Optimization design of a double planet carrier planetary gear train transplanting mechanism based on an MBD–DEM simulation of potted plant movement

Abstract

To design a simple and efficient flower transplanting mechanism, a thorough analysis of the potted plant cultivation process was conducted, and methods for designing the mechanism based on the posture constraints during the seedling retrieval and planting phases were investigated. A multidegree-of-freedom-driven virtual end-effector system was constructed. On the basis of the MBD-DEM analysis of the planting process for potted plants, a comparative analysis was conducted on the planting effects of the ordinary shovel, V-shaped shovel blades, and the bionic shovel under the same motion parameters. The bionic shovel was chosen as the structural form of the end-effector. Through parameter simulation optimization analysis of four factors, namely, the attitude angle of the end effector at the entry point into the soil and at the deepest planting point, the length of the hole, and the lateral planting distance, a set of motion parameters for the end effector was subsequently determined. This set of motion parameters was then translated into kinematic parameters for mechanism design; specifically, the length of the hole was 40 mm, the planting depth was 55 mm, the attitude angles of the seedling needle fixed at the entry point into the soil and at the deepest planting point were $130°$ and $82°$, respectively, and the lateral planting distance was 8.6 mm. These parameters serve as the basis for the mechanism design posture. On the basis of the characteristics of a single-row two-stage noncircular gear transmission set, a design method for the double planetary gear train transplanting mechanism was proposed to address mixed postures. This method involves variables such as the rotation angle of the sun gear, the rotation angle of the middle gear, the length of each rack and the initial installation angle of each rack. The objective is to minimize the deviation between the actual position and the target position of the end-effector while ensuring the transmission performance of the noncircular gearset. The motion parameters obtained from the simulation results were converted into kinematic parameters for mechanism design, completing the design of the flower transplanting mechanism. A potted plant cultivation test bench was constructed, and potted plant cultivation experiments were conducted. The average planting rate reached 85.94 %, validating the effectiveness of the planting motion analysis results based on virtual simulation technology. These results demonstrate the practicality of the designed flower transplanting mechanism.