Composite Strain Detection System Based On RF Energy Harvesting

In the process of long-term service,the health states of the composite materials need to be detected in real time.In some special fields,there are application conditions that composite materials need long-term service and cannot be connected to power supply.Therefore,this paper studies the power supply mode of the composite strain detection system,and designs a composite strain detection system based on RF energy harvesting.The designed system includes two parts: RF energy storage module and carbon nano paper strain detection module.The RF energy storage module harvests the RF energy in the environment and converts it into a 3.3V DC power supply.It is composed of antenna,the double voltage rectifier circuit and the boost chip module are proposed.The HFSS software is used to optimize the antenna and a 70 mm × 70 mm double-layer circularly polarized microstrip patch antenna is designed.The measured results of the antenna show that the S(1,1)values at 1.8GHz and 2.45 GHz are-20.341 db and-25.53 db respectively.ADS software is used to simulate the voltage doubling rectifier circuit,and a voltage doubling rectifier circuit with the size of 50 mm × 30 mm is designed.The RF energy harvesting test is implemented for the antenna and voltage doubling rectifier circuit.The results show that the output voltage can reach 262 mv when the receiving antenna is 0.22 m away from the transmitting source.Carbon nanotube paper strain detection system detects the health of composite materials by carbon nanotube paper strain sensor which is surface bonded with the composite material.It converts the resistance change signal of the sensor into voltage signal through constant current source circuit.The voltage signal is converted into digital signals by the in-built AD in stm32l151 microprocessor,which collects the signals and transmits them to the host PC through wireless transmission module.Finally,the collected data is displayed on the host computer.The circuit of the detection system is made on a 70 mm × 60 mm PCB,and then the power consumption of the detection circuit is tested.The experimental result shows that the power consumption of the detection system is 1.8m J.According to the research of RF energy harvesting and power consumption of detection circuit,the system can implement strain signal collection once every 13 minutes.Finally,the strain test of the carbon nanotube paper sensor is implemented and the results are displayed on the host PC.The experimental results show that the resistance of carbon nanotube paper has a linear positive correlation with the strain of the stretching of the composite material.