Research On The Techniques Of Underwater High-speed Moving Target's Trace Measuring

In order to measure the three-dimensional trajectory of the underwater moving object accurately, the usual way is installing the recorder in it, so we can get the velocity, attitude, depth and acceleration of the object, the trajectory of object can be got using these above information. However, if the object is lost for some reason, these information can't be got, so it is significant to get the three-dimensional trajectory by exterior measuring system. SBL and LBL are the common exterior measuring system, but the two system are not convenient because it is difficult when launching and Recovery. Especially, LBL system has the lower refresh rate when working at transponder mode, so there is only little positioning point for high speed object. With the application of wideband signal and the development of signal processing, USBL system has higher positioning precision and more convenience, also there are many USBL products, but these products can't position and track high speed object. A trajectory measurement system based on USBL is designed for high speed object, this system works at synchronous mode, and can get high precision and refresh rate three-dimensional trajectory of underwater moving object, the system also has the ability of tracking multi-object. The main work of the thesis is as follows:The principle of USBL based on narrowband and wideband signal is proposed, also the positioning precision of two different methods is validated by simulation. Biphase coded signal is sensitive for doppler frequency, the signal detection will be affected seriously by doppler frequency because of object's high speed. We can suppose there is the same doppler frequency about signal on adjacent period, to overcome doppler effect a method of transmitting m-sequence signal alternately is proposed, a new correlateor is designed to counteract doppler frequency. A feature extraction method is proposed to resolve the near-far effects. A doppler estimate and compensation method are studied in the thesis, to the question of frequency ambiguity a ambiguity resolution method based on correlation peak time delay is proposed. Also, the range ambiguity being in system is studied, according as system characteristic, a simple and reliable range ambiguity resolution method is proposed.When the underwater object is lost and can't provide slant range, a position method based on bearing-only estimate is proposed. Though this method has lower precision than usual USBL, but the positioning problem is resolved when the slant range is absence.Traditional USBL is composed of three parts:acoustic positioning system, heading and attitude measurement system, GPS system. Misalignments between the different sensors lead to positioning errors, so the calibration is needed when using every time for USBL. Because of the inconvenience of calibration, a free calibration USBL system is designed, this system is only calibrated once, after that, the calibration of the system is not needed when using every time, so the system convenience is improved.Lastly, this thesis gives the detailed description about the composing of system, the positioning precision and performance is validated through a lot of experiments and dates.