To improve the accuracy of discrete element simulation in the process of separating potato–soil mixtures, the contact parameters of sandy soil with 3, 6, 9, and 12% water content were calibrated in DEM simulation using EDEM software simulation. The error of the rest angle between them was used as an index, and the approach of performing only one simulation and multiple Box–Behnken response surface analyses was proposed to determine the optimal parameter combinations. Meanwhile, unconfined compression and direct shear tests were conducted to obtain the parameters of polymer bonds for soil with different water content, and a simulation was carried out using EDEM. The test results show that the significant parameters affecting the rest angle are JKR surface energy, soil interparticle recovery coefficient, and rolling friction factor. The numerical simulation of the rest angle was compared with the physical test, and the maximum relative error between them was 4.72%. The bond parameters of soil with different water content and firmness were obtained and compared with the simulation test, the maximum error was 6.53% for the direct shear test and 8.07% for the unconfined compression test, which proved that the bonding parameters are reliable and provide an effective parametric and theoretical basis for the discrete element simulation of soil particles.

To address the problems of low pickup rates and high rates of wounds in the mechanised harvesting of potatoes under sectional harvesting conditions, a spring-finger potato picker was designed and its overall structure and working principles were described. The kinematic principle of the spring-finger was analysed based on the picking constraints, and the kinematic parameters of the picker were determined. A response surface Box–Behnken Design test design was used to carry out a quadratic orthogonal rotational test, with the speed of the spring-finger, the forward speed of the machine, and the embedded depth as test factors, and the loss rate and the wounded potato rate as evaluation indicators. The test results were optimised and analysed. When the spring-finger speed was 19.57 r/min, the forward speed was 0.61 m/s and the embedded depth was 71.31 mm, the loss rate was 1.18%, and the wounded potato rate was 5.71%. The optimised data were verified, and the results showed that the loss rate of the spring-finger potato picker was 1.48% and the wounded potato rate was 4.98%, meeting the potato picking and harvesting requirements. The research can provide a theoretical basis and design reference for the development and application of sectional potato harvesting machinery.

To study the influence law of the overburden rotating plate mechanism on the fragmentation and separation of potato soil agglomerates, a single-factor test and a response surface test simulation analysis of the soil fragmentation process were conducted in EDEM 2022 software. The results of the single-factor test show that the triangular rack blade of the overburdened rotating plate mechanism has the best effect on soil fragmentation and separation. With the increase in the lower blade speed, the upper lift chain bar line speed, and the tilt angle of the mechanism, the effect on the fragmentation and separation of potato soil agglomerates decreases. The response surface test results show that the debris removal rate decreases with the increase in blade speed and tilt angle, the percentage of bond breakage between potato soil particles declines with the rise of blade speed and lift chain bar line speed, and the percentage of bond breakage between soil particles increases with the increase in blade speed and lift chain bar line speed. The optimal solution was obtained by using the optimization function in Design-Expert 13 software, which was adjusted as follows: the blade rack type was triangular, the lift chain bar line speed was 0.307 m/s, the blade speed was 0.4 m/s, and the tilt angle was 40°. The research methods and results provide a reference for the simulation of potato soil crushing and separation motion in a sandy loam soil cultivation area.

Potato is exposed to different types of impact loads during harvest, sorting, and transportation. The large impact force between potato and rod-shaped machinery parts causes the potato damage and brings economic losses for the food industry. To obtain the impact force and its influencing laws between potato and rod, both theoretical analysis and finite element analysis (FEA) were used. By defining the impact force coefficient (K), a mechanical model between the impact peak force ( $F_{max}$), potato mass (m), and drop height (h) was established. The FEA virtual experiments showed that $F_{max}$ was increased linearly with the increase in m, h, and $m\sqrt{h}$. When the potato mass was from 0.2 kg to 0.35 kg and the drop height was from 0.2 m to 0.3 m, the regression equation between $F_{max}$ and $m\sqrt{h}$ had a similar structure to the mechanical model, which verified the theoretical analysis and allowed the assessment of potato impact force. The results of this article can contribute to predicting the impact force of potato and solving other problems of solid-like agricultural materials related to impact.