Synchronized Sensing and Network Scalability of Low-Cost Wireless Sensor Networks for Monitoring Civil Infrastructures

Synchronized Sensing and Network Scalability of Low-Cost Wireless Sensor Networks for Monitoring Civil Infrastructures.

Introduction to Structural health monitoring and Wireless sensor networks. Objectives. Introduction to the developed low cost Wireless sensor node. Introduction to synchronization. Synchronized sensing method. Application, verification and reliability of the method. Cost aspects of the developed wireless system Conclusion. References..

Structural Health Monitoring. The process of implementing a damage detection / health threat and characterization strategy for engineering structures / human is referred to as Structural Health Monitoring (SHM)..

Structural Health Monitoring. Cra A. Bridges. Aircraft.

Importance of SHM. To understand better how civil infrastructures really perform which differs from the calculated or designed behaviour due to, Over-estimated or under-estimated loads. Inability of codifying the exact wind and seismic load for unusual site and geometric conditions. Inability of predicting site conditions such as soil-structure interaction and impact due to close by structures. A structure has should be used as a living laboratory and the realistic behaviors should be captured and used for future designs..

Metric Wired Sensor Networks Wireless Sensor networks(WSN) Number of Sensors Less because of the difficulty in installing Higher due to ease of installation Cost Very high $10,000 to $25000 Low it would only cost around $600 per node Deployment Time Very long and it would take several days Short it would cost only few hours Life span Long, Typically limited by hardware life span Short, Typically limited by node battery life time Connection bandwidth Higher band width due to wired connection Limited band width and unreliable connection Data rate High sensor data rates Lower sensor data rates but higher than conventional Sensor Synchronization Very high due to wired connection Concern due to wireless connections.

Objectives. To develop a low-cost wireless sensor node capable of collecting precise data with high frequency with low cost involved. To incorporating Synchronized sensing technology and synchronize the nodes with acceptable jitter. Establish the developed Wireless sensor network on a target building and verify the performance of WSN using MAC..

Developed Sensor Node. A close up of a device Description automatically generated.

Functioning of Sensor Node. The master node at the proximal center of the network will synchronize all the other nodes with respect to its clock, which is done by CC1310 Launchpad which uses Sub 1 GigaHertz (800m range in open air) After all the nodes have been synchronized, CC1310 sends a signal to the Raspberry Pi through its General Purpose Input Output pins (GPIO), which will trigger the Raspberry Pi to start collecting data Using Inter-Integrated Circuit (I2C) protocol, MMA8451 collects the data and sends it to Raspberry Pi which will be stored in a 32GB microSD card. After 40 minutes worth of data is collected, the node will start this process again..

Synchronization. A clock on each of it s sides Description automatically generated.

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Synchronization. Synchronization error (Jitter) needs to be less than 120 μs for precise phase angle calculations. The primary reason for synchronization is that each collected data by a particular node has to be matched with the data collected at the same time by another node of interest. If the jitter exceeds beyond 120 μs, the calculation of phase angle calculations will be erroneous thus affecting the following. damage detection Localization error.

Peak Matching Method. A close up of a piece of paper Description automatically generated.

State of the art synchronization protocols that is available at present for WSNs which has achieved jitter at the range of 0.5 µs. Due to having hardware specific requirements in mote devices such as having an SFD pin and separate radio and CPU cores for the implementation, the cost of a single node increases, which increases the cost of the whole network drastically..

Synchronization implemented in the current system.

The chronological order of events of the synchronization in the developed system.

Node. Master. Timestamp 1. Timestamp 2. Process. Timestamp 3.

Identification of Jitter at the Laboratory Level.

Scaling of the WSN. Hop Hop Hop. Hop Hop Star Topology.

Laboratory level test showed that synchronization jitter is NOT increasing linearly when the WSN was expanded to multi hop system. This is an encouraging results which leads to scaling of developed WSN to a multi hop system without compromising the synchronisation. Further experiments are under progress at insitu level to check the pragmatic way of establishment..

Application on Target Building. øøø øøø gur.

FEM of Target Building.

Mode 1: T = 5.893s f = 0.17Hz. Mode 4: T = 1.935s f = 0.517Hz.

Mode 5: T=1.797s f=0.557 Hz. Mode Natural frequency (Hz) Mode shape 1 0.17 Translational 2 0.178 Translational 3 0.335 Torsional 4 0.517 Torsional 5 0.557 Torsional.

Establishment of WSN at various phases in the target building.

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Phase 6. 3. Level 36. Level 38. 1. li- i? i? iiiili:i iä.

Phase 11. Level 24. 1. Level 23. 3. li l: II: II:II: j:.

Mode shapes –Using Response time history. 3 3 3 s 5 s 7 7 9 9 9 9 17 19 21 23 2s 27 29 31 3s 37 39 a: 43 as 47 49 19 23 25 29 37 39 41 43 45 47 49 11 17 19 21 23 2S 27 29 33 39 41 as as 49 15 17 21 23 25 27 33 3 17 19 21 23 27 29 31 33 •s 3 41 43 as 47.

Modal Assurance Criteria(MAC). Modal assurance criteria (MAC) takes value from 0 to 1, where 0 represents no consistent correspondence and 1 represents a good correspondence. Values larger than 0.9 indicates a satisfactory level of correspondence. All five modes considered were compared using this method and it could be observed that the modal assurance values were closed to 0.9..

Cost of the Node. Component of the node Cost of a unit (in USD) Quantity Total cost (in USD) Raspberry pi 3B+ 35.00 1 35.00 CC1310 Launchpad 29.00 1 29.00 MMA8451 Accelerometer 7.95 1 7.95 81-MXFR01JA1000 cable 21.83 1 21.83 712-ANT-868-CWHWRRPS 11.17 1 11.17 32GB microSD card 9.34 1 9.34.

Cost Comparison. Project Cost of a Sensor node (in USD) Node of this system 114.29 Straser and Kiremidjian et al. (1998) [16] 598.50 Bennett et al. (1999) [17] 590.61 Lynch et al. (2001, 2002b) [18] [19] [20] 389.06.

Conclusion. A Low cost WSN was successfully established in target building with jitter within allowable limit. Using Synchronised sensing method the maximum jitter was kept below 90 µs. The mode shapes calculated using time history response captured using developed low cost WSN resulted in MAC values close to 1. The cost of the developed node yielded 70 % of cost saving compared to the sensor nodes currently used..

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Thank You. Questions are welcome..