fully-electric multi-joint manipulators are opening up applications for small and medium size ROVs. Despite miniaturization of the manipulators, the manipulator-to-vehicle ratio is not identical to that of large work class ROVs. Coupling effects between manipulator and vehicle must be taken into account to ensure good controller performance of the position and attitude of the vehicle and the tool center point (TCP) of the manipulator. In this paper, the modelling of an underwater manipulator based on an extended Newton-Euler method is presented. The proposed method is applied to a Reach Alpha 5 manipulator and validated by static measurements. Further-more, a method for collision detection between arm parts is presented and applied to the Reach Alpha 5 for workspace analysis.