To avoid the issues of undesired soil compaction and seeding depth variation caused by the downforce fluctuation of the corn no-till planter, the influence of the structural parameters of the air spring on the downforce was researched in this paper, by establishing the gas–solid coupling simulation model of the air spring. The downforce test bench was built to verify the simulation model; the test showed that the vertical output force error of the simulation model was 4.79%, the pitch diameter error was 0.76%, and the pressure error was 5.07%. The cord angle, piston angle and piston diameter were used as influencing factors to carry out single-factor experiments. The influences of structural parameters on downforce were analyzed from four aspects: the vertical output force, the vertical stiffness, the pressure difference and the deformation rate. The results showed that the cord angle reduced the effective area and its change rate during deformation by limiting the radial deformation of the bellow. When the cord angles were 30°, 45° and 60°, the deformation rates were 65.6%, 20.3% and 4.8%, respectively. The cord angle had a positive effect on the vertical output force when the cord angle was in the range of 30~56°, and it had a negative impact in the range of 56~60°. As the cord angle increased, the vertical stiffness decreased. As the piston angle increased, the effective area of the air spring decreased, and the change in internal pressure decreased, reducing its vertical output force and stiffness. The piston diameter had little effect on the internal pressure and deformation rate. It increased the vertical output force and stiffness by increasing the effective area. The structural parameters of the air spring had a significant impact on the stability of the downforce; the structure of the air spring should be optimized according to the downforce demand of the corn no-till planter.

This paper established an accurate discrete element for ultrasonic vibration-cutter-soil interaction model to study the interaction mechanism between the soil-engaging component and the soil. In order to reduce the interaction between calibration parameters and improve the calibration accuracy, it is proposed that the soil constitutive, contact parameters, and bonding parameters be calibrated by combining the soil repose angle experiment and the soil resistance experiment of ultrasonic vibration cutting. The study adopts the Hertz-Mindlin (no slip) contact model used in EDEM, to explore soil particle interactions. The central composite design is used to achieve systematic investigation. 3-factor 3-level orthogonal design experiment was employed using the coefficient of restitution, the coefficient of static friction, and the coefficient of rolling friction as key test factors and soil’s repose angle as the response index. Based on the Hertz-Mindlin with bonding contact model, Design-Expert 13.0 software was used to design the Plackett-Burman experiment, the steepest ascent, and the Box-Behnken experiment. With the maximum soil cutting resistance in ultrasonic vibration cutting experiment used as the response value, the adhesion parameters were optimized, and the optimal solution combination was obtained as: Normal Stiffness = 4.635 × 10⁶ N/m, Shear Stiffness = 3.401 × 10⁶ N/m, and Bonded Disk Radius = 2.57 mm. The optimal parameter combinations obtained from the calibration experiments were verified in two ways: ultrasonic vibration cutting and non-ultrasonic vibration cutting. The results showed that the errors between the simulation values and the actual values of the two comparative experiments were less than 5%, and the model calibrated for the three parameters can be used to study the drag reduction mechanism of ultrasonic vibration cutting in soil.

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.

Straw returning has shown great advantages in residue management and soil protection in crop planting systems. Mechanized retention of straw is the primary straw returning method, which can reduce costs and improve efficiency. It is important to increase the chopping quality in the field of straw returning, because poor chopping quality will provoke a series of problems including seeding blockage. Straw chopping pass rate (CPR) is an important indicator to measure the chopping quality. Therefore, the CPR of straw should be improved during the chopping process. This paper introduced a novel maize straw chopping device. With the ground as the support, the maize straw was chopped rapidly in the vertical direction. The key parameters of the chopping device were determined by establishing mathematical models and kinematics simulation analysis methods via ADAMS. The effects of rotational velocity, installation positions of chopping units, and the tractor forward velocity on the CPR of maize straw and soil bulk density (SBD) were examined through the Box–Behnken design method. The test factors were the rotational velocities of the chopping units (RV, 550 rpm, 650 rpm, 750 rpm), the installation distance of the two chopping units (IDTCU, 480 mm, 600 mm, 720 mm), and the velocity of the tractor (VT, 3 km/h, 4 km/h, 5 km/h). The results showed that the maximum CPR value and better value of SBD were obtained under the RV of 610 rpm, the IDTCU of 526.8 mm, and the VT of 3.96 km/h. Finally, field validation experiments were conducted under the RV of 610 rpm, the IDTCU of 550 mm, and the VT of 4 km/h. The results showed that the CPR of maize straw was 92.0%, which was superior to the requirement as stipulated in the National Standards of China (CPR ≥ 85%). In addition, in 0–50 mm and 50–100 mm soil layers, the bulk density was decreased by 25.42% and 13.24%, respectively. These results become of considerable importance for crop production in China.

The collision restitution coefficient (CRC) is the essential parameter of the discrete element method (DEM) to study the interaction mechanism between corn seed and soil. The accuracy of its measurement results is the criticalness to ensuring simulation accuracy. In the current study, the CRC between corn seed and soil is mainly measured by the method of corn seed colliding with soil. However, since the soil is a granular body, the essence of the collision of corn seed with soil is the collision between one corn seed and a quantity of soil particles, resulting in inaccurate measurement results soil particles. Therefore, based on the collision dynamics theory of mass point and fixed surface, this paper proposed a measurement method of CRC to study the interaction mechanism between corn seed and soil. This paper analyzed the influence of mass point selection on the measurement results of CRC in the collision process. The measurement method was determined by taking soil particle as mass point and corn seed as fixed surface. To verify the feasibility of this method, a CRC measurement system was established based on high-speed camera technology. The soil particle was dropped at the heights of 10, 15, 20, and 25 cm to collide with the corn seed. The separation velocity and approaching velocity of the soil particle was measured to obtain the CRC between the corn seed and soil. Taking the CRC as the essential parameter of discrete element simulation, the discrete element simulation experiment (DESE) and the soil bin experiment (SBE)of corn seed free fall impact on soil were carried out, and the experiment results were compared and analyzed. In the experiment, the falling height (40, 50, 60, 70 cm) of corn seed and the touching position of the corn seed (positions a, b, c, d) were taken as the influencing factors. The movement state of corn seed and the separation approaching velocity ratio (SAVR) ξ during the collision were taken as the indexes. The results showed that when the positions of corn seed touched the soil was the same, with the increase of the falling height, the SAVR ξ obtained from the DESE and the SBE showed a downward trend. When the falling height was the same, and the corn seed touched the soil at positions b, c, and d, the motion state in the DESE was basically the same as that in the SBE. The relative error of the SAVR between the DESE and the SBE was less than 10%, which proves the feasibility of the method proposed in this paper. The measurement method of the CRC between corn seed and soil proposed in this study provided a theoretical research basis for clarifying the interaction mechanism between corn seed and soil and solving the seed bouncing in high-speed precision sowing.

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.