Design and experiment of the counter roll seedling taking equipment for rapeseed substrate block seedlings transplanter

High planting frequency and seedling falling stability can be preferred during operations in a seedling-taking device of rape matrix seedling transplanter in recent years. In this study, a counter-roll seedling taking device was proposed for the rape matrix block seedling transplanter. A performance test was also carried out to optimize the structure and working parameters for the stable operation of the roller seedling taking device. A stability analysis was then performed on the seedling taking and planting process, in order to combine with the operating characteristics of matrix block seedling transplanter, according to the requirements of planting agronomy. A single-factor bench test was conducted using the self-developed rape matrix block seedling transplanter, where the rape seedling carrier matrix block was taken as the operation object in the suitable planting period. Subsequently, a systematic investigation was made to clarify the influence of structural parameters on the success and synchronization rate of seedling collection. Specifically, the optimal ranges were achieved, where the seedling carrier angle, the diameter at the bottom end of the roller, and the rotation speed of the roller were determined as 30.0°-34.0°, 25.5-29.5 mm, and 1.8-3.6 r/s, respectively. A three-factor and three-level quadratic orthogonal test was carried out to verify the structural parameters after optimization. The results showed that the performance of seedling collection was the best when the angle of the seedling carrier was 30.7°, the diameter of the roller bottom was 26.4 mm, and the roller speed was 2.2 r/s. Furthermore, the success and synchronization rates of the seedling collection were 94.10%, and 95.14%, respectively, in the bench test. In addition, a high-speed camera was used to extract the trajectory of seedling picking in the rape seedling carrying matrix block at the planting stage, in order to determine the influence of roller diameter on the seedling picking trajectory. Consequently, the average change in the bottom angle of the seedling carrying matrix block during the actual seedling picking was 14.18° under the optimal combination of seedling picking parameters. There was an average angle error of 3.42°, compared with the theoretical value of 17.6°. The variation was attributed to the overall size of the seedling carrier matrix block, and the working vibration of machines and tools in the actual seedling picking. There was also a slight deviation between the bottom angle of the seedling carrier matrix block before and after seedling picking in the theoretical analysis. A field experiment was carried out under a better combination of working parameters, in order to verify the operation performance of the whole machine. It was found that the success and synchronization rate of seedling taking were 89.84%, and 92.01%, respectively, which fully met the performance requirements of the seedling taking device of rape matrix block seedling transplanter. The improved structure can also be optimized in the transplanter seedbed finishing device for better matching with seedling taking device in the follow-up. The finding can provide a strong reference to designing the seedling taking device in a rape matrix block seedling transplanter.