In order to further clarify and improve the working performance of separating cleaning device of flax threshing material, and study the motion law and characteristics of components of flax threshing material, in this paper, numerical simulation was carried out on the separating cleaning process of flax threshing material based on CFD-DEM method. Simulation results showed that the components of flax threshing material were separated and cleaned under the influence of airflow field, meanwhile, variation curves of quantity and mean velocity of flax seeds in the separating cleaning system were obtained. By referring to streamline distribution of gas-solid coupling, the quantity variation law of components of flax threshing material with time was explored and their motion curves and variation tendency of average velocity were studied. Verification test results showed that the cleaning rate of separating cleaning device for flax threshing material was 92.66% with 1.58% of total separation loss. Compared with simulation results, the test results were 1.34% and 0.93% lower, showing that it is feasible to apply the gas-solid coupling theory and method to simulate the separating and cleaning operation of flax threshing material.

Autonomous navigation for agricultural machinery has broad and promising development prospects. Kalman filter technology, which can improve positioning accuracy, is widely used in navigation systems in different fields. However, there has not been much research performed into navigation for sprinkler irrigation machines (SIMs). In this paper, firstly, a self-developed SIM is introduced. Secondly, the kinematics model is established on the platform of the self-developed SIM, and the updated Sage–Husa adaptive Kalman filter, which is an accurate and real-time self-adaptive filtering algorithm, is applied in the navigation of the SIM with the aim of improving the positioning accuracy. Finally, experiment verifications were carried out, and the results show that the self-developed SIM has good navigation performance. Besides this, the influence of abnormal observations on the positioning accuracy of the system can be restrained by using the updated Sage–Husa adaptive Kalman filter. After using the updated Sage–Husa adaptive Kalman filter for the SIM, the maximum deviation between the SIM and the predetermined path is 0.18 m, and the average deviation is 0.08 m; these deviations are within a reasonable range. This proves that the updated Sage–Husa adaptive Kalman filter is applicable for the navigation of sprinkler irrigation machines.

The coefficient of rolling friction is a foundation parameter for conducting particles simulation, however, which of irregularly shaped maize seeds is difficult to measure. Furthermore, the coefficient of rolling friction between the simulation particles and the actual seeds is inconsistent due to the shaped difference of model and different position of gravity center. This paper use two methods to determinate the coefficient of rolling friction based on discrete element method (DEM) and physical experiments. Three types of maize models from five different shaped maize samples (including horse-tooth shape, spherical cone shape, spherical shape, oblate shape, irregular shape) were developed with the help of slice modeling and 3D modeling technology. Aluminum cylinder container is used to arrange the simulation experiments of angle of repose with taking the coefficient of rolling friction as independent variables and the simulation angle of repose as target values. After predicting detailed the coefficient of rolling friction (including horse-tooth shape, spherical cone shape, spherical shape, between horse-tooth shape and spherical cone shape, between horse-tooth shape and spherical shape, between spherical shape and spherical cone shape maize models), and forecasting a unified the coefficient of rolling friction among horse-tooth shape, spherical cone shape and spherical shape maize models, two types of materials (aluminum cylinder container and organic glass container) were used to validate the difference the angle of repose between the simulation maize models and actual maize seeds. Results show the relative error of the angle of repose between the maize models controlled by the coefficient of rolling friction through the detailed method and the actual maize seeds is 0.22%, 0.33% in aluminum cylinder, organic glass container, respectively. The relative error of the angle of repose between the simulation maize models controlled by the coefficient of rolling friction through the united method and actual maize seeds is 2.47%, 2.97% in aluminum cylinder, organic glass container, respectively. Although the difference of the angle of repose between two method is smaller, the detailed method is better. Moreover, From the accumulation process of the angle of repose we found that the difference on the contacts number between maize models and bottom plate, the change curve of the rotational kinetic energy, the potential energy of maize models controlled by the coefficient of rolling friction through the detailed and the united method are evidently. We can choose a better method to predict the coefficient of rolling friction of maize seeds according to the application situation and investigation objective of irregular maize seeds. The results can provide a theoretical basis for designing and optimizing the structure of the seed-metering machine with DEM.

In order to realize seedbed mechanization of whole plastic-film mulching on double ridges and to overcome the difficulty in crosswise belt type soil covering by whole plastic-film, a kind of crosswise belt type whole plastic-film ridging-mulching corn seeder on double ridges was designed in this study. The key components of the sample machine was designed and its working parameters of seedbed soil covering device, crosswise-belt soil covering mechanism and profiling sowing depth adjustment device were determined. After numerical simulation on the film edge and crosswise soil covering by whole plastic-film on double ridges by discrete element method, the velocity and displacement of the oscillating plate, and the variation rule of amount of covered soil with time were explored. Field test results show that, when the advancing velocity of the machine was 0.50 m/s, the qualified rate of soil width covered on film edge of the seedbed reached 96.1%, qualified rate of crosswise soil belt width was 94.5%, qualified rate of soil thickness on seedbed was 95.3%, qualified rate of sowing depth was 89.3%, qualified rate of spacing between crosswise soil belts reached 93.6%, which all met related standards in China and satisfied design requirements, and could realize seedbed mechanization of whole plastic-film mulching on double ridges. Comparison tests on working performances of practical soil covering show a basic consistence with the seedbed soil covering simulation, and verified the effectiveness of the soil covering model built by using discrete element method.

Mechanization of field experiments is the only way to improve crop breeding and seed propagation effects. In order to further clarify and improve the working performance of tapered threshing device for plot breeding, and reduce the remaining seeds in the device, the numerical simulation was carried out on the motion process of materials in the longitudinal-axial tapered cylinder threshing and transmission device of the plot wheat breeding combine harvester based on CFD-DEM method. Simulation results showed that, threshing and transmission of particles and short stalks at axial direction could be realized under the influence of air flow. Meanwhile, the material transference and distribution rule and stream field distribution rule of air flow in the threshing and transmission device were obtained, the variations of velocity and displacement of particles and short stalks with time were obtained; the motion trajectories and forms of particles in different types of retention were also studied. At rotating speed of 1300-1600 r/min for the tapered threshing cylinder in the verification test, the particle retention rate in the enclosure was 0-0.13%, while in the simulation the particle retention rate in the enclosure was 0-0.11%, only a 0.02% difference between them. The results proved a favorable feasibility to simulate the working performance of the tapered threshing and transmission device for plot breeding through gas-solid coupling method.