Development of an underwater humanoid robotic diver [electronic resource]
Keywords: Mechanical Engineering.

Oceanic discovery, be it the study of underwater ecology, archaeological exploration or sampling for marine science, requires skilled human access. However, a large part of the oceans is inaccessible to human divers; nearly nine-tenths of the ocean floor is at 1 km or deeper. While remotely operated vehicles (ROVs) are extensively used for deep sea exploration, they are largely designed for monitoring and inspection and thus do not come with manipulators. To incorporate manipulation capabilities, they are retrofitted with manipulators that are stiff and slow in response and thus are unable to perform compliant manipulation with maneuverability and dexterity that are comparable to human divers. These vehicles are also large in dimensions and thus are unable to access highly confined areas such as caves and cabins of shipwrecks. Moreover, the interfaces for these systems are non-intuitive and have limited operation modes. As a consequence, the extent that the human expert can interact with the environment via the ROV is restricted by the interface. This thesis presents the development of a novel bimanual torque-controlled humanoid robotic diver, Ocean One. Our design strategy is based on macro-mini coordination principles inherent in humans where manipulation tasks are performed by the arms (mini) while compensating for the slow dynamics of the body (macro). To design for these coordination capabilities, we conceived a whole-body design methodology that considers the functionalities of both the manipulator and the vehicle early in the design phase. This is in contrast to the design of commercial of the shelf systems where manipulators are retrofitted at a later time without considering vehicle-manipulator dynamics. Taking inspiration from the human diver, the manipulators of Ocean One were realized through a pair of redundant seven-degree-of-freedom serial manipulators. The actuators and link lengths were optimally sized to perform with characteristics similar to that of the human arm. To be able to compliantly interact with the environment, we selected torque-controlled actuators with series elasticity instead of hydraulic actuators commonly found. Taking inspiration from the human diver, the manipulators of Ocean One were realized through a pair of redundant seven-degree-of-freedom serial manipulators. The actuators and link lengths were optimally sized to perform with characteristics similar to that of the human arm. To be able to compliantly interact with the environment, we selected torquecontrolled actuators with series elasticity instead of hydraulic actuators commonly found in commercial position-controlled underwater manipulators. We adapted stock actuators from Meka Robotics to drive the manipulators. The design process of the vehicle was done while considering vehicle-manipulator coordination requirements. We analyzed the relationship between the vehicle's shape and its inertial properties. Based on the results, we placed the watertight electronic compartments, oil compensators, foams, and battery assemblies so as to achieve optimal vehicle shape. Analyzing manipulator placement in the context of macro-mini coordination, the manipulators were mounted such that the available vehicle-manipulator coordination workspace was enlarged. To determine the optimal thruster configurations and sizes, we analyzed these parameters in the context of docking maneuvers. The thruster configuration and sizes were selected such that sufficient vehicle docking decelerations could be produced to prevent saturation in the manipulators' range of motion. The optimized system demonstrated desirable coordination behaviors and enhanced impact mitigation capabilities due to its macro-mini structure. In collaboration with the French Ministry of Culture and Communication (DRASSM), we deployed Ocean One on its maiden dive in the Mediterranean Sea in the spring of 2016. Ocean One successfully recovered a 17th century vase at the depth of 91 meters from the shipwreck site of the Lune. This experience from the field tests brought about new design ideas, which will be incorporated in future generations of Ocean One.