| Sowing operations are an important part of ensuring crop yield,and improving the quality and efficiency of sowing is of great significance for ensuring national food security.Pneumatic seeder has the advantages of strong adaptability,high efficiency,and saving operating costs.It has been widely used abroad and is the future development direction of domestic seeder.Due to the wide operation width and fast operation speed of the pneumatic seeder,once a row of the air flow distributor fails,it will affect the uniformity of other rows of seeding,and will cause serious leakage sowing and affect crop yield.In order to achieve rapid detection of leakage sowing,blockage and flow to ensure the quality of the operation,this paper designed a ladder array piezoelectric flow sensor,and carried out the test bench performance test.The main research contents are as follows:1.Piezoelectric impact detection technology and sensor unit design.The principle of piezoelectric detection is analyzed,and the frequency of the seed impact sensor is calculated according to the current seeding parameters to determine the design requirements of the sensor unit.through theoretical analysis,the key factors that affect the signal output of the sensing unit are obtained,including the material,size,structural form,etc.The normal force of the impact of the seeds of different directions and the sensitive elements of different materials is analyzed by EDEM software simulation,and the appropriate sensitive element materials are selected.The comparison test of multiple sensor units is designed,and optimized design is carried out by comparing parameters by comparing the parameters such as signal amplitude,frequency,and attenuation time.2.Sensor structure design.The arc and angular structure of the sensor is analyzed by CFD simulation of the Fluent software to determine the arc structure of the sensor.According to the analysis of the collision motion process,the parameters of the detection area are determined,and the sensor units are arranged along the outer circular arc array to improve the detection accuracy.The designed structure was modeled and optimized using CFD-DEM coupled simulation method.3.Design of signal conditioning circuit and acquisition system.According to the parameters such as the amplitude and frequency of the signal of the sensor unit,a signal conditioning circuit is designed to output the original signal as a pulse signal with a certain width.The parameters of electronic components were determined through theoretical calculation and Altium Designer software simulation.The signal acquisition system is designed based on the PIC microcontroller,and the information transmission is realized through the CAN bus.4.Bench performance test.Based on the existing seed meter performance test system,a pneumatic seed metering test system for air transport is built by adopting the fan,air flow distributor and metering device driven by servo motor,and the sensor was installed between the air flow distributor outlet and the seed tube.Calibration tests were carried out under different delivery pressures.The test results show that the delivery pressure has a greater detection accuracy for the flow rate and is approximately linear with the detection accuracy.Based on this,a sensor calibration measurement model is proposed.Performance tests were conducted under different metering quantity.The test results showed that the detection error was within 5%when the metering quantity was less than 170 seeds/s.And the sensor can realize the blockage alarm quickly and accurately. |
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