Design and test of a seeding mechanism for pre-cut cassava seeding

Cassava cultivation is low-cost and high-yielding, and tubers, stems and leaves can be widely utilized in the food medicine and light industry. However, cassava planting is mainly manual work at present. There is an urgent need to develop precision planting machines suitable for the agronomic requirements of cassava planting. A seeder is the core component of a precision planting machine, including the real-time and pre-cut seed-cutting type. Among them, the real-time seed cutting cannot realize the automatic sowing, due to the long and complicated shape of the cassava seed rods, while the low persistence of manual seed feeding and serious leakage. A seed cutter can be used to cut the cassava seed stems into seed stems of about 150 mm in length in pre-cut seeding. An automatic continuous and controlled seeding of cassava seed stems can be achieved through the seed discharge mechanism after cleaning. The lifting type seed rower has been improved to add the gravity seed cleaning mechanism, while the structure of the clamping plate has been optimized for the seed rowing effect. But the leakage filling still exists so far. Some research has been conducted on the seeders, such as slotted wheels, and single roller types. However, it is very necessary to improve the seed filling performance and qualification index, when seeding cassava seed stems with the existing pre-cut seed sower, because the cassava seed stems are cylindrical woody stalks of a certain length with surfaces of complex physical characteristics. Particularly, the performance of cassava precision seeding needs to be improved, due to a complex process with the multi-factor change. This study aims to improve the seed filling effect and low qualification index of pre-cut seeding type cassava precision seeder. A precision cassava seeding mechanism was designed with pre-cut seeding and friction belt, consisting of seed drop slide, active roller, type hole friction belt, support roller group, driven roller, and seed storage box. The basic structure and working principle of the seed-rowing mechanism were described to determine the parameters of key components. The main factors were then determined with the seed-filling performance of the seeding mechanism, according to the shape, number, installation inclination, and speed of the typed hole on the friction belt, as well as the thickness of the seed stem layer. The discrete element method (DEM) was used to establish a simulation model of the "seed stem group-hole friction zone". The single-factor simulation was realized to clarify the influence of each factor on the seed-filling performance. The optimal combination of factors and parameters was determined after quadratic regression and orthogonal rotational simulation. Taking the installation inclination angle of the seeding hole friction zone, the thickness of the seeding stem layer, and the speed of the seeding hole friction zone as the factors, the mathematical regression model of each factor was established for the evaluation index. The results showed that the influencing factors of the seed filling index and the leakage index were ranked in descending order of the speed of the type hole friction belt, the installation angle of the type hole friction belt, and the thickness of the seed stem layer. The optimal combination of factors and parameters was achieved in the bench test. The seed filling qualification index was 94.13% for the precut cassava-type friction belt precision seeding mechanism, and the leakage index was 3.77% when the thickness of the seed stem layer was rounded to 220-280 mm, the speed of the friction belt was 0.6 m/s, the installation inclination of the friction belt was 45°, the shape of the friction belt was C-shaped and the number of holes was 12. A better performance was achieved, where the seed filling index and the leakage index were 94.13% and 3.77%, respectively. The finding can provide a theoretical reference for the development of cassava precision seeders.