Experiments in automatic retrieval of underwater objects with an AUV

Automated retrieval of instrumentation packages from the sea floor is a task well-suited for autonomous underwater vehicles. By constraining the generic object-manipulation problem to one in which the object is specifically designed to be picked up by a particular robotic system, both sensing and manipulation can be simplified. Readily available vision processing hardware along with well-established vision algorithms can be used to locate the package. The strategy for automated object retrieval by an underwater vehicle is encoded using a finite-state machine (FSM). Each phase of the automatic pickup is represented by a state. As monitors detect the successful completion or failure of a phase, events are issued that trigger the FSM to transition to the next phase of the task or to an alternative, corrective action. These events cause the vehicle control system to change control modes or desired setpoints within the activated controller. The automatic retrieval task is demonstrated experimentally with the OTTER testbed.