Structural Health Monitoring Using Smart Sensors - ideals ...

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.
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