Development Of A Self-powered Sensor And Its IoT Platform For Applications In Bridge Vibration Monitoring

The safety of bridge is directly related to the safety of vehicles and pedestrians,traditional monitoring technology has no longer been able to meet the current diversified needs compatible to the modern information technology,and frequent replacement of sensor batteries is neither economical nor environmentally friendly.This dissertation research focuses on the wireless,remote and cluster monitoring technologies for bridges combined the status quo of bridge vibration monitoring and the deficiency of traditional monitoring,specifically the development of a low power wireless acceleration sensor,a wireless gateway and cloud platform following the Internet of Things(IoT)protocols,and the field evaluations of the newly developed system at different bridges.A new cantilever beam energy harvesting device has been developed in this paper,which can to power supply for sensor nodes.The main research activities and discoveries are described and presented as follows.A low-power,high-sensitivity wireless acceleration sensor was developed for bridge vibration monitoring.The sensor has an integrated circuit,data acquisition and wireless communication module,and sound packaging.The accuracy of the sensor in data acquisition is verified by calibration and performance comparison test.The sensor has the advantages of small size,easy installation and wireless data transmission,which overcomes the limitations of the traditional wired monitoring.A wireless vibration cantilever sensor was developed.A rectangular PCB structure was optimized by using theoretical calculations and numerical simulations.The natural frequency and data generation ability of the PCB were verified by experiments.Through integration of a signal conversion module,microcontroller module,a wireless transmission module and other supplemental components,a new type of wireless vibration cantilever sensor was developed.The sensor is applicable to the vibration monitoring of small bridges in an IoT sensor network.A new type of bridge vibration energy collecting device was developed.In order to improve the energy output of the PCB in the bridge-service environment,the influence of different shapes on the power generation capacity of the PCB was studied.The results show that the triangular PCB harvesters are more suitable for the low-frequency vibration environment of transportation infrastructure,and they usually have higher voltage outputs.In order to widen the resonant frequency of the triangular cantilever to better adapt to the random vibration environment of the transportation infrastructure,the performance of a hollow triangular piezoelectric cantilever beam(HTPCB)was also assessed.Through modeling and analysis,it is found that the resonant frequency of the HTPCB has a broader low frequency range.A rectangular piezoelectric cantilever beam with spring was studied,the experimental results show that the spring structure can broaden the range of resonance frequency and has a high output voltage.A hybrid piezoelectric energy collecting device which integrates triangular and rectangular with spring piezoelectric cantilever beam was designed,it can collect energy of multiple frequency bands of the bridge to power supply for sensors.A gateway which collects sensor data and transmits it remotely to the server wirelessly was designed and assembled.The gateway includes an integrated circuit,and a wireless data receiving and transmission module.The effective communication distance between the gateway and the sensor was estimated by communication performance tests.As the pivot of sensors and the cloud platform,the gateway communicates with the sensors with 470M frequency band.It was designed to have a capability to receive and process the data of the sensors within 600 meters,and then transmits the data to the server through 4G protocol.The gateway was designed to have a power management module,which is powered by lithium battery and solar energy for sustained power supply,A cloud platform was designed and developed which remotely receives and stores the data from the sensor via the gateway,and visually displays the data real time.The cloud platform has a Browser/Server and Model-View-Controller architecture,which includes a data layer,a logical layer,a presentation layer,and a client layer.As a terminal of IoT,the cloud platform can manage all targets being monitored in a unified manner.As part of the research for a national 863 project,the dissertation research has been highly recognized by experts of the evaluation panel for 863 project.In brief,this research has developed an IoT system for bridge vibration monitoring,which has been demonstrated practical and feasible.The IoT system for bridge vibration monitoring and the new piezoelectric cantilever beam sensor designed in this research form a set of self-powered IoT technology,which is highly promising for bridge health monitoring in remote areas.