An experimental investigation of the data delivery performance of a wireless sensing unit designed for structural health monitoring

Abstract

This study explores the reliability of a wireless sensing unit by testing it in a real-world university laboratory environment. The unit employs off-the-shelf products for their key components, while a flexible payload scheme was adopted for radio packet transmission to maximize throughput and minimize latency. The testing consists of two main parts: (1) a series of loopback tests using two off-the-shelf radio components with carrier frequencies of 900 MHz and 2:4 GHz; respectively, and (2) wireless transmission of a shake table response to a periodic swept sine excitation. The performance of the wireless channel is examined in each part of the study. Through this experimental investigation, it is validated that a loopback test may be used as a fast prototyping approach to characterize the complex transmitting environment of a structure in which a wireless monitoring system is installed. Various factors leading to signal attenuation are ranked according to their effects on packet delivery performance. Transmitting range and building materials are among the leading factors causing packet loss (and therefore data loss) in this specific testing environment. The severity of interference from 802.11b wireless systems in close proximity to the wireless sensing unit was investigated. Some preliminary results on the influence of operating rotating machinery and human activities are to wireless sensors were investigated. The results presented herein offer a guideline for applying wireless sensing within real-world structures so that the reliability of the wireless monitoring system is maximized. Due to uncertainties associated with the reliability of wireless communications, statistical analysis is performed on the collected time histories to reveal the underlying patterns associated with data loss. Temporal correlations of data loss were measured and found to be related to the adopted radio. A statistical distribution of the size of consecutive lost data points was further derived from the collected data. Such results have identified the need to further develop: (1) reliable communication

An Experimental Investigation of Applying Mica2 Motes in Pavement Condition Monitoring

“…Moist and rainy conditions were also beneficial in studying the performance of the selected wireless sensor network under undesirable conditions (for wireless communication). For essentially the same testing environment, a sperate study by some of the authors shows that the foliage condition does not play a significant role (Pei et al, 2008). Therefore, trees are not indicated in Figure 4.…”

“…Testing environment, especially the existence of building materials, the condition of traffic flow, and the weather during testing, are among the factors that affect the performance of wireless sensor networks (Shankar, 2002;Mark and Zhuang, 2003;Pei et al, 2008). As shown in Figure 4, the buildings are low-rise and sparse.…”

Energy-efficient deployment strategies in structural health monitoring using wireless sensor networks

“…In addition to energy-balanced routing, reliable routing is another major concern for wireless SHM systems [21][22][23]. However, communication reliability is outside the scope of this paper; reliable data transmission is assumed in this study and the authors analyze the reliability of the system related to SHM purposes only.…”

“…Minimizing (25) over d and m gives d * and m * such that moving away from (d * , m * ) will result in no improvement in the mode shape error or energy consumption that will not be outweighed by the decrease in the other measure. Figure 7 The weights in (23) and (25) are used to accommodate with different units and scales of the mode shape error and the energy consumption. The relative importance of the mode shape error and the energy consumption can be varied by adjusting the weights a M and a E , which in turn will affect the optimal solutions for d * and/or m * , favoring either the accuracy in mode shape estimation or the energy efficiency.…”

On-board data synchronization in wireless structural health monitoring systems based on phase locking

“…Nonetheless, the most important shortcomings of wireless SHM systems stem from the features that constitute their very benefits over cable‐based SHM systems . For example, however cost‐effective, eliminating wired connections adversely affects the reliability of data communication between wireless sensor nodes and servers . In this context, due to the absence of cables, wireless sensor nodes essentially operate as independent data acquisition units .…”