To fill the research gap in the mechanical and physical properties of different varieties of sweet potatoes at different points in the harvest period and to provide a theoretical basis for the design of key components of the sweet potato harvester, the physical properties of Su-Shu 16, Su-Shu 36, and Ning-Zi 4 during the harvest period were studied at three time points: 15 October, 25 October, and 4 November 2023. The moisture content of sweet potatoes was determined using the DGF30/7-IA electric hot air-drying oven. The results showed that the moisture content of sweet potatoes decreased with increasing growth time at three different time points during the harvest period. The moisture content of Su-Shu 16 was, on average, 12.74% higher than that of Su-Shu 36, while the moisture content of Ning-Zi 4 was, on average, 8.07% higher than that of Su-Shu 36. The density of Su-Shu 36 measured by the drainage method is greater than that of Su-Shu 16 and Ning-Zi 4, but the difference is relatively small, and the density tends to decrease slowly with the increase of growth time. Using an electronic universal testing machine, compression tests were conducted on Su-Shu 16, Su-Shu 36, and Ning-Zi 4 at loading speeds of 5 mm/min and 10 mm/min, respectively. The results showed that the compressive strength limit range of Su-Shu 36 was slightly higher than that of Su-Shu 16 and significantly higher than that of Ning-Zi 4. The Poisson’s ratio, elastic modulus, and shear modulus values of Su-Shu 16 and Su-Shu 36 were similar and much higher than those of Ning-Zi 4. Studying sweet potatoes’ growth and physical characteristics for different purposes can provide data references for the design of digging depth, working width, and conveyor chain gap of sweet potato harvesters, as well as data references for sweet potato simulation experiments.

With the advancement of technology and the national effort to promote the development of agricultural mechanization, sweet potato harvester technology is continuously evolving. To solve the problems related to high skin breakage rates and high damage rates during sweet potato harvesting, it is necessary to develop a conveying and separation mechanism that facilitates low skin breakage rates, low injury rates, good potato–soil separation, and smooth transport. This paper elaborates on the working modes of mechanized sweet potato harvesting, focusing on the current state of research on the conveying and separating mechanisms of sweet potato harvesters both in China and elsewhere. The functions of different types of conveying chains are summarized, the conveying and separating technologies used for the mechanized harvesting of other root crops that can be applied to sweet potato harvesters are analyzed, and an outlook on the development trends regarding sweet potato harvesters is provided.

During the mechanized harvesting process, fresh sweet potatoes are prone to damage, which affects their marketability; meanwhile, incomplete separation of potato tubers from the soil also reduces harvesting efficiency. This study employs the EDEM discrete element method to model and simulate the conveying and separation mechanism of the 4UZ-80 lightweight fresh sweet potato combine harvester, investigating the effects of key parameters on damage rate, skin breakage rate, and soil content. Simplified models of the mechanism, sweet potato particles, and soil particles were created using Inventor software, and the interactions among sweet potatoes, soil, and conveying chain rods during transport were simulated on the EDEM platform. The research focuses on the influences of conveying speed, conveying angle, and material generation speed on the forces acting on sweet potatoes and the efficiency of soil separation. Simulation results indicate that when the primary lifting chain operates at 0.45 m/s, with a conveying angle of 30° and generation speeds of 500 g/s for sweet potatoes and 2000 g/s for soil, the compressive force on the sweet potato particles is relatively low, while the soil proportion decreases from 77.92% at 0.2 m/s to 69.81% at 0.45 m/s, and further to 64.50% at 0.7 m/s. Moreover, increasing the conveying angle from 25 to 35° reduces the soil content from 75.49 to 64.38%, suggesting that a larger angle improves soil separation, although it increases the forces on sweet potatoes at the junction. Adjustments in material generation speed reveal that too low a speed leads to direct collisions on the sweet potatoes, whereas too high a speed exacerbates forces due to soil accumulation; both conditions significantly affect the separation outcome. Under the conditions of conveying speed of 0.45 m/s, conveying angle of 30°, and working speed of 0.25 m/s, the rate of sweet potato injury is about 0.84%, the rate of peeling is about 0.74%, and the soil content is 70.94%, which is consistent with the simulation results. These findings demonstrate that the EDEM discrete element method offers high predictive accuracy for optimizing the parameters of the conveying and separation mechanism, providing effective theoretical and technical support for reducing sweet potato damage and improving separation efficiency.

