Study On Design And Key Technology For Sunflower Combine Harvester Online Yield Monitor System Based On Pneumatic Conveying Structure

The online yield monitoring system of combine harvester is the main starting point for the implementation of precision agriculture and the primary task to improve the production management system of precision agriculture and promote smart agriculture.Sunflower planting area in China exceeds 13.72 million acres,mainly planted in Inner Mongolia Autonomous Region,with a planting area of 8.82 million acres.The traditional sunflower yield measuring method is to estimate the yield by manual sampling or direct bagging and weighing.Such methods are used in large-area farmland,which are labor-intensive and inefficient,and can only get the average yield of the plot,which does not meet the implementation prerequisites of precision agriculture.At the same time,sunflower harvesting operation has the current situation of seasonal labor shortage,average age of farmers,high cost of inserting trays and beating seeds.How to obtain sunflower spatial distribution yield online has become an urgent problem for the implementation of precision agriculture development in sunflower industry in China,and the development of sunflower combine harvester online yield monitoring system is an objective requirement and inevitable trend for the sustainable development of precision agriculture in sunflower industry.Considering that the current yield measurement methods mainly focus on the research of the net grain conveying structure as scraper-type lifters and grain yield monitoring.To this end,this thesis conducts research on sunflower combine harvester yield measurement methods and system development,and constructs a sunflower combine harvester online yield monitoring system applicable to pneumatic grain conveying structure based on the analysis of sunflower seed conveying motion characteristics of gas-solid coupling,aiming to improve the application of the yield measurement system to different combine harvester structures and different harvested crops,in order to accelerate the development of intelligent agricultural production management system in China.The main research contents and research results are as follows:(1)Sunflower seed discrete element simulation model establishment.Three sunflower seed varieties,1013,SH361 and SH363,which are mainly planted in Inner Mongolia Autonomous Region,were selected to establish the three-axis size function relationship of sunflower seeds,and the optimal combination of parameters for discrete element simulation of sunflower seeds was obtained by using the sunflower seed calibration model.Meanwhile,according to the sunflower seed particle triaxial size function relationship and sunflower seed particle geometry,the sunflower seed discrete element model establishment method was proposed,and the multi-spherical sunflower seed particle discrete element simulation models with different roughness(25 sphere,28 sphere,31 sphere,34 sphere,37 sphere,40 sphere)and different shapes of polyhedral sunflower seed particle discrete element simulation models(rectangle,trigonal cone)were established,by comparing the rest angle,volume density simulation test results and CPU simulation computation time,it was found that when the number of constituent spheres was greater than or equal to 31 spheres and the rectangular polyhedral model was selected,the simulation test results were within the standard deviation of the physical test,and the CPU simulation computation time of the polyhedral model was significantly less than that of the multispherical model.(2)Analysis of sunflower seed pneumatic conveying mechanical characteristics.Based on the analysis of the working principle of 4ZXRKS-4 type self-propelled sunflower combine harvester,the Reynolds number of airflow in the pneumatic grain conveying pipeline of the harvester was calculated,and the flow state of air in the pneumatic conveying pipeline of the harvester was determined as turbulent flow.Combining with theoretical analysis,gas-solid two-phase flow coupling simulation and laboratory high-speed photographic bench test,the research of airflow field flow law and sunflower seed motion characteristics of pneumatic conveying device was carried out.The mathematical models of the average flow velocity of airflow in the pneumatic conveying pipeline and the fan speed were established respectively,and the kinetic models of sunflower seeds under the action of airflow from the acceleration zone,inclined pipeline,bend pipe and after leaving the discharge port.At the same time,the mathematical model of fan rotational speed and sunflower seed velocity was built,and the airflow velocity at the outlet of the conveying pipe under different inlet wind speeds and the seed velocity under different wind speeds at the same outlet position were analyzed.(3)Research on the design of online yield monitoring system for sunflower combine harvester.By using Solid Works Simulation mechanical simulation design software tool,we focus on the design of sunflower seed flow sensor,determine the impact plate of sunflower seed flow sensor and elastic element with intermediate solid support method through static analysis and frequency analysis,and establish the kinematic characteristics of sunflower seeds and its mechanical principle of the action on sunflower seed flow sensor by analyzing the voltage and The binary yield model of sunflower kernels with the parameters of fan speed was established.Based on the microcontroller controller and programmable touch screen,the online yield measurement system of sunflower combine harvester is designed with modular double-layer circuit board,and the IOT cloud box monitoring platform is developed by applying the IOT cloud box as the data transmission module.Based on RS485 bus technology,the system realizes the functions of real-time data collection and centralized display of sunflower seed flow sensor,fan speed sensor and agricultural machine positioning module,real-time yield data change curve drawing,and operation data packet export and forwarding.(4)Yield measurement signal processing and field test.Adaptive CEEMD wavelet threshold denoising algorithm is used to reduce the noise of the sunflower seed flow sensor signal.According to the characteristics of the sensor voltage signal itself,the signal is decomposed into IMF components from high frequency to low frequency,and the high frequency IMF components with low signal-to-noise ratio are denoised to obtain the voltage signal that can be used to build the yield model.The average yield measurement error in the field after processing by the adaptive CEEMD wavelet threshold denoising algorithm was 2.42%.The single yield with location information in the farm field was generated by the sunflower seed flow sensor and GPS positioning module,and the single yield data and GPS data were imported into the special yield plotting Surfer software to generate a spatial distribution map of sunflower yield with location information to directly understand the yield distribution of sunflower seeds in a visual way.