Abstract
Time-of-flight (ToF)-based 3-D target localization is a very challenging topic because of the pseudo-targets introduced by ToF measurement errors in traditional ToF-based methods. Although the influence of errors in ToF measurement can be reduced by the probability-based ToF method, the accuracy of localization is not very high. This paper proposes a new 3-D target localization method, Iterative Maximum Weighted Likelihood Estimation (IMWLE), that takes into account the spatial distribution of pseudo-targets. In our method, each pseudo-target is initially assigned an equal weight. At each iteration, Maximum Weighted Likelihood Estimation (MWLE) is adopted to fit a Gaussian distribution to all pseudo-target positions and assign new weight factors to them. The weight factors of the pseudo-targets, which are far from the target, are reduced to minimize their influence on localization. Therefore, IMWLE can reduce the influence of pseudo-targets that are far from the target and improve the accuracy of localization. The experiments were carried out in a water tank to test the performance of the IMWLE method. Results revealed that the estimated target area can be narrowed down to the target using IMWLE and a point estimate of target location can also be obtained, which shows that IMWLE has a higher degree of accuracy than the probability-based ToF method.
Highlights
Structural health monitoring (SHM) is an emerging technology that aims to design systems that are able to continuously monitor structures [1,2,3]
Time-of-flight (ToF)—the time taken by the ultrasonic pulse to travel from an actuator to a sensor—is a feature extracted from the scattered signals that are widely used in target localization [12,13]
We propose a 3-D localization method, Iterative Maximum Weighted Likelihood Estimation (IMWLE), which takes into account the spatial distribution of pseudo-targets
Summary
Structural health monitoring (SHM) is an emerging technology that aims to design systems that are able to continuously monitor structures [1,2,3]. Structural health monitoring is beneficial to the maintenance of critical structures in many fields [4], such as civil engineering [5] and aerospace [6], where damage detection plays a very important role. Damage detection of 2-D structures, such as plates and shells, has been widely studied [7,8,9]. Transducer elements act as actuators to emit short ultrasonic pulses, and sensors receive the scattered ultrasound. Time-of-flight (ToF)—the time taken by the ultrasonic pulse to travel from an actuator to a sensor—is a feature extracted from the scattered signals that are widely used in target localization [12,13]. Many studies have reported the successful application of ToF-based methods for target localization [1,4,14,15], but the accuracy is affected by ToF measurement errors
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