Research On Real-time Monitoring Technology And System Of Air CO₂ Concentration Based On UAV

The increase of CO₂?carbon dioxide?concentration leads to global warming,which not only causes melting of glaciers,rising sea levels,and abnormal weather,but also results in a major reduction in production of major food products,posing enormous challenges to human survival.The increase of CO₂ concentration is accelerated currently;besides the human activities and the acceleration of industrialization,agricultural production is also an aspect that cannot be ignored for the acceleration of CO₂ concentration increase.It was found that,planting,tillage,irrigation,fertilization and other activities in agricultural production increased the CO₂emissions as well.China is a large agricultural country with the third largest area of cultivated land.In the past decade,Chinese researchers have begun to pay more attentions to the contribution of agricultural production to greenhouse gas emissions.Therefore,in order to monitor low-altitude CO₂ concentration in farmland,a rapid,flexible,reliable and suitable monitoring method for large farmland areas is required.It is quite important for the studies of CO₂ emissions caused by agricultural production and the reduction of agricultural CO₂ emissions.Based on UAV,sensor and CFD simulation technology,a real-time CO₂ concentration acquisition system based on UAV is designed in this study.The sampling accuracy of CO₂concentration is the main research object,and the airborne CO₂ monitor is determined in the unmanned Based on the installation parameters on the aircraft,the influence of the flight speed of the UAV on the measurement accuracy of the sensor is analyzed.The installation position of the airborne CO₂ monitor and the flight speed of the UAV are determined,and the CO₂concentration changes are generated according to the monitoring data of different monitoring points.The factors were initially analyzed.The main research contents and conclusions of the thesis are as follows:?1?The design of a CO₂ real-time monitoring system based on UAV.There are three parts of the system,UAV part,onboard CO₂monitoring part and ground handheld part.As onboard CO₂ monitoring part,an on-board CO₂ monitor including software is designed with G40 CO₂ sensor which is based on the non-dispersive infrared?NDIR?principle.The monitor can quickly detect the carbon dioxide concentration,store and display the data simultaneously.An independent real-time display ground handheld system is designed,the data transmission between ground handheld and onboard CO₂ monitoring part is performed by wireless communication.The UAV platform were assembled by considering the size and weight of the CO₂ monitor,and the UAV pre-flight calibration and PID tuning were performed.Finally,the UAV platform can be equipped with an on-board CO₂ monitor to smoothly complete the hover and flight missions.?2?Research on installation position parameters of UAV CO₂ monitors.As found through preliminary test,the wind speed has a great influence on the measurement accuracy of the sensor.Therefore,the fluid dynamics?CFD?numerical simulation method is used to simulate the airflow of the six-rotor UAV.Firstly,the 3D solid model of UAV and propeller is built by CATIA.The 3D solid model of the rotating and external flow fields of the propeller is created in ANSYS.The UAV watershed is solved and the airflow velocity and concentration around the UAV are obtained.The simulation analysis results show that the flow rate above the UAV increases first and then decreases.The maximum flow velocity occurs at 200 mm,and the maximum velocity is 2.3m/s.The area in front of the UAV shows a decreasing trend,and the maximum velocity is 1.6m/s.The area below the UAV increases first and then decreases.The maximum flow velocity occers at 200mm,and the maximum velocity is 2.2m/s.Within 100 mm around the drone,the area in front of the UAV is the most disturbed by the propeller,and the area below the UAV is the least disturbed.From the simulation results of concentration,it can be seen that within 400mm around the drone,the concentration under the UAV changes the most,and the concentration difference in the front area is the least.?3?Optimization of structural parameters of the UAV CO₂ monitoring system.In order to determine the best installation parameters of airborne monitors,the measurement errors of airborne monitors at different propeller speeds and distances were analyzed through indoor CO₂ concentration measurement tests.When above the drone,the measurement errors of the airborne monitor shows a trend of wave type increased,and with the increased of the propeller speed,the measurement errors of the airborne monitor gradually increased,and the minimum error is 0.40%at 20 mm.When under the drone,the measurement errors of the airborne monitor shows a trend of increasd first and then decreasd.With the increased of propeller speed,the measurement errors decreased gradually.The minimum error is 0.42%at 160mm.Because the flow velocity at 160mm below is far greater than that at 20mm above,the installation position of the airborne sensor was determined to be 20mm above the drone.?4?The determination of UAV flight parameters.The concentration and flow velocity distributions were analyzed by CFD numerical simulation and laboratory comparison method.The simulation results show that,with the increase of flight speed and propeller speed,the flow velocity near the monitoring point increases gradually as well.When the flight speed is1.5 m/s and the propeller speed is 3500 rpm,the minimum flow velocity is obtained.The test results show that,with the increase of flight and propeller speed,the CO₂ concentration near the monitoring point decreases gradually,and the sensor measurement error becomes larger.When the flying speed is less than 1.7 m/s,the measurement error is less than 3.8%.It is finally determined that,the optimal flight speed of the UAV for are 1.5 m/s and the propeller speed is 4500 rpm.Flight test of UAV monitoring system.The onboard CO₂ sensor are installed 20 mm above the UAV body,and the vertical monitoring test and flight test were performed on two selected points.The experimental results show that,the UAV flight is stable,the system measurement results are stable,the transmission display is normal.When the flight speed is 2m/s,the data fluctuation is small,and the error with the initial value is small,the UAV with CO₂ monitoring system can perform the measurement for flat flight and fixed-point hovering.?5?Field test application of UAV CO₂ monitoring system.Using the UAV CO₂ gas monitoring system to monitor the CO₂ concentration above three experimental areas of different water control treatment in Zhaojun Town,Dalate Banner,Inner Mongolia.The CO₂concentration data at the height of 5m,10m and 15m above the canopy in R growth period of maize were monitored.Combined with the ground water control treatment,the distribution of CO₂ concentration in the experimental areas was analyzed,and the vegetation growth was simply described.It can be seen from the analysis that the CO₂ concentration above the experimental area is the lowest at 18:00 p.m.and the highest at 8:00 a.m.And through the analysis of the change rule of CO₂concentration in a day,when the experimental area is6m×6m,it can be seen that the CO₂ concentration at 10m above the canopy is still affected by the growth of crops on the ground,while at 15m it is less affected by the ground.