The Research On Key Technologies Of “USV + Towed Array” Mobile Underwater Target Positioning System And Algorithm

Passive sonar is widely used in underwater target monitoring because of its good concealment and long range.However,in the face of my country’s vast territorial waters,complex maritime conditions,and island territorial disputes,the application of traditional passive sonar has certain limitations.Fixed-point positioning systems such as traditional shore-based fixed warning sonars and sonar buoys have limited detection range and no maneuverability,making it difficult to realize large-scale sea area monitoring and flexibly respond to complex situations;traditional mobile positioning systems such as side arrays and towed hydrophone arrays Operation and maintenance costs are high,and there is a risk of casualties when operating in dangerous sea areas.In order to overcome the above shortcomings,this article focuses on the "unmanned ship + towed array(hereinafter referred to as the unmanned ship towed array)" a new low-cost,flexible and maneuverable underwater target positioning method,focusing on the unmanned ship’s linear path tracking and low underwater acoustic signal Research on key technologies such as noise conditioning,high-synchronization precision sampling,and target location algorithms.The main tasks are as follows:1.Analyzed the functional requirements of the unmanned ship towing cable system based on the application scenarios,designed the overall scheme of the system,and analyzed the key technologies of using it to achieve underwater target positioning.2.In order to make the towing array system of the unmanned vehicle track the straight path to maintain the straight formation of the towed hydrophone array,a threedegree of freedom motion model and propeller thrust model of the dual-propulsion unmanned vehicle are established to analyze its motion and dynamic performance.Based on this,a linear path tracking algorithm combining line of sight guidance and PID(Proportion-Integral-Derivative)control is designed,and the PID control parameters are optimized through simulation,and the effectiveness of the algorithm is verified by the lake experiment.3.In view of the hydrophone output impedance is high,the signal is weak,the transmission path is long and vulnerable to interference and other problems,through the instrument pre-amplification technology,the effective matching of impedance is realized,and combined with the differential twin transmission method,the effective suppression of interference is realized;The circuit noise model was established,and the low noise design of the signal conditioning circuit was realized by means of gain preposition and low noise design.Aiming at the problem that the synchronization sampling error affects the positioning performance,based on the master-slave synchronous sampling model,a method combining the phase-locked loop and the master clock transmission delay correction was designed to realize the high synchronization sampling accuracy of each signal channel,and the synchronization sampling accuracy was better than 10 ns.4.In view of the limitation that the one-dimensional hydrophone array can only obtain the one-dimensional Direction of arrival(DOA)of the target,a two-dimensional DOA estimation method of the motion synthesis L-formation of the unmanned ship’s towing cable is proposed,and the data model of the motion linear array synthesis 2-dimensional L-formation is constructed.The direction cosine of the target is estimated independently by the time sharing of the single linear array,and the two-dimensional DOA of the target is calculated by combining the two direction cosines based on the two-dimensional data model.At the same time,the model of heading error and formation perturbation is established,and the influence mechanism and law of heading error and formation perturbation on the accuracy of two-dimensional DOA estimation are deeply analyzed.Simulation results show that the estimation method is effective and robust.5.The principle prototype of the underwater target positioning system for the unmanned ship’s towing cable is built,and the two-dimensional DOA estimation method designed is verified by experiments.