Research And Development Of Farmland Wireless Soil Pressure Sensor And Monitoring System

With the development of national agricultural mechanization,farmland soil mechanization over compaction has become an increasingly serious problem,causing serious impact on agricultural production.The internal performance of farmland soil compaction is the change of soil stress.In order to study the problem of farmland soil compaction from stress point of view,it is necessary to use the soil pressure sensor to understand the reason of soil compaction from the stress distribution of soil compaction.In order to solve the shortcomings of the structural size big of the soil pressure sensor prevalent in the market,disadvantages of soil pressure sensors for soil stress disturbance,And the lack of soil pressure sensor in the monitoring of soil stress distribution,at the same time in order to adapt to the soil depth of soil monitoring shallow,low internal stress characteristics,based on the development trend of modern agriculture,this paper has independently designed and developed a wireless barometric soil pressure sensor,and has developed a set of farmland soil stress monitoring system to achieve the expected function.The specific content and the conclusions of this paper are as follows:(1)Soil pressure theory calculation and matching error analysisIn this paper,under the condition of soil isotropic assumption and considering the interference of soil pressure sensor into soil in the soil in situ stress field,the soil pressure calculation and the matching error of soil pressure sensor and soil are studied theoretically to provide the theoretical basis for the design of soil pressure sensor with small and stable matching error.(2)Development of wireless barometric soil pressure sensorIn this paper,using pneumatic principle develops the soil pressure sensors.And using the rubber ball shell as a sealing element and the soil pressure of the original.And ultra low power consumption nRF24LE1 radio frequency chip,BMP180 pressure chip,rechargeable battery and wireless charging coil are sealed with rubber ball inside the shell.When the soil is subjected to the load,the rubber ball shell is deformed,and the pressure change inside the shell is sensed by the BMP180 pressure chip,which reflects the stress of the soil.(3)Soil parameters determination testIn this paper,the working medium of the soil pressure sensor is soil,therefore,in order to obtain soil parameters,in this paper,the experiment soil of Xiangyang Farm was used as experimental sample,and soil drying test,soil shear test,soil screening test,soil particle size determination test,etc is carried out.The soil bulk density,moisture content,cohesion,internal friction angle and soil gradation,equivalent particle size and other parameters were obtained.(4)Experimental study of wireless barometric soil pressure sensorIn this paper,the air pressure calibration test of the wireless barometric soil pressure sensor is carried out firstly.According to the data processing algorithm discussed in advance,the Matlab fitting toolbox is used to fit the test data,and the fitting function at loading is y1=464.30 · x1,the fitting function at unloading is y2 = 444.90·x2.The sand pressure test of the wireless barometric soil pressure sensor ia carried out,and the hysteresis loop is analyzed to explore the matching characteristics in the specific working environment.And obtain the elastic modulus of the wireless barometric soil pressure sensor and soil medium,to explore the applicability of wireless barometric sensors in measuring farmland soil pressure.From the test results analysis,the wireless barometric soil pressure sensor air pressure calibration test's linear error is very small,but the sand standard compared with the air pressure calibration test,there is a relatively large return error.The characteristics of the wireless barometric soil pressure sensor in the tests are consistent with the experimental characteristics of conventional soil pressure sensors.And through qualitative analysis and quantitative analysis of matching error,the matching error of the wireless barometric earth pressure sensor and the soil tends to be stable.From this point of view,this design of the wireless barometric pressure sensor can meet the requirements.(5)Design and realization of farmland soil stress dynamic monitoring systemIn this paper,based on the development of wireless barometric soil pressure sensor,combined with the development trend of modern agriculture,to complete the sensor acquisition side,transmission side,management platform design and implementation,Where the sensor acquisition side,the transmission side to complete the identification of soil stress gas' s pressure collection,determination of GPS location,send text messages and GPRS data transmission function.The management platform uses the Matlab GUI as the platform to realize the GPRS receiving,real time curve display and database storage function of the data,And according to the soil stress value and GPS data,can accurately determine the location of soil over compaction.The system provides a new method for analyzing and studying farmland compaction and guiding agricultural production.