Vegetables have been the second largest cultivated crop after grain in China, among which leaf vegetables account for 25% of the total planting area of vegetables. Among them, seedling transplanting is one of the most important steps during planting. Automatic transplanting can be expected as an effective way to fully meet the requirement of single-plant planting of leafy vegetables. However, it is still lacking in the automatic transplanting equipment of leaf vegetables, particularly on the reliability. Two challenges remain in the application of the automatic transplanter in leafy vegetables: first, the sending and dividing seedlings are suitable for long-stem seedlings of solanocarps with developed roots, rather than broad-leaved and short-stem leafy vegetables. Second, the high accuracy of sending and dividing seedlings can lead to the low reliability of the machine and the planting efficiency. Therefore, it is urgent to explore raising seedlings, conveying and separating suitable for the automatic transplanting of leafy vegetables, in order to improve the mechanical planting level of leafy vegetables. In this study, a combined conveying and separation device was designed with the conveyor belt and stop pin for the cabbage substrate block seedlings, particularly for the high success rate and low injury rate of automatic conveying and separating of leafy vegetables. Combined with the mechanical properties of cabbage substrate block seedlings, the theoretical analysis was carried out to determine the stable conveying and separating conditions of the conveying and separating device and the working parameters of the key mechanism. The test bench was built for the single-factor test to determine the range of key factor parameters. The front conveyor belt motor speed, rear conveyor belt motor speed, and frequency of the stop pin were selected as the main test factors. The Box-Behnken central composite test was carried out with the success rate of seedling separation and the substrate block breakage rate as the evaluation indexes. The second-order regression model was established to clarify the influence of various influencing factors on the indexes. The results showed that the better performance of conveying and separating was achieved, when the motor speed of the front conveyor belt was 104 r / min, the motor speed of the rear conveyor belt was 75 r/min, and the frequency of the stop pin was 1.85 s per time. The success rate of seedling separation was 92.73%, and the damage rate of the substrate block was 4.09% in the bench verification test. The success rate of seedling separation was 91.81% and the damage rate of the substrate block was 4.62% in the field verification test. The error values of the two verification tests and the optimization were less than 2 percental points, indicating the high stability. This finding can provide a strong reference for the design of automatic vegetable transplanting equipment.

Aiming at the problems of low success rate and high seedling injury rate of automatic vegetable transplanting, this study focused on cabbage substrate block seedlings and developed a progressive push-out automatic seedling device controlled by a PLC system. Based on the friction mechanical properties of seedlings-tray during seedling taking, the collision rebound theoretical analysis of substrate block seedling delivery and the finite element simulation analysis of the seedling taking mechanism were carried out to determine the conditions for stable seedling taking and delivery of the device and the working parameters of the key mechanisms. To evaluate individual parameter effects, a test bench was built, and the effective ranges of key factors were subsequently determined. Three key experimental factors, the inclination angle of the limit guide plate, the seedling separation channel width, and the seedling separation cylinder pressure, were investigated using an L9(3⁴) orthogonal array design with blockage rate and breakage rate as evaluation metrics. The range and variance analysis methods were employed to determine the relative significance of each factor’s influence on the performance indicators. The optimal parameters were determined as: the inclination angle of the limiting guide plate was 3.5°, the width of the seedling separation channel was 50 mm, and the pressure of the seedling separation cylinder was 0.6 MPa. Under these conditions, the seedling taking effect was significantly improved: the blockage rate was 2.46%, the breakage rate was 3.18%, and the seedling taking success rate was 94.36%. The optimal parameter combination was verified by the experiment: the average blockage rate was 3.23%, the average breakage rate was 3.68%, and the average success rate was 93.09%. Compared with the orthogonal experiment, the relative success rate error was 1.27%, indicating that the device has high stability. This study will provide a reference for the design of automatic vegetable transplanters.