As a promising and convenient numerical calculation approach, the discrete element method (DEM) has been increasingly adopted in the research of agricultural machinery. DEM is capable of monitoring and recording the dynamic and mechanical behavior of agricultural materials in the operational process of agricultural machinery, from both a macro-perspective and micro-perspective; which has been a tremendous help for the design and optimization of agricultural machines and their components. This paper reviewed the application research status of DEM in two aspects: First is the DEM model establishment of common agricultural materials such as soil, crop seed, and straw, etc. The other is the simulation of typical operational processes of agricultural machines or their components, such as rotary tillage, subsoiling, soil compaction, furrow opening, seed and fertilizer metering, crop harvesting, and so on. Finally, we evaluate the development prospects of the application of research on the DEM in agricultural machinery, and look forward to promoting its application in the field of the optimization and design of agricultural machinery.

Potato is one of the most important crops in the world to ensure food security for the world’s fast-growing population. Mechanized planting is crucial for improving production and per unit area yield of potato. To meet the agronomic requirements of potato planting, various types of potato planters have been developed according to the existing differences in geographical environment, cropping system, farm scale, and economic status among different countries and regions. This paper summarizes the research progress and application status of potato planters all over the world. Specifically, the seed-metering devices of potato planters are classified firstly. Then, potato planters are classified into three types: potato planters for manual/animal, two-wheel tractor, and four-wheel/crawler tractor traction. Furthermore, the characteristics of some typical commercial potato planters are discussed. Finally, some suggestions are proposed in order to promote the development of potato planters.

Due to a lack of an accurate model in finite element simulation of mechanized harvesting of wild chrysanthemum, the stem of wild chrysanthemum in the harvesting period is taken as the research object. ANSYS Workbench 19.0 software and LS-DYNA software (LS-PrePOST-4.3-X64) are used to calibrate the finite element simulation model of wild chrysanthemum stem cutting. The stem diameter distribution at the cutting height of the chrysanthemum is obtained. The maximum shear forces at different diameters (7 mm, 8 mm, 9 mm, 10 mm, and 11 mm) within the cutting range are determined as 120.0 N, 159.2 N, 213.8 N, 300.0 N, and 378.2 N, respectively, by using a biomechanical testing machine and a custom-made shear blade. The Plastic_Kinematic failure model is used to simulate the cutting process by the finite element method. The Plackett–Burman test is employed to screen out the test factors that significantly affect the results, namely, the yield stress, failure strain, and strain rate parameter C. The regression model between the shear force and significant parameters is obtained by central composite design experiments. To obtain the model parameters, the measured values are substituted into the regression equation as the simulation target values. In other words, the yield stress is 17.96 MPa, the strain rate parameter C is 87.27, and the failure strain is 0.0387. The maximum shear force simulation test is carried out with the determined parameters. The results showed that the maximum error between the simulated and the actual value of the maximum shear force of wild chrysanthemum stems with different diameters is 7.8%. This indicates that the calibrated parameters of the relevant stem failure model can be used in the finite element method simulation and provide a basis for subsequent simulations.

Wild chrysanthemum has a high medicinal value. Its mechanized harvest can improve harvesting efficiency, reduce labor costs and improve planting benefits, which is an important way to promote artificial planting. However, one of the difficulties in mechanized harvesting is the large diameter and hardness of the stem, leading to high cutting resistance and power consumption. In order to reduce cutting resistance and power consumption, a bionic cutting blade is designed in this paper by employing the bionics principle and the contour of the cricket’s upper jaw incisor lobe instead of the sharp triangular teeth of the standard harvester blade. Using the finite element method, the cutting-edge angle, cutting angle, and reciprocating speed were taken as test factors. The maximum shear force and power consumption were taken as evaluation indexes. At the same time, the center combination simulation test was carried out to optimize the cutting body and to determine the optimal cutting speed. When the cutting-edge angle was 21°, the cutting angle was 66°, the reciprocating speed was 1.29 m/s, and the maximum shear force and power consumption were minimal. The results showed that the maximum shear force of the bionic cutter was reduced by 18% and the power consumption by 15.8%. The bench test showed that the maximum shear force and power consumption of the bionic cutter were reduced by 10.5% and 10.8%, respectively, when the entire wild chrysanthemum stem was cut. The results can provide a reference for the mechanical harvesting of wild chrysanthemum stems.

Wild chrysanthemum stems are cluttered and their flowers are dense, which makes them difficult to pick. In order to solve this problem, in this study, we designed a kind of opposed roller picking device. It was designed based on an analysis of the mechanical characteristics involved in the picking of wild chrysanthemum. The design focused on an opposed drum picking mechanism. Taking the critical post-collision acceleration as the evaluation metric, a theoretical analysis was conducted on the post-collision motion behaviors of wild chrysanthemum and the roller bow tooth. This study found that the primary factors affecting the picking process are the roller rotational speed, the feeding speed, and the impact angle. Furthermore, simulation experiments confirmed that when the roller rotational speed was 3.73 rad/s and the clamping chain moved at 1.3 m/s, the wild chrysanthemum picking platform achieved a picking efficiency of 87.72%, thereby meeting the corresponding requirements for wild chrysanthemum harvesting. Through bench tests, it was found that, when the roller gap was 100 mm, the roller bow tooth bending angle was 56°, and the feeding rate was 2.1 kg/s, the clean picking rate reached 95.9%, thereby meeting the requirements for wild chrysanthemum harvesting. The development of an opposite roller-type wild chrysanthemum-picking device can provide technical support for the development of wild chrysanthemum picking equipment.