Research And Design Of Temperature,Humidity,and Strain Sensor Based On RFID

In the field of civil engineering,in addition to structural damage caused by stress alone,which leads to house collapse and bridge cracking,other environmental parameters can also affect the life of large structures.Therefore,sensors used for structural health monitoring should focus not only on mechanical performance but also on monitoring the surrounding environment.The application of Radio Frequency Identification Technology(RFID)in Structural health monitoring makes passive infinite measurement possible and greatly reduces the application cost.In this paper,an integrated multi-parameter sensor based on RFID technology is designed to monitor strain and ambient parameters,and its performance is tested experimentally.The main work of this paper is as follows:1.This paper introduces the principle of RCS,the working principle of chipless RFID,and the design principle of microstrip resonators.The encoding label is designed by the combination of the microstrip model and the semi-ELC resonator,which proves the theoretical feasibility of ring splitting resonator as a strain sensor.The accuracy and feasibility of the model were verified by HFSS simulation and laboratory production.2.The working principle of chip-free RFID labels for temperature sensors is discussed.Through the analysis of substrates,it is found that the dielectric constant is mainly related to the size of the thermal coefficient and the dielectric constant itself.Based on an analysis of the obtained data,it is concluded that the resonant frequency varies linearly with the temperature.Explore the influence of humidity change on resonant frequency after covering PVA coating on the coding unit.It is concluded that the increase of the coating dielectric constant will lead to a decrease in the resonant frequency.The integration of temperature,humidity,strain,and encoding functions of the chipless RFID sensor is realized,and a matching broadband antenna is designed.The resonant frequency offset of the SRR resonant element in the strain part is linear to strain size.Humidity was in line with theoretical and experimental results.The feasibility and linear relationship between temperature change and frequency change are verified by experiments.3.Kalman filter algorithm is used for multi-sensor information fusion.First,STFT is used to obtain a time-frequency response,and then the sensor signal data is extended by the background noise data enhancement algorithm.Finally,the experimental results show that multi-sensor data fusion can improve the accuracy of information detection.4.A wireless detection system based on nano-VNA and Bluetooth modules is established,and an economical and flexible multi-parameter sensor wireless monitoring system is constructed by integrating a microcomputer controller,Bluetooth transceiver module,and nano-VNA with a PC master computer.The system is used for sensor measurement,which verifies the practicability of the designed system and compares it with the measurement results of large VNA.