Development of a biomimetic underwater microrobot for a father–son robot system

Underwater vehicles have been extensively applied to underwater intervention missions instead of human in recent years. As the crucial equipment of underwater vehicles, underwater manipulators typically play an important role in the underwater tasks. Generally, underwater manipulators are operated manually by human with remotely operated vehicles (ROVs). A KORDI ROV with a dual teleoperated manipulator was designed and developed (Jun et al. 2008). The ORION manipulator has six functional joints and one gripper. However, a ROV equipped with a rigid multi-link arm requires a depot ship for operations and the tether connected to the depot ship also restricts its positioning and manipulation performance. On the contrary, autonomous underwater vehicles (AUVs) do not require the depot ship and the tether. Thus, AUVs can achieve a better positioning performance and a higher flexibility than ROVs. Nowadays, only few AUVs are equipped with underwater manipulators. SAUVIM, capable of autonomous manipulation, performed an autonomous underwater intervention in the oceanic environment (Marani et al. 2009). And it completed an underwater recovery mission, which includes searching for the target and bringing it back to the surface. In addition, an underwater vehicle-manipulator system was used on an underwater robot with six degrees of freedom (DOF) (Mohan and Kim 2012, 2015). A 3-DOF underwater manipulator was mounted on the robot for underwater intervention. RAUVI, Abstract Conventional underwater intervention tasks are performed by underwater vehicles equipped with rigid multi-link arms. However, the movements of conventional mechanical arms exert reactive force on the vehicle platform due to their enormous bulk. Additionally, they cannot be used for small object recovery. In this paper, an ionic conducting polymer film (ICPF) actuator-based crayfish-inspired microrobot is designed and developed as a son robot for object recovery, which is connected to the amphibious father robot by copper wires. The crayfish-like son robot is used as the mechanical arm of the father–son robot system, which can grasp the small object especially in restricted spaces. The crayfish-inspired son robot actuated by ten ICPF actuators can realize underwater basic motions. The father robot can emit the son robot for object recovery. A proximity sensor is mounted in front of the microrobot between the two ICPF hands to implement the autonomous grasping motion. And we designed a blue LED-based underwater optical communication system to realize the communication between the father robot and the son robot for microrobot recovery. We carried out the