Design, fabrication and control of a 3-D printed SMA actuated underwater robotic manipulator

Abstract

The need for the usage of underwater robotic manipulators has increased proportionally with the attention to environmental challenges and resources, as well as general, scientific and military tasks and missions. ‘Underwater robotics’ is undoubtedly a rapidly growing study topic and a promising industry. R & D activities in the ROV & AUV communities have risen as advanced computing, new materials, sensory technology, and theoretical developments have been achieved. There are several underwater tasks that are challenging for direct manual execution. These tasks involve high risk due to the deep, unknown, hazardous territory, require high precision or are repetitive. This calls for a replacement of manual labor in the form of an underwater manipulator. This paper presents an innovative Shape Memory Alloy based Underwater Robotic Manipulator. Pre-existing study on underwater manipulators primarily uses primitive grippers with three to six degrees of freedom actuated via electric, motor-based or hydraulic means. The presented study showcases a novel design, incorporating a humanoid gripper, fabricated via 3-D printing with the material PLA (PolyLactic Acid) plastic - a highly biodegradable material, with seventeen degrees of freedom. The robotic hand is actuated by Shape Memory Alloy coil springs, the quietest actuation mode, thus ensuring that the aquatic life remains completely undisturbed. Special emphasis has been placed on the underwater feasibility and functionality of the design. As per this project, the adopted control mode for this manipulator is ON/OFF. Keywords: Robotics, Underwater Manipulator, Mechanical Design, 3-D Printing, Shape Memory Alloy, Control