| Soil is the most important resource for human production and life,but as industrialisation continues in China,the problem of excessive heavy metal elements in the land and heavy metal pollution in the soil is becoming more and more serious.High levels of heavy metals in soil are not only harmful to agriculture,but also to human health.Laser Induced Breakdown Spectroscopy(LIBS)has been widely applied in biomedical,military,space exploration,industrial process control and environment pollution monitoring.In response to the problems that the existing means of detecting heavy metal pollutants in arable soils cannot meet the needs of rapid detection of large areas,simultaneous co-measurement of multiple heavy metal elements,and long-term tracking and detection,based on LIBS technology and embedded technology,the following work has been carried out from the perspective of rapid real-time and stable detection and analysis by combining the unmanned carrier stage for unmanned carrier stage control and soil heavy metal element detection under laboratory conditions:(1)Building a LIBS detection system in the laboratory,optimising the detection conditions and acquiring spectrograms of soil containing heavy metals and analysing the data.Based on the above LIBS detection system,an unmanned carrier-based LIBS detection system was equipped to convert data acquisition under laboratory conditions to data acquisition by a test system under unmanned carrier conditions,prepare soil samples,and perform spectral acquisition and data analysis of heavy metal element Cr in the samples.(2)An unmanned bench based LIBS self-focusing detection control electronics system was designed.In this study,an embedded microcomputer was used as the main control platform,and a solid-state laser,a microfibre spectrometer and an embedded computer instrument were used as the core components to accomplish a number of functions such as high-energy laser generation,spectral acquisition,spectral processing and analysis.The GPS positioning module and the buck module are used as environmental or sample data collection modules,which are integrated with the self-developed circuit modules.The system hardware circuit diagram design and PCB board design were carried out using Altium Designer 20 software.On this basis,the LIBS self-focusing detection device was assembled and mechanically connected to the rail slider,the slider was driven using motor control,the UAV flight environment was simulated,the circuit performance was tested and verified,and finally the unmanned carrier-based LIBS self-focusing detection hardware system was built to realise the highly stable unmanned carrier data collection in the unmanned carrier simulated laboratory environment,and the electronics system was completed The on-line testing of this electronics system was completed.(3)The control software of the unmanned carrier-based LIBS self-focusing detection system was developed.Using the Linux operating system as the platform,the Qt development framework and the C++ language,a software with hardware device control functions and spectral data acquisition functions was developed.In order to realise these functions,the software development environment was set up on Ubuntu and Raspberry Pi respectively,and the compilation of the host-slave interaction was completed,and the software was finally successfully implemented.By programming the laser serial interface and calling the dynamic library of the spectrometer in Qt,the functions of laser control and data acquisition of the spectrometer can be completed.The software is easy to operate,has a simple interface,can effectively control the unmanned stage start/stop and speed,and can achieve the unmanned stage based spectral data acquisition.The system has good performance and can achieve rapid in-situ detection of heavy metal elements in soil.The stability and reliability of the system is verified by comparing the data collected by the ground-based unmanned bench test system with the test data from the laboratory bench.The stability and reliability of this soil heavy metal telemetry unmanned bench ground test system was verified through data acquisition and spectral comparison,providing a basis for future remote telemetry of heavy metals in arable soils with the LIBS system architecture on an unmanned aircraft. |
