Underwater Target Trajectory Measurement System Under The Line Geometry Situation

With the importance of maritime rights and interests in the world gradually highlighted,the degree of attention to naval equipment research and development is also increasing day by day in our country.As an important naval combat unit,submarine model self-floating test in the submarine dynamic performance test has been widely used.In this experiment,the movement trajectory of the submarine model is the key information to be obtained.For the convenience of the experiment,line structure is utilized to arrange the receivers,and the existing positioning method can not get the definite solution of the target position.Based on this practical application requirements,this paper designs an underwater target trajectory measurement system in a straight under the line geometry situation and studies the key technology of underwater acoustic positioning.Firstly,this paper designs an underwater moving target positioning scheme for the case of line structure receivers.The scheme combines the underwater acoustic ranging and underwater acoustic communication technology,and obtains the distance and depth value of the target at the same time.Thus the depth direction constraint is added to the positioning equation,and so that the equation has a unique solution.Next,focusing on the special conditions of the submarine model self-floating experiment compared to the general underwater positioning,including the high dynamics of the target motion state,the variability of the underwater acoustic channel,and the low positioning accuracy of the linear configuration,the key technologies of underwater positioning are studied,including :(1)For the Doppler effect caused by the highspeed motion of the target,In this paper,a two-step Doppler estimation method is designed by combining the Doppler estimation method based on ambiguity function and the Doppler estimation method based on frame interval.The frame interval estimation is used as the coarse estimation,and then the Doppler estimation based on ambiguity function is used to obtain the fine Doppler estimation quickly.(2)In view of the multipath effect in the variable underwater acoustic channel,this paper uses the equalization technology to suppress the inter-symbol interference in the communication caused by multipath,and designs a fractionally spaced fast RLS(Recursive Least Square)decision feedback equalizer.It integrates the advantages of the fractionally spaced structure,the decision feedback structure and the RLS algorithm.The RLS algorithm was modified to a form suitable for the fractionally spaced decision feedback structure,which greatly reduced its computational cost and made it more suitable for underwater acoustic communication.At the same time,based on the Multiple Hypothesis Tracking(MHT)algorithm,an fake trajectory elimination algorithm is designed.In the algorithm,the maximum amplitude assumption and the first arrival assumption are used simultaneously,and the Kalman filter is used to predict and track the target trajectory,so as to eliminate the false trajectories appearing in the target ranging values caused by multipath.(3)For the positioning method under the line geometry situation,this paper compares the positioning error of TOA(Time of Arrival)positioning method and TDOA(Time Difference of Arrival)positioning method under the condition of known depth situation,and concludes that TOA positioning method can achieve higher positioning accuracy.On this basis,The localization solution equation is modified to be suitable for the scheme used in this system.Then,the design of the underwater target trajectory measurement system is carried out,including:(1)The frame format design of the positioning signal.The signal format includes short frame and long frame signals,so that the system can adapt to different conditions of the channel.(2)The hardware and software design of the transmitter.The transmitter includes the transmitting and receiving circuit and the transceiver conversion circuit,so that the transmitter can realize the response mode.At the same time,the algorithm is optimized for the embedded system,so that the real-time performance of the transmitted signal is guaranteed.(3)The compilation of the host computer solver program at the receiving end.The output of the graphical user interface is designed and target motion trajectory can be painted.The maximum working distance of the system is 300 m,and the positioning results can be output 5 times per second.The accuracy of static positioning is better than 10 cm,and the positioning results of moving targets can be successfully obtained.The experimental results show the effectiveness of the designed system.At the same time,it is proved that it can meet the needs of self-floating experiment of submarine model.In summary,this paper designs an underwater moving target trajectory measurement system suitable under the line geometry situation,in which a positioning scheme combining underwater acoustic ranging and underwater acoustic communication technology is proposed,and the key technologies involved in underwater positioning in the submarine model self-floating experiment are studied.The experimental results show that the system designed in this paper can successfully obtain the positioning results of moving targets,and has high positioning accuracy.The research in this paper provides an effective solution for the trajectory measurement of underwater moving targets by using line structure receivers and has certain reference value for the research in related fields.