In greenhouse nurseries, one of the important tasks of the automatic transplanter is replanting missing or bad seedling holes with healthy seedlings. This requires the transplanter to spend significant time moving between the supply trays and target trays during replanting. The diversity and complexity of the transplanting routes affect transplanter efficiency. Path planning method can find a better path for the manipulator and improve the efficiency of transplantation. The A* algorithm (A*), which is one of the optimal path search algorithms, is often used in practical applications of path planning. In this paper, the heuristic function of the A* is optimized by the ant colony algorithm (ACA), and an improved A* algorithm (Imp-A*) is obtained. Simulation tests and transplanting trials of Imp-A*, A*, ACA, Dijkstra (DA), and common sequence method (CSM) were carried out using 32-, 50-, 72-, and 128-hole plug trays. The results show that Imp-A* inherits the advantages of A* and ACA in terms of path planning length and computation time. Compared to A*, ACA, DA, and CSM, the transplanting time for Imp-A* was reduced by 2.4%, 12.84%, 11.63%, and 14.27%, respectively. In just six trays of transplanting tasks, Imp-A* saves 60.91 s compared to CSM, with an average time saving of 10.15 s per tray. The combination optimization algorithm has similar application prospects in agriculture.

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Hippophae rhamnoides have yellow or orange berries, which have high nutritional and medicinal value, but it is difficult to harvest directly because of their close attachment to the fruit branches. The vibration harvesting equipment can be designed and developed correctly and reasonably by using the finite element method to study the vibration harvesting dynamics of Hippophae rhamnoides pruning and the parameter design of the related mechanism. First, the 3D model of Hippophae rhamnoides pruning was established by CATIA and was imported into ABAQUS software for modal analysis and harmonic response. The first 12 natural frequencies were determined to be 4.1 ~ 23.1 Hz, the optimum excitation frequency is 21.1 Hz and 16.2 Hz, and the optimum excitation force is 35 N and 25 N respectively. Secondly, the dynamic model of the cutting branch device is established and solved, and after bringing in the relevant parameters, the optimal design dimensions of crank r and connecting rod l are determined to be r1=22mm, l1=88mm, r2=13mm, l2=52mm, respectively. This research can provide a theoretical basis for the development and testing of a vibrating sea buckthorn-cutting harvesting device.

The success rate of automatic transplanter seedling picking is affected by the harsh operating environment of the transplanter and the reduced output accuracy of the opening and closing positioning of the seedling-picking mechanism due to the interference of the external environment. To solve such problems, the paper proposes to use an adaptive fuzzy PID control algorithm as the opening and closing positioning-control system of the seedling-picking mechanism. Based on the theoretical analysis and calculation of the positioning accuracy of the seedling-picking mechanism, a mathematical model of stepper motor angular velocity control was established, and a stepper motor angular velocity control model based on fuzzy PID (conventional PID) control was established in MATLAB/Simulink. In order to further simulate the actual working condition of the seedling-picking mechanism, a simulation model of stepper motor control with disturbance was built, and the response results showed that the fuzzy PID control system could get rid of the disturbance faster under the action of external disturbance signals. The results of the opening and closing positioning test of the seedling-picking mechanism showed that the fuzzy PID control system has higher control accuracy and more stable control performance than the PID control system, which meets the design requirements.