Application Of USBL Positioning Technology On Underwater Submersible Interfacing

The 21st century is a new century for mankind to exploit and utilize the ocean resources comprehensively. Deep sea space station is a possible platform for ocean sea resources exploitation. Shuttle submersible is an important component of deep sea space station, which can transport the materials and staves between deep sea space station and surface vessels. The dissertation focuses on the positioning technologies of USBL (ultra-short base line) in shuttle submersible, including high-precision positioning method of USBL, multi-target positioning method, installation error calibration method, positioning and attitude measurement method, etc.The precision of USBL depends largely on the direction finding of array, which can be obtained by phase difference estimation or time delay estimation. According to Crammer-Rao Bound Limit (CRBL), the estimation precision is restricted by SNR (signal to noise ratio) and signal bandwidth. In order to improve this precision, we propose the following methods. A new array shape is designed for this system, which breaks the traditional array design. In the condition of large aperture array, anti-ambiguity of phase measurement becomes challenging. The design of dual-pulse waveform is proposed in the case of narrow band signal. Meanwhile, in the situation of wide band signal, a new phase unwrap method is suggested, which can be implemented easily in the engineering. Both theoretical and simulation results are given to verify the correctness of these methods. Consequently, what the author presented here simplifies the array engineering design and reduces the system complexity at certain positioning precision.Acoustic sensor, attitude sensor and GPS, etc, constitute the USBL system. Different locations of these equipments cause the installation errors, which can be eliminated by coordinate transformation. This method is called installation error calibration. Conventional calibration method based on the average sound speed can not satisfy high-precision positioning requirement due to the error introduced by the bending of sound ray in deep sea. Installation error calibration method based on ray tracing is presented here, which has been proved effectively through simulation and sea trial.To implement underwater mechanical interfacing, we need to know the relative position and attitude information between the shuttle submersible and deep sea space station. Multi-target positioning method using hopping-frequency signal based on COSTAS array and the signal based on the OFDM combined with GOLD sequence is also studied in this dissertation. The author proposes a position and attitude solution algorithm and suggests an interfacing criterion. Finally, sea trial data proves it effective.