<p class="MsoNormal" style="text-indent: .25in">The development and application of remotely operated and autonomous underwater vehicles have significantly increased in recent years due to technological advances in electronics, structures, and compact energy sources. As these vehicles operate in the water environment under elevated pressure and limited options for communication, demanding requirements to their design and manufacturing usually reflect in a high cost of underwater systems. However, with proliferation of relatively inexpensive electronics and powering systems suitable for small craft, as well as advanced manufacturing techniques, a number of low-cost developments in this area have been initiated. In the present work on a remotely operated vehicle, the starting point was a basic platform consisting of a plastic-tube frame, three thrusters, and a video camera, connected to control and powering modules above the water. Two propulsors provide thrust for horizontal-plane movement and steering, while the third, vertically-oriented propulsor is used for diving. The thrusters initially operated only in simple on-off modes. As functionality and navigation capabilities are very important characteristics for underwater vehicles, several modifications on this platform have been implemented. First, the propulsion control has been modified to allow for gradual variation of thrust forces. Second, a two-degree-of-freedom arm for manipulation of underwater objects has been constructed and integrated on the vehicle. One degree of freedom is a longitudinal extension of the arm outside of the vehicle frame, achieved with a hydraulic piston driven by a custom-built water pumping setup. The other degree of freedom is a gripper actuated by a waterproof servomotor. This arm arrangement allows for grabbing and moving underwater objects. The third enhancement included a computer vision system aimed at adding an autonomous capability for this vehicle, as well as for identifying and approaching underwater objects of interest, which can be subsequently manipulated with the arm. The computer vision system can be also used for self-localizing the vehicle in an environment with planted markers. Initial experiments of the vehicle with the constructed elements in a laboratory tank will be described and discussed. These tests include recognizing and approaching a target and grabbing and moving an object. The control signals and gathered information by the vehicle, as well as images recorded with an external underwater camera, will be analyzed and presented in the paper. The next development steps will aim at making this vehicle fully autonomous for open-water reservoirs using additional sensors, control actuators, and energy sources. For this purpose, a watertight chamber with computer boards and batteries is being designed. These future steps will be discussed as well.</p>

Implementation of 2-DOF Grabber Arm and Computer Vision on Remotely Operated Underwater Vehicle

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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