When sowing with a wide boundary under full rice straw retention in the rice–wheat rotation area of China, conventional fertilization methods have some problems, such as a low fertilizer utilization rate, heap soil around a buried fertilizer device, or blocked fertilizing orifice. Firstly, combined with theoretical analysis, discrete element numerical simulation technology, and central composite test method, the wide-boundary fertilization device for wheat wide-boundary sowing was designed. Then, with the coefficient of variation for particle uniformity (CVPU) as the response value, the central composite experiment was carried out on the key structural parameters (focal length coefficient, lateral span, tilt angle, and ground clearance) of the wide-boundary fertilization device by EDEM software. Finally, the influential rules of core factors of the device on the CVPU were analyzed by Design-Expert software; then, the optimal parameter combination was determined and verified by a field test. The results showed that all factors had significant effects on the CVPU. The primary and secondary factors affecting the CVPU were the tilt angle, lateral span, focal length coefficient, ground clearance, tilt angle × ground clearance, and lateral span × ground clearance, in which there were certain interactions between the tilt angle and ground clearance and lateral span and ground clearance. When the focal length coefficient, lateral span, tilt angle, and ground clearance were 1.5, 60 mm, 30°, and 192 mm, respectively, the lateral was minimum. In this case, the theoretical value and field test value were 14.11% and 17.63%, respectively. The field test value is consistent with the theoretical calculation value. This study could provide references for the design of a fertilizer-spreading device with a wide boundary.

China’s orchards cover vast areas, predominantly located in hilly regions where the terrain is complex, making mechanized operations difficult to implement effectively. This results in a low comprehensive mechanization rate in the fruit planting industry, severely restricting the development of agricultural mechanization in China’s hilly areas. This article first explains the principles of automatic leveling technology, summarizing the characteristics and suitable application scenarios of different leveling technologies in the context of actual work in hilly orchards. It then provides an overview of the research progress in automatic leveling machinery for orchards from the perspectives of power machinery, operation platforms, and operating tools, analyzing the leveling control schemes of various orchard operation machinery equipped with automatic leveling features tailored for hilly orchard work. This article explores key technologies for chassis leveling, summarizes universal leveling mechanisms and control algorithms, analyzes the numerous challenges faced by the current development of automatic leveling technology for orchard machinery, and offers targeted development suggestions.

To address issues such as attitude instability, insufficient adaptability, and poor operational quality of precision operation equipment caused by complex terrain conditions in hilly orchards, this study designed an electric carrier Self-Leveling Platform based on the 3-RRS parallel configuration. Focusing on the stability requirements of the operation plane, an automatic leveling control strategy was proposed with the constant center height of the moving platform as an additional constraint condition. Based on the inverse kinematics solution of the 3-RRS Parallel Mechanism, the analytical mapping relationship between the fuselage attitude and the compensation angle of the leveling leg crank was derived, and based on this, the working space of the Self-Leveling Platform and the maximum compensation angles of the moving platform in the pitch and roll directions were calculated. Key structural parameters were optimized using a multi-objective genetic algorithm, followed by the completion of a 3D model design and modal simulation analysis to verify the effectiveness of the structural design. Finally, leveling performance tests were conducted on a prototype. The results showed that the platform can achieve omnidirectional automatic leveling, with a maximum leveling time of 1.593 s and a maximum steady-state error of 0.62° under typical slope and load conditions. Analysis of variance results further indicated that there are significant differences in the leveling performance of the 3-RRS parallel configuration of the Self-Leveling Platform in the pitch and roll directions, demonstrating anisotropic characteristics. This study provides an effective solution for attitude stability control of orchard operation equipment in hilly areas and offers theoretical reference and technical support for the application of the 3-RRS parallel configuration in the agricultural equipment field.