Structural Health Monitoring Using Smart Sensors - ideals ...

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Table 7.6. Normalized Accumulated Stress Estimation Element ID Normalized Accumulated Stress Difference ( ) 3 0.6377 -2.1416 4 0.6662 0.3378 5 0.9751 4.9952 6 0.4506 -2.5601 7 0.3470 1.9430 8 0.6078 -5.3461 9 0.1368 0.2829 10 1.0000 0 11 0.6226 0.2349 configuration. However, cluster heads do not need to physically line up; rather they need to line up logically. In Figure 7.22, the manager sensor, CH1, notifies the cluster head to the right, CH2. The receiver cluster head also initializes itself and notifies the next cluster head. The initialization and notification are repeated until no cluster head to the right is found. The right-most cluster head then starts the procedure of finding inconsistent damage detection results. This cluster head first checks whether damage is detected in its sensor community. If not detected, the operation moves to the left cluster head. If detected, the cluster head inquires with the neighboring cluster heads whether the damage detection results are consistent. If inconsistent, a flag on the cluster heads involved in the transaction are marked as “RETAKE”. The search for inconsistency then moves to the left cluster head, where the procedure is repeated. This inconsistency search and transition to the left node are repeated until the process reaches the left-most cluster head. When the left-most cluster head finishes the inconsistency search, the process of reporting to the base station begins. The left-most cluster head reports damage detection results, i.e. damaged element ID and any inconsistencies, to the base station. After this cluster head finishes reporting, the operation moves to the right cluster head. This procedure is repeated until all of the cluster heads report their results. Then, the operation moves back to the manager sensor. While all of the nodes are designed to report DCS logic results to the base station for debugging purpose, the code can be easily changed so that only cluster heads with damaged elements report to the base station. The manager sensor then inquires of the other cluster heads whether local sensor communities organized by these cluster heads need to retake data. Only local sensor communities with inconsistent damage detection results participate in the next round of DCS. If the manager sensor in the previous round of DCS does not participate in the next round, one of the cluster heads takes over the manager sensor’s role. 125
1 2 Node ID 102 RETAKE 1 3 4 INCONSISTENT 5 6 Inconsistent Element ID: 8 7 8 ID 102 # of Damaged Element: 0 9 10 11 Node ID 91 RETAKE 1 12 13 INCONSISTENT 14 15 Inconsistent Element ID: 8 16 17 ID 91 # of Damaged Element: 1 18 19 Damaged Element ID: 8 Figure 7.23. Report on damage elements. This DCS logic is implemented on Imote2s and tested assuming acceleration measurement of the three-dimensional truss structure. Two Imote2s corresponding to cluster heads at nodes 4 and 6 receive simulated damaged element information from the PC. These two Imote2s then apply the DCS logic. Figure 7.23 shows the report from these two cluster heads after application of the DCS logic. In this case, the cluster head at node 4 is assumed not to have detected damage, while the cluster head at node 6 is supposed to have detected damage at element 8, as indicated in lines 8, 17, and 19. These two nodes find inconsistency and decide to retake data, as indicated by the RETAKE flag on lines 2 and 11. Node IDs on lines 2 and 11 are sensor node IDs unique to each Imote2 and different from the truss’s structural node IDs. The DCS logic implementation on the Imote2 is, thus, demonstrated. 7.2.6 Final implementation on the Imote2 With the developed components of DCS for SHM, the entire strategy is realized on Imote2s. Simple flow charts of the process are shown on Figures 7.24 and 7.25. DCS for SHM involves at least four sets of measurements: (a) measurement over the whole structure without mass perturbation for mass normalization constant estimation, (b) measurement over the whole structure with mass perturbation for mass normalization constant estimation, (c) measurement in a local sensor communities to obtain the base line flexibility matrix, F u , and (d) measurement in a local sensor communities for monitoring. All of these measurements require similar procedures, with the differences being: participating sensor members, the parameters injected at the beginning, and the numerical calculation applied to the ERA results. Extension of DCS for SHM using the SDLV, as explained in section 6.6, simplifies these steps. The SDLV does not require estimation of mass normalization constants, eliminating the need for the first two sets of measurement over the entire structure. The third and fourth sets of measurements are the same as the original DCS for SHM, with the exception being numerical operations in the DLV method. 126
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NSEL Report Series Report No. NSEL-
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The Newmark Structural Engineering
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Contents Page CHAPTER 1 INTRODUCTIO
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9.2.3 Power harvesting . . . . . .
