Research On Detection Of Yield And Seeding Rate Of Cotton Based On Capacitive Method

With the development of mechanical planting and harvesting for cotton, the demand for precise and intelligent detection system for seed cotton yield and seeding rate are rising. The accurate cotton yield information can examine the implementation effect of precision agriculture in the current year and provide the important reference information for variable rate prescription map in the coming year. The monitoring of seeding rate is the key to successfully implement the variable seeding, but also the basis to determine seeding performance. Therefore, studying on the online detection method for seeding rate and cotton yield has very important significance to reduce cotton production inputs, increase cotton production and reduce environmental pollution.In this research, a new method based on capacitive sensing for detecting seed cotton yield and seeding rate was proposed. Some thorough research work on the method were done to assess it.Then, the project application was realized.The dielectric property of seed cotton was studied firstly. Meanwhile, according to the pneumatic conveying characteristics of seed cotton, the detection method for seed cotton conveying velocity based on dual capacitor cross correlation technique and method for seed cotton mass flow based on single capacitive sensor were proposed.The correlation method was to use the time correlation between the two capacitive sensor signals,combined with the sensor spacing,for detecting seed cotton conveying velocity.The other method was to use capacitive sensor signal to detect the mass flow based on the conveying velocity under conditions of stable in the harvest process.The differential shaped capacitive senson was densined. The finite element method was used to analyze the sensor by using ANSYS and the experiments were conduct to verify the simulation results.Based on the design of capacitive detection circuit and microcontroller information acquisition and processing system, the conveying velocity and mass flow of seed cotton was obtained.The cotton yield monitor system base on CAN bus was developed in CASE CPX620cotton harvester, which includes interactive computer terminal, seed cotton mass flow sensors, microwave moisture sensor, GPS receive.Through research of key technologies and system integration,the cotton yield based on latitude and longitude information,as well as cotton harvester working condition parameters were acquired online. With the help of the Labwindows/CVI software development platform, upper computer data acquisition and processing was completed and the foundation for the multi-information fusion was laid.To assess the cotton yield monitor system, the free-falling experimental device was build.According to the results of the temperature and variety change test,the sensor have a better adaptability to temperature and variety. One kind of seed cotton named "xinluzao43"is used as sample to study the influence of cotton moisture content on the output capacitance value of mass flow sensors, and the relationship of cotton mass flow and sensor output capacitance. The relationship among cotton moisture content, mass flow rate and capacitance value can be described by a bivariate regression model. The laboratory experiment results show that, the predictive error of static model is4.7%and error of dynamic model is9.07%. The field experiment results indict that the determination coefficients of the model for cotton mass and capacitance variation is0.94.In addition, the spiral shaped seed sensor was designed in the paper.The sensor could capture the dynamic information when seed went through it, then the seeding rate for drill was detected. Meanwhile, the dynamic information was converted into digital pulse signal in order to get the information of seeding rate and missing rate and multiples rate.The seed pulse was smoothed by Savitzky-Golay smoothing method to get the optimum signal noise ratio. Combined with the first derivative and threshold condition, the cotton seed pulse was identified rapidly.The pulse position and boundry information were also obtained.According to the pulse integral area, the double seed could be detected, which could help to improve the seeding rate monitor accuracy.At the same time, the monitoring system based on CAN bus was constructed to realize high reliability monitoring of sowing quality levels. The laboratory experiment results showed that the system can realiz the missing and blocking alarm, and the system accuracy for single seed detection is up to97.3%, and the system has an accuracy of94.6%in seeding quantity,93.5%in missing detection and88.1%in multiples rate.