Design Of Forest IoT Monitoring Node Based On Energy Harvesting Technolog

With the popularization of IoT nodes and wireless sensor networks,many researchers have applied them to the monitoring of forest ecological environment.Since IoT nodes are powered by batteries,batteries need to be replaced regularly,which increases labor costs and pollutes the environment.Based on the above status quo,energy harvesting technology has begun to attract the attention of researchers.However,the single energy harvesting efficiency in the forest is limited and cannot provide enough energy for the nodes.In this paper,by collecting wind energy and radio frequency energy in the forest environment to supply power to the node,the working time of the node is extended.The main research contents of this paper are:First,the structures of two types of wind energy harvesting devices,the inertial impact type and the pendulum vibration type,are proposed.Based on the positive piezoelectric effect and vibration theory,the theoretical model of the impact energy harvesting device was established,and the Fourier transform method was used to solve the model.The simulation and design of the structure were further carried out,and two prototypes of the wind energy harvesting device were processed.An experimental test platform was built,and vibration shock and wind blowing experiments were carried out.The results showed that the maximum power of the impact-type wind energy harvesting device was 22μW at a wind speed of 6m/s;much larger than the former.Second,a center-fed circular patch antenna is designed for RF energy harvesting.The antenna size is optimized by HFSS simulation,and the real object is produced.The measured bandwidth of the antenna is 4.8GHz-6GHz,and the highest gain is 5.69 d Bi.In addition,a single voltage rectifier circuit is designed through ADS simulation,and its maximum rectification efficiency can reach 50%.Finally,in order to solve the problem of the low collection density of the energy harvesting system and the threshold value of the chip,a hysteresis trigger circuit is designed,which can realize the intermittent charging of the battery.In addition,in order to relieve the working pressure of the energy harvesting device,a low-power IoT forest monitoring node based on theμ/COS-III operating system is designed.Pass the charging test of the energy harvesting device and the power consumption test of the node.It is realized that multiple energy harvesting systems can provide the node with the energy required for dozens of signal transmissions within200 minutes,which can effectively prolong the working time of the node.