Many underwater tasks such as ship-bottom cleaning, collection of samples, maintenance of underwater construction are required as diver-works. However, allowable depth and time of diver activity are very limited. Therefore, use of underwater robot arms is expected in place of divers. In general, underwater handling tasks are needed in diver-works. For handling by robot arms, measurement of force/torque is very important. This paper proposes a new joint-torque measurement method for underwater robot arms. The proposed method ensures waterproof and joint-flexibility by using the series elastic actuator mechanism and hall sensors. Performance of the proposed method is confirmed by some experimental results.
