A Multi-Step Source Localization Method With Narrowing Velocity Interval of Cyber-Physical Systems in Buildings

The localization for sources in the heterogeneous and complex media is of vital significance, which can be applied to monitor the invisible cracks and determine the potential damage areas of buildings with safety hazards. Based on the localization function with the model of arrival time difference (TD), a multi-step localization method (MLM) without premeasured velocity for heterogeneous and complex propagation media was proposed. The velocity interval used for localization was narrowed and optimized continuously through the multi-step localization, where the optimal velocity interval was determined when the velocity differences were less than the threshold. Then, the optimal localization results with higher accuracy corresponding to this velocity interval can be obtained with the TD algorithm. A source locating test was performed at a building of masonry structure. In addition, the locating accuracy was compared and discussed between the optimized MLM, the one-step method without premeasured velocity, and the traditional method with different premeasured velocity values. Results show that MLM is obviously superior to both the one-step method and the traditional method. The developed MLM can not only eliminate the errors caused by premeasured velocity, but also can improve the locating accuracy in the heterogeneous and complex media, which is an efficient and effective method for engineering applications.