To obtain accurate soil parameters and improve the accuracy of the acoustic-soil discrete element simulation model, we studied the model’s parameter calibration. The simulation test was carried out using the measured acoustic velocity and dominant frequency as the response value (index). Firstly, the Plackett—Burman test scheme was used to obtain the sensitivity ranking of soil parameters to the dominant frequency and velocity of the acoustic wave. The parameters that significantly affect the acoustic wave were obtained: Shear modulus, Poisson’s ratio, and coefficient of restitution. Then the Box—Behnken test scheme was used to establish the regression relationship between the dominant frequency and the velocity of the sound wave and Shear modulus, Poisson’s ratio, and Coefficient of restitution. The results shows that the indexes that researchers focus on are different in different scenarios, and the sensitivity of soil parameters to different indicators is different, which results in different soil parameter values after calibration. This study analyzed the main factors affecting the accuracy of the acoustic-discrete element model in constructing the model, provided a method for improving the construction accuracy of the acoustic wave—soil discrete element model and provided a reference for the construction of discrete elements models in other fields.
Aiming at the problems of the poor passing capacity of machines and low cleaning rate of seed strip during wheat no-tillage sowing in annual double cropping areas of North China, a spiral discharge anti-blocking and row-sorting device (SDARD) was designed and is reported in this paper. After the straw was cut and chopped by the high-velocity rotating no-till anti-blocking knife group (NAKG), the straw was thrown into the spiral discharging mechanism (SDM) behind the NAKG. The chopped straw was discharged to the non-sowing area to reach the effect of seed strip cleaning through the interaction between the SDM and the row-sorting of straw mechanism (RSM). Based on a theoretical analysis for determining the parameters of crucial components, the quadratic rotation orthogonal combination test method was adopted, and the operating velocity of machines (OVM), the rotary velocity of the spiral shaft (RVSS), and the height of the holding hopper from the ground (HHHG) were selected as the test factors. The straw cleaning rate (SCR) was taken as the test index. The discrete element simulation test was carried out, the regression model of the SCR was established, and parameters optimization and field test were carried out. The results show that the significant order of the three influencing factors on the SCR was HHHG > OVM > RVSS. The optimal combination of operating parameters was that OVM was 5 km/h, RVSS was 80 r/min, and HHHG was 10 mm. Under the optimal parameter combination, the average SCR was 84.49%, which was 15.5% higher than the no-till planter without the device, and the passing capacity of machines was great, which met the agronomic requirements of no-tillage sowing of wheat in annual double cropping areas. This study could provide a reference for the design of no-tillage machines.
To avoid the issues of seeds lying atop straw, where the seeds cannot germinate, during no-till maize seeding, a seed furrow cleaning device is proposed. The device uses rotating spring teeth and a curved sliding shovel to clear the straw from the seed furrow to the outside. The critical components of the side throwing mechanism, rotary disc and spring teeth design are analyzed, and the value range of the installation inclination angle, rotating speed and bending angle of spring teeth are determined. The force on the straw at the moment of starting to touch and throw it is analyzed theoretically in the three installation directions of forward inclination, radial and backward inclination on the rotary disc, and the backward inclination of the spring teeth is determined. A simulation model of the seed furrow cleaning device is established by using the discrete element method simulation software; the forwarding speed, rotating speed, installation inclination angle, and bending angle of spring teeth are used as influencing factors to carry out single-factor experiments. The influence characteristics of different parameters on seed ditch cleaning effect are analyzed from the aspects of straw cleaning quantity and soil disturbance. A field validation experiment is carried out, and the results show that when rotating speed is 180 r/min, installation inclination angle of spring teeth is 40°, and bending angle is 30°, the straw cleaning rate is 82.26%. The research could provide references to develop the no-till seeder for maize seeding.
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