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This paper describes a prototype wireless underwater robot control system using a Time Division Duplex (TDD) Underwater Small Area Acoustic Network (USAAN) system with Orthogonal Frequency Division Multiplexing (OFDM) modulation. The prototype underwater robot can be controlled by the bidirectional link and can upload photo image data packets inside small underwater area. The TDD communication system consists of OFDM modem, Convolutional coder, Viterbi decoder and Cyclic Redundancy Codec. The underwater robot is controlled by Raspberry Pi small single board computer. The Base Station (BS) can send control commands to the robot by Type-length-value (TLV) data packets through the USAAN. Ocean field experiment has been performed at 500 m offshore from Yomitan coast, Okinawa prefecture Japan. Using a QPSK/16QAM modulation, basic robot movement control such as upward, downward, forward, backward, right-turn, and left-turn has been demonstrated. In addition, 240x213 pixels underwater photo could be captured and uploaded from the robot to BS. |
