In response to the pressing issues of unclear adhesion mechanisms during the soil-removal process in peanut harvesting, poor soil fragmentation quality, and difficulties in separating the pods from the soil. Based on TRIZ theory, this study has innovatively designed a separation device that relies on external forces, such as kneading and squeezing. A mechanical model of soil fragmentation and separation was developed. The key factors affecting the device’s operational performance were identified. Through theoretical analysis and discrete element simulation, this study elucidates the working principle by which the device crushes and separates soil particles using kneading and squeezing forces. Through analysis of one-factor and orthogonal experiments, the optimal operating parameter combination for the device was determined to be: a drum installation clearance of 104.7 mm, a rotational speed difference of 75.2 rpm, and a pattern roughness of Grade III (reticulated). The system’s performance metrics are a soil removal rate of 96.59% and a pod damage rate of 2.48%. Field tests have confirmed that the deviation from simulation results is minimal. The device’s performance meets the requirements of actual production.

This study aims to address the major challenges encountered during peanut harvesting and digging in saline–alkali soils, including high digging resistance, poor soil fragmentation, and difficulty separating pods from the soil. A combined cutting–extrusion excavation device was optimized based on soil dynamics. A mechanical model for soil fragmentation via cutting and extrusion was constructed, alongside a mechanical model for separating soil–nut aggregates. Key factors influencing the device’s operational performance were identified, and parameter ranges were determined. Through theoretical analysis and discrete element simulation, the force distribution on the device during operation and the soil fragmentation mechanism were elucidated. Single-factor experiments determined the influence of each factor on evaluation metrics. Through orthogonal experimental analysis, the optimal parameter combination was determined as a blade angle of 21°, a rake angle of 50°, and a forward speed of 4 km/h. At this setting, the number of bonds broken was 172,652, and the working resistance was 14,673.5 N. Field test results indicate that the cutting–extrusion combined excavation device achieved 75.29% soil fragmentation and 16,965.4 N of working resistance. Compared to the original excavation device, soil fragmentation increased by 20.68% and working resistance decreased by 8.06%. The cutting–extrusion combined excavation device outperforms the original excavation device.

Accurate discrete element method (DEM) modelling of mature peanut plants is essential for simulating peanut harvesting, pod detachment, and harvest-loss formation. However, existing peanut DEM models are usually simplified as isolated pods, rigid cylindrical particles, or partial stem–pod structures, which limits their ability to represent the flexible deformation of vines and pod stalks and the fracture behaviors at the pod–pod stalk junction. In this study, a DEM-based flexible plant model was developed for mature peanut plants. The geometric dimensions, contact parameters, and mechanical properties of peanut pods, pod stalks, and stems were measured through physical experiments. The Hertz–Mindlin model was used for non-bonded contacts, whereas the Hertz–Mindlin with Bonding model was adopted to represent the flexible connections among plant organs and the fracture behaviors of the pod–pod stalk junction. The main DEM parameters were calibrated using Plackett–Burman screening, steepest ascent experiments, and central composite design. The results showed that the tangential stiffness per unit area and tangential critical stress at the pod–pod stalk junction were the dominant factors affecting pod detachment force. The optimized parameter combination was a tangential stiffness per unit area of 4.738 × 10⁵ N/m³ and a tangential critical stress of 9.350 × 10⁵ Pa, corresponding to a simulated tensile force of 6.73 N. Model validation was performed by comparing peanut harvesting simulations with field trials. The relative error of pod loss rate between simulation and field measurement was less than 7.55%, and the t-test result indicated no significant difference between the two datasets (p > 0.05). These results demonstrate that the proposed flexible peanut plant model can effectively characterize pod–pod stalk separation and can provide a reliable DEM modelling basis for peanut harvesting process analysis and equipment optimization.