基于FPGA的水下单程声径跟踪测速系统设计与实现

Design and Implementation of Integrated System for Underwater One-Way Acoustic Path Tracking and Velocity Measurement Based on FPGA

针对现有水下航行体的导航存在时延大和无法同时满足跟踪测速一体化问题,提出了一种基于单程声径的水下定位测速方法。相比传统长基线的双程声径定位测距,该方法基于高精度原子钟的同步系统,实现单程声径的目标测距测速。该水下定位测速一体化系统是基于具有快速并行计算能力的FPGA实现,解算结果可在微秒内完成,时延有效降低。针对目标跟踪测速一体化问题,水下航行体在系统同步时刻周期性发射线性调频信号,水下信标接收基阵设计基于短时傅里叶变换/逆变换算法对信号进行时频域转换分析,能够准确地提取信号的到达时刻和多普勒频偏。水下信标基阵进而可在系统同步周期内解算每个接收信标单元相对于水下航行体的径向速度和径向距离,实现目标的跟踪测速。仿真实验表明,该方法的跟踪相对误差控制在0.2%,测速相对误差控制在0.8 m/s。湖试试验结果表明,该方法跟踪相对误差控制在5%,测速相对误差控制在0.3 m/s。

Targeting at the problems that the navigation of existing underwater vehicles has large time delay and cannot meet the integration of tracking and velocity measurement at the same time,an underwater positioning and velocity measurement method based on oneway acoustic path is proposed.Compared with the traditional long-baseline two-way sound path positioning and ranging,the proposed method is based on the synchronization system of the high-precision atomic clock,and realizes the one-way sound path target ranging and speed measurement.The underwater positioning and speed measurement integrated system is based on fast parallel computing capable FPGA implementation,and the solution result can be completed in microseconds to reduce the delay effectively.Aiming at the integration of target tracking and speed measurement,the underwater vehicle periodically transmits a chirp signal at the time of system synchronization,and the underwater beacon receiving array is designed to transform the signals in the time-frequency domain based on the short-time Fourier transform/inverse transform algorithm.Analysis can accurately extract the time of arrival and Doppler frequency offset of the signal,and the underwater beacon array can then calculate the relative relationship between each receiving beacon unit relative to the underwater vehicle within the system synchronization period.The radial velocity and radial distance can realize the tracking velocity measurement of the target.Simulation experiments show that the relative tracking error of this method is controlled at 0.2%,and the relative error of velocity measurement is controlled at 0.8 m/s.The results of the lake test show that the relative tracking error of the proposed method is controlled at 5%,and the relative error of velocity measurement is controlled at 0.3 m/s.