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damage/deterioration is intrinsical
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scalability to a large number of sm
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logic circuit. However, FPGAs are m
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easons, smart sensors spatially dis
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Figure 2.1. EYES project sensor pro
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Table 2.1. Smart Sensor Specificati
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While a number of sensor boards for
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need to be within the coordinator's
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eing examined (Moore et al., 2001).
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structural damage, the analysis to
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that sensor installation cost inclu
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(2004) indicated that this accelero
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different type of sensors connected
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Chapter 3 SHM ARCHITECTURE This cha
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Modal operation Several modal opera
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its spatial gradient, which is clai
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Manager node Cluster head node Leaf
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commands; execution timing cannot b
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Table 3.2. Desirable Characteristic
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Table 3.2. Desirable Characteristic
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Figure 4.1. Foil strain gage. strai
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dB A s Figure 4.4. AA filter design
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8.32F 3V 3.45F 3V Input 1K 1K 1K 1K
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Strain ( ) 80 w/o Digital Filter 60
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performance was experimentally vali
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anges from 10 to 20. If 50 percent
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Node 1 x1 i =1,2,…,ns E x 1
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Correlation function estimate (m 2
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Figure 5.5. Effect of data loss and
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Frobenius norm. Because only a limi
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90 80 70 60 50 Node1 Node2 Node3 No
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On reception of a NACK, the sender
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Sender SendLData.send() Pack parame
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If there are missing packets, the r
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Sender SendLData.bcast() Pack param
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Sender Send a packet • Sender sen
Page 81 and 82: utilized in SHM applications follow
Page 83 and 84: where R xxref is a vector consistin
Page 85 and 86: Time (sec) 80 60 40 20 0 -20 -40 -6
Page 87 and 88: Difficulties encountered in realizi
Page 89 and 90: 1.8715 x10 5 #ofdatablocks 1.871 me
Page 91 and 92: Before this decimation is applied,
Page 93 and 94: where xn is the original signal,
Page 95 and 96: Timer firing every T3 110 data poin
Page 97 and 98: locks before or after the current b
Page 99 and 100: Chapter 6 ALGORITHMS In this chapte
Page 101 and 102: The eigenproblem of the system matr
Page 103 and 104: where M 0 is the mass matrix of the
Page 105 and 106: same community, eliminating the nee
Page 107 and 108: measurement or mass perturbation ca
Page 109 and 110: these algorithms are implemented on
Page 111 and 112: 10 0 10 -2 10 -4 0 500 1000 1500 20
Page 113 and 114: Table 7.1. SVD Accuracy Check on Ma
Page 115 and 116: 7.1.4 Complex matrix inverse A comp
Page 117 and 118: Figure 7.9. Details of the joint (G
Page 119 and 120: Figure 7.13. Amplifier (Gao, 2005).
Page 121 and 122: 0.08 0.2 Acceleration (g) 0.04 0 -0
Page 123 and 124: 3 Imote2_2/Imote2_1 Imote2_1/Siglab
Page 125 and 126: 200 3 Phase of spectral densities (
Page 127 and 128: 1.5 x10-17 Time (sec) Difference in
Page 129 and 130: input forces applied at nodes in th
Page 131: CH1 CH2 CH3 …. CHn-1 CHn Initiali
Page 135 and 136: Initialization: within local sensor
Page 137 and 138: PC Base station Manager sensor Clus
Page 143 and 144: Table 7.7. Instructions in DCS Code
Page 145 and 146: EXPERIMENTAL VERIFICATION Chapter 8
Page 147 and 148: 8 x10-3 Time (sec) Correlation func
Page 149 and 150: Table 8.2. Mass Normalization Const
Page 151 and 152: 1 2 Node ID 67 RETAKE 0 3 4 ID 67 #
Page 153 and 154: for a SHM strategy does not necessa
Page 155 and 156: are saved. The 420 seconds listed a
Page 157 and 158: 1 1 Normalized accumulated stress m
Page 163 and 164: Table 8.5. Summary of False Damage
Page 165 and 166: Table 8.7. Summary of False Damage
Page 167 and 168: e scalability, autonomous distribut
Page 169 and 170: The lowest frequencies of interest
Page 171 and 172: structural vibration is considered
Page 173 and 174: REFERENCES Actis, R. L. & Dimarogon
Page 175 and 176: Casciati, F., Faravelli, L, Borghet
Page 177 and 178: Feldman, M. & Braun, S. (1995). “
Page 179 and 180: Kling, R. (2003). “Intel Mote: an
Page 181 and 182: Mufti, A. A. (2003). “Integration
Page 183 and 184:
Sazonov, E., Janoyan, K., & Jha, R.
Page 185 and 186:
Yi, J.-H. & Yun, C.-B. (2004). “C
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