In order to improve the screening performance and cleaning effect of the jujube harvesting machinery cleaning device, a vibrating curved screen device was designed in this study. By analyzing the structure mechanism of the curved sieve body, it was obtained that the arc-shaped mesh hole spacing S was 15-25 mm and the curved mesh hole curvature U was 90°-150°. By exploring the movement state and stress of jujube and impurities on the curved sieve body, it was determined that the horizontal spacing L of the curved layer sieve was 30 mm and the vertical spacing H was 45-65 mm. Taking the vertical spacing H of the curved layer sieve, the curvature U of the curved mesh hole, and the spacing S of the curved mesh hole as the experimental factors, considering the screening efficiency α and the impurity content β of the jujube as the response values, the three-factor three-level quadratic regression orthogonal experiment was designed, establishing the regression mathematical model of each factor and response value, and the multiple target optimization algorithm of Design-expert software was used to optimize various factors. The results showed that the influence factors on the screening efficiency were in the descending order as: the arc screen spacing, the vertical spacing of the curved layer screen, and the curved screen hole curvature; The significant factors affecting the impurity content of jujube were in the descending order as: the arc screen spacing, the curved screen hole curvature, and the vertical spacing of the curved layer screen. The experimental results were verified by the optimized combination of parameters: when the vertical spacing H of the curved layer screen was 65 mm, the curved screen hole curvature U was 110°, and the arc screen spacing S was 23 mm, the average screening efficiency α in the test was 91.09%. The relative error between the experimental verification value and the theoretical optimization value was 1.36%, which was less than 5%. The impurity content of jujube β in the test was 1.02%. The relative error between the experimental verification value and the theoretical optimization value was 2.00%, which was also less than 5%. The test results can provide a reference for the research and optimization of the subsequent air-suction-type jujube harvester cleaning device.

Spinach products in China have constituted over 90% of global output in recent years. Among them, root-cutting into the soil has been the sole harvesting method, in order to fully meet the national needs of large-scale production. It is very necessary to reevaluate the existing interaction models among spinach roots, soil, and cutting implements during harvesting. Current root-soil complex models cannot consider the influence of fibrous roots on the mechanical properties during root cutting, leading to the imprecise parameters of calibration. In this study, a discrete element model was presented to simulate the actual growth of spinach. A comparative framework was then established to analyze the scenarios both with and without fibrous root representations. A systematic analysis was implemented on the external dimensions of spinach taproots, the growth angles, and the distribution characteristics of fibrous roots in the soil matrix. A complete soil model was established using the discrete element method, including taproots and fibrous roots. A series of tests were conducted, including taproot accumulation, shear testing of the taproot, tensile testing of fibrous roots, and soil accumulation. The intrinsic, contact, and governing parameters were calibrated to determine the interactions between spinach roots and the soil medium. Calibration results demonstrated that the relative errors of simulation and measured average values in the taproot repose angle and ultimate shear force were 0.23% and 0.98%, respectively. Similarly, the relative error for the ultimate tensile force of fibrous roots was recorded at 0.9%, while the soil repose angle exhibited a relative error of 0.18%. A discrete element model of the spinach root-soil complex was then established using calibrated parameters. A validation test was conducted for the ultimate shear force within this complex. Single-factor testing revealed that the ultimate shear force escalated with the increase in the static friction coefficient and the bond radius coefficient between the root and soil within the specified range of factor values. Conversely, there was an initial increase followed by a decrease in response to the rising values of the rolling friction coefficient, normal stiffness per unit area of the bond, critical normal stress, and the contact radius coefficient of soil particles. Notably, the shear stiffness per unit area of the bond between roots and soil particles shared a negligible influence on the ultimate shear force. While the critical tangential stress also exerted a minimal but non-negligible effect. Box-Behnken response surface optimization indicated that the significance of influencing factors on the ultimate shear force was ranked in the descending order of the critical normal stress of the bond, static friction coefficient between spinach roots and soil, bond radius coefficient, rolling friction coefficient between roots and soil, soil particle contact radius coefficient, and bond unit area normal stiffness. The relative error of ultimate shear force between the optimized and measured values was recorded as 0.44%, indicating the high accuracy and reliability of the spinach root-soil complex model. The mechanical characteristics were effectively captured in the root cutting during spinach harvesting. The comparative analysis was also made on the root cutting characteristics-contrasting scenarios with/without fibrous roots. It was found that the ultimate shear force of the root-soil complex without fibrous roots was approximately 11.4% lower than that of the complex inclusive of fibrous roots. Moreover, the relative displacement between the main root and the soil increased by roughly 40.3%. It infers that the fibrous roots were used to bind the soil and then stabilize the taproot. The accuracy of the simulation was also enhanced by the spinach root system model. These findings can also provide a strong reference to facilitate the interaction dynamics among spinach roots, soil, and cutting tools.