| In order to implement variable fertilization,crop nutrition information is needed to obtain accurate firstly,while the traditional detection methods based on the laboratory is high cost,low efficiency and poor timeliness,so it is unable to meet the needs of variable rate fertilization in the field.As a new analysis technique,reflection spectrum detection technology has advantages of fast,nondestructive and convenient,which is getting more and more widely used in crop nondestructive testing.Using crop canopy spectral reflectance indices to detect crop nutrition and growth is a hotspot in the field of agricultural information at home and abroad now,combination of crop nutrition diagnosis model,which can realize rapid and real-time extraction of crop nutrition information,implementation to provide a reference basis of variable rate fertilization in the field.The application of canopy reflectance spectroscopy for the promotion of precision agriculture technology has an important practical significance.According to the active light source reflection spectrum measuring principle and measuring method by the team,the control circuit of spectral reflectance measuring instrument based on active light source,spectral reflectance measurement circuit and the software system were designed in this paper.The spectral reflectance measuring instrument can realize spectral reflectance measurement of two bands,which can provide the spectral reflectance and spectral indices measured values of two bands,using the measured values can be concluded that the spectrum nutrition diagnosis model.Finally,the reflection spectrum measuring instrument designed in this paper is used to carry out a series of static and dynamic performance tests in the field.The main research contents and results of this paper are as follows:(1)The demand of spectrometer in crop nutrition information nondestructive testing is analyzed,crop canopy reflected spectrometer research status at home and abroad is introduced,the advantages and disadvantages of the developed spectrometer at home and abroad were Enumerated and analyzed,finally the research target of this paper is determined.(2)The measuring principle,design scheme and function structure of spectrometer are introduced.According to the function structure determine,the design goal of detection and control circuit is determined.The detection and control circuit mainly includes the active light source control circuit and the reflection spectrum signal detection circuit.(3)The active light source control circuit is completed,which mainly includes the selection of active light source,spectrum stability study of active light source,the control circuit design of active light source and the structure of the active light source is introduced.(4)The reflection spectrum detection circuit design is completed,which mainly includes selection of photoelectric sensor,design of photoelectric sensor signal detection circuit and photoelectric sensor light path system is introduced(5)The development of hardware systems for the spectrometer is completed,which mainly includes the selection of circuit module chip,circuit simulation,circuit design and PCB drawing.The construction of the hardware system and the anti-jamming design of hardware circuit board are completed.(6)The design of the software system of the spectrometer is completed,which include the design of the PC interface and the design of the main program for single-chip microcomputer.(7)Performance tests of the instrument are completed.The experimental results show that the measurement result of crop canopy reflected spectrometer based on active light source designed in this paper is stable and reliable;NDVI value measured by the instrument has nothing to do with height.Under the condition of the static measurement,the volatility of the NDVI values measured by two instruments measured is within 5%.In the case of on-board measurement,the NDVI values measured by two instruments showed higher consistency.The spectrometer design in this paper has good dynamic performance,which can meet the needs of the vehicle-mounted mobile measurement in the field. |
