# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 3 Research Status of Seedling Picking Mechanism
### Gripper Type
[104; 105] proposed a series of non-circular-gear train picking mechanisms for vegetable transplanting, optimizing structural parameters via human-machine interaction, modeling under optimal parameters, and achieving mechanical seedling picking. [PERSON] et al. [106] developed a novel rotary plug-seeding picking mechanism (Figure 13a). Based on its structural and operational principles, three transmission ratio functions were selected to derive a new non-circular gear's pitch curve equation. A kinematic model was established, and parameters meeting operational requirements were obtained through human-machine interaction. Virtual simulation verified the mechanism's feasibility and operational smoothness. [PERSON] et al. [107] proposed a planetary gear train rotary picking mechanism (Figure 13b) driven by a combination of partially variable eccentric circular gears and non-circular gears. Parameter optimization via human-machine interaction yielded a high picking success rate. [PERSON], [PERSON], [PERSON] et al. [108; 109; 110] optimized non-circular-gear train parameters, designing various planetary gear train extractors to reproduce the trajectories and postures required for crop plug transplantation. The team of [PERSON] [113; 114; 115] from Jiangsu  
Figure 12: Slide-type Seedling Transplanting Mechanisms. (**a**) Five-link slideway-type seedling picking mechanism [93]. (**b**) Drank slideway-type seedling picking mechanism [96]: 1. automatic control system; 2. seedling cups; 3. seedling clamping device; 4. seedling transporting device; 5. seedling air loosening device; 6. air compressor; 7. fixed frame. (**c**) Fully Automatic Slide-Type Dryland Seedling Transplanting Mechanism [99]: 1. Slideway; 2. Slideway base plate; 3. Drive flange; 4. Drive shaft; 5. Crank; 6. Guide wheel; 7. Crank arm; 8. Crank arm shaft; 9. Planting arm; 10. Clamp plate; 11. Finger-clamp rod; 12. Finger-clamp opening arm; 13. Planting-arm base plate; 14. Finger-clamp opening guide plate. (**d**) Combination seedling picking mechanism [100]. University researched non-circular-gear train extractors, developing effective mechanisms like the probing-type chili extractor (Figure 13c). [PERSON] et al. [116] designed a planetary gear train extractor with non-circular complete gears and a large seedling-pushing angle, meeting vegetable transplanting requirements (Figure 13d). In addition to purely mechanical gripper-type automatic seedling picking mechanisms, many scholars have proposed various gripper-type automatic picking mechanisms with mechatronic-hydraulic-pneumatic integrated control. [PERSON] [117] designed a seedling picking device based on mechatronics, effectively reducing energy loss and improving extraction efficiency during operation. [PERSON] [118] developed a gripper-type vegetable transplanting robot, which uses a PLC control system to regulate the opening/closing of the picking mechanism and seedling placement. It primarily performs transplanting in protected agriculture but exhibits low operational quality. [PERSON] et al. [119] designed a double-row seeding picking device and control system (Figure 14), reducing seedling pot damage by coordinating lifting and clamping cylinders. [PERSON] et al. [120] developed a mechanical-electric seedling picking device for greenhouse transplanting (Figure 15), achieving a maximum seedling transplanting success rate of 95.47%. Figure 13: Non-circular planetary gear train seedling picking mechanism. (**a**) Rotary Plug-Seedling Picking Mechanism [106]: 1, 10. Seedling picking claws; 2, 9. Planetary gears; 3, 7. Intermediate gear-1; 4, 8. Intermediate gear-2; 5. Planetary carrier; 6. Sun gear; 11. Plug-seeding tray. (**b**) Rotary plug-seeedling pick-up mechanism [107]: 1. Planetary gear train; 2. Motion trajectory; 3. Seeding pick-up arm; 4. Plug-seeedling tray. (**c**) Penetrating chili seedling picking mechanism [114]: 1. Non-circular Central Gear; 2. Planet Carrier; 3. Non-circular Planet Gear II; 4. Picking Arm II; 5. Picking Arm I 6. Seedling; 7. Plug Tray; 8. Trajectory; 9.