Research on Key Technologies of Planting Machinery and Combine Harvester

Vegetable production machinery has developed considerably over the years. In the modern vegetable production process, agricultural machinery and agronomy have been integrated, resulting in relatively more efficient planting models and operating machinery. To this effect, the unit production cost has been lowered coupled with a simultaneous increase in the production efficiency, thereby bringing considerable benefits to farmers. These advances in technology have not been achieved through a standardized approach, but rather through different approaches spearheaded by different countries around the world. The United States mainly focuses on large-scale operation machinery, while Europe mainly focuses on medium-sized machinery to which effect it has formed a full-scale mechanized production model. Meanwhile, Japan and South Korea mainly focus on small-scale machinery, which has helped to realize the mechanization of certain links in vegetable production but has also caused a lag in terms of production efficiency.

The mechanized production process of vegetable varieties consists mainly of ploughing, furrowing, seeding, and harvesting. Regarding the production process in China, mechanized ploughing accounts for the highest energy consumption. Therefore, there exists an urgent need to reduce ploughing resistance from key machinery components if energy consumption is to be reduced. Additionally, there is a big gap between China and foreign countries in terms of the precision seeding of vegetables; hence, improving the level of mechanized precision seeding is the primary link in a cost-effective and highly efficient vegetable planting process. Mechanized precision seeding technology can greatly improve seeding efficiency, reduce seeding labour intensity, reduce labour costs, save a lot of seeds, and facilitate crop management and harvesting.

Since the 1940s, developed regions such as Europe and the United States have undertaken research on seeders. Grewal R S [1] studied the seeding performance of a six-row inclined disk onion seeder at different speeds and different numbers of slots and tested it in the laboratory with the indicators of replaying rate, miss seeding rate, and qualification rate. The feasibility of the implementation was verified by field experiments. Maleki M R [2] designed a composite screw device to improve the seeding uniformity of a mechanical seeder, and studied the effects of the screw groove depth, width, screw outer diameter, and angular velocity on the seeding effect of the screw device. The optimal combination parameters were obtained through experiments, and the distribution of seeds was detected through uniform coefficients, which solved the uneven phenomenon caused by the pulsation of the seed flow.

However, vegetable seeders in China and abroad are constantly transitioning from the older generation mechanical-type seeders with a single structure to more developed mechanisms with high speeds, generalization, and integration. It should be noted that although foreign large-scale seeders have become increasingly efficient, and are constantly pursuing high speed for large-scale production, they remain largely unsuitable for direct application in China owing to unique conditions characterizing the agricultural landscape.

This field of study focuses on solving the problems of the mechanized production of green leafy vegetables, and it researches and develops complete sets of tillage, ploughing, and planting machinery suitable for the production of green leafy vegetables, as well as the research and development of a vegetable precision seeder. Additionally, the field incorporates research to solve the problem of incompatibility between various machinery and tools in the entire mechanized production of leafy vegetables as well as the agronomic requirements of vegetable production. Through research, this field aims to improve reliability, increase ease of operation, enhance adaptability of equipment through intelligence, reduce labour intensity, and improve the efficiency of vegetable production.

1. Contribution of the Special Issue

The Special Issue “Research on Key Technologies of Planting Machinery and Combine Harvester” presents a collection of ten articles. Wang et al. [3] investigated the pneumatic centralized cylinder direct-seeding metering device to study the effect on the movement phenomena of rice seeds. In total, three suction hole sizes (1.5 mm, 2 mm, and 2.0 mm at 45° wedge) were used for computational fluid dynamics (CFD) simulation. The rice seeds in tube C (maximum angle) presented a movement mechanism comprising of falling in sector a, coupled with further falling after colliding in sector b. The rice seeds in tube B (the second angle) presented a movement mechanism comprising of falling in sector a, coupled with further falling after colliding in sector b.

Li et al. [4] investigated the operating mechanism of a belt-rod type separator of a small-scale, self-propelled potato combine harvester and the separation performance between the tuber and soil. A simulation model based on discrete element method (DEM)-multibody dynamics (MBD) coupling was constructed and single-factor simulation tests were carried out. The authors concluded that in future studies, the simulation model can be further optimized whereby the process of digging and separating could be simulated by considering the excavation shovel and the belt-rod type separation mechanism working together to reduce the error with the field harvest results.

Wang et al. [5] carried out field experiments using a wet direct rice seeder under three driving methods for the seed meter, including a classic mechanical driving system (MDS), an electric driving system with speed acquired from an encoder (EDSE), and an electric driving system with speed acquired from the global positioning system (EDSG). Analysis of the seeding uniformity and slippage showed that the EDSG exhibited a more qualified operation and was recommended for the wet direct rice seeder. Du et al. [6] conducted a bionic optimization design and experiment of reciprocating cutting systems on a single-row tea harvester. Since the structural parameters of the reciprocating cutting systems did not match the tea cut, this resulted in larger cutting resistance. Wang et al. [7] and Sun et al. [8] designed separately a finger clip plate garlic seed-metering device based on EDEM Software and a three-row pneumatic precision metering device for Brassica chinensis. A Box–Behnken experimental design with the qualification index and miss seeding index as the experimental index was used, and the results indicated that the optimal performance of the metering device was achieved.

Zhang et al. [9] investigated the bio-tribological properties of a peanut harvesting impact-frictional contact using a test bench under different conditions. A typical peanut variety, “Dabaisha”, was considered in this study, whereby an orthogonal test with three factors and levels was performed. The apparent morphologies of the peanut shells before and after collision and friction tests were analysed, and results showed that different factors had varying magnitudes of influence on the coefficient of the friction of peanuts and wear loss of peanut pods. Hu et al. [10] developed an attitude adjustment crawler chassis for combine harvesters and experimented with an adaptive levelling system. The design relied on the combination of the attitude detection of the levelling system and adjustment calculation of driving hydraulic cylinders according to the established mathematical models.

Xu et al. [11] analysed and determined key structural parameters of the seeding plate, then established an adsorption mechanics model of the seed during the migration process and designed the key structure of the air-suction seed-metering device intending to improve the uniformity of the high-speed direct seeding of vegetables. Sun et al. [12] estimated the distribution of mature rice plant height based on moving surface and three-dimensional (3D) point cloud elevation. However, dense growth coupled with leafy and bent branches of mature rice crops made it difficult to detect the lowest point of aggregated growing plants in 3D point cloud data.

2. Conclusions

The study of key technologies for planting machinery and combine harvesters is a very important process. The precision sowing technology of planting machinery and the clamping and conveying technology of combine harvesters are among the key factors influencing this process. Therefore, vigorously promoting the application of advanced and applicable planting and harvesting mechanization technologies is a key initiative to achieve agricultural modernization and sustainable development strategies. In summary, the above-mentioned papers show in their conclusions that:

• For crops, precision sowing technology can greatly improve their planting efficiency, with low labour intensity and increased profitability.
• The use of CFD-DEM and DEM-MBD joint simulation technology can simulate the working process of planting machinery, greatly reducing the development costs and waste of resources.
• Combine harvesters combine harvesting and threshing machines in a single unit, allowing farmers to harvest and thresh in a single operation.