基于改进二维 MUSIC 算法的蓝牙信号到达角估计

蓝牙技术联盟在蓝牙 5. 1 规范引入寻向功能,为大幅提升蓝牙定位技术的精度提供了新的解决途径,但并未对信号的 角度测量算法提供统一方案。 针对低功耗蓝牙在室内环境多径干扰下到达角估计困难这一问题,提出了一种面向矩形阵列的 改进二维 MUSIC 算法,通过对矩形阵列天线阵元进行二次划分,采用前后向平滑的方法修正一维子阵的协方差矩阵,再利用接 收信号矩阵的广义逆求出各个子阵协方差的关系,从而修正整个阵列接收信号的协方差矩阵。 该算法在没有降低信号协方差 矩阵维数的同时,恢复了信号协方差矩阵的秩,有效抑制室内多径信源引起的干扰。 经过仿真实验,证明了本文算法在低快拍 数、低信噪比的情况下对角度估计的精度有着较大改善。 并设计了相应的硬件系统进行室内与室外的实验,结果表明在多径干 扰严重的室内定位时定位精度改善更为明显,室内定位圆概率误差降低了 26. 75% ~ 60. 25%。 仿真和现场定位实验证明了本 文提出角度估计算法的有效性,该算法对其他应用领域的来波方向估计也具有重要参考意义。     

Mass flow rate measurement of gas-liquid two-phase flow using acoustic-optical-Venturi mutisensors

The measurement of multiphase flow parameters is essential for the online monitoring of industrial production and energy metering. In this paper, a multi-sensor experimental measurement device is designed based on NIR, acoustic emission sensors, and throated Venturi. The measurement information is decomposed using modal decomposition, and the characteristic variables of the gas volume fraction are extracted by flow noise decoupling and light attenuation analysis. A new gas volume fraction model is proposed based on Gradient Boosting Decision Tree (GBDT) through feature-level fusion, and the Mean Absolute Percentage Error (MAPE) of the gas volume fraction prediction models is within 4% for the three flow patterns. A new flow rate model is established based on the Homogeneous and Collins models. Laboratory results indicate that the MAPE of the flow rate model is 1.56%, and 98.61% relative deviations are within ±20% error band. The study provides a new method for online measurement of multiphase fluid motion and a theoretical basis for sensing mechanism and measurement of multiphase flow.     

Velocity distribution of liquid phase at gas-liquid two-phase stratified flow based on particle image velocimetry

Horizontal gas-liquid flows are commonly encountered in the production section of the oil and gas industry. To further understand all parameters of the pipe cross-section, this paper use particle image velocimetry to study the circular pipe cross-section liquid velocity distribution rule. Firstly the focus is on the software and hardware combination of image correction system, to solve the influence of different refractive indexes of medium and pipeline curvature caused by image distortion. Secondly, the velocity distribution law of the corrected stratified flow (the range of liquid flow of 0.09-0.18 m³/h, and gas flow range of 0.3-0.7 m³/h) cross-section at different flow points of the pipeline cross-section at x=0 and in the Y direction at the maximum liquid velocity is studied. It is found that these distribution laws are caused by the influence of the interphase force of the gas-liquid interface and the resistance of the pipe wall. The current measurements also produce a valuable data set that can be used to further improve the stratified flow model for gas-liquid flow.