# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 3 Research Status of Seedling Picking Mechanism
### Ejector Type  
The ejector-type seedling picking mechanism primarily uses an ejector rod to push plug seedlings out of the seedling tray onto the conveyor belt, completing the extraction operation. This structure is simple and features high extraction efficiency. [PERSON] et al. [77] developed an ejector-type extraction device with mechatronic control, while [PERSON] et al. [87] designed a similar device (Figure 11a). Through motion analysis, they determined the optimal extraction point, horizontal movement distance of plug seedlings,  
Figure 10: Fully Automatic Carpet-Seeding Transplanter. (**a**) 2 ZY-6 Rapseeed Carpet-Seedling Transplanter [40]. (**b**) Rape Blanket Seedling Combined Transplanter [85]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Seedling Picking Methods** & **Main Implementation Forms** & **Advantage** & **Disadvantage** \\ \hline \multirow{4}{*}{ ejector-type} & \multicolumn{2}{c}{Crank-sider type} & \multicolumn{2}{c}{Camb profile contact prone to wear.} & \multicolumn{2}{c}{Requires multimechanism coordination.} \\  & \multicolumn{2}{c}{Schr seedling ejection stroke.} & \multicolumn{2}{c}{Complex mechanical transmission.} \\  & \multicolumn{2}{c}{Servo push-rod type} & \multicolumn{2}{c}{Compact structure, fast speed, and low} & \multicolumn{2}{c}{Low efficiency and high cost.} \\  & \multicolumn{2}{c}{Pneumatic type} & \multicolumn{2}{c}{High automation level, high seedling} & \multicolumn{2}{c}{Require precise coordination of various} \\  & \multicolumn{2}{c}{Pneumatic type} & \multicolumn{2}{c}{Picking efficiency.} & \multicolumn{2}{c}{mechanisms and complex control.} \\  & \multicolumn{2}{c}{Slide-way type} & \multicolumn{2}{c}{Capable of achieving complex seedling} & \multicolumn{2}{c}{Prone to wear and tear, high vibration,} \\  & \multicolumn{2}{c}{Splice structure, low cost, easy to process} & \multicolumn{2}{c}{and impact.} \\  & \multicolumn{2}{c}{Multi-link type} & \multicolumn{2}{c}{Simple structure, low cost, easy to process} & \multicolumn{2}{c}{High mechanical inertia force, leading to} \\  & \multicolumn{2}{c}{Multi-link type} & \multicolumn{2}{c}{and manufacture.} & \multicolumn{2}{c}{Low seedling extraction efficiency.} \\  & \multicolumn{2}{c}{Linear slide table type} & \multicolumn{2}{c}{High seedling selection precision.} & \multicolumn{2}{c}{Low targeting efficiency, mainly} \\  & \multicolumn{2}{c}{Complex of arranging multiple seedling} & \multicolumn{2}{c}{Capable of arranging multiple seedling} & \multicolumn{2}{c}{Challenging design and manufacturing of} \\  & \multicolumn{2}{c}{Planetary gear type} & \multicolumn{2}{c}{extraction arms, featuring high extraction} & \multicolumn{2}{c}{non-circular gears.} \\  & \multicolumn{2}{c}{efficiency and smooth motion.} & \multicolumn{2}{c}{Simple structure, low cost,} & \multicolumn{2}{c}{Only applicable for small seedlings.} \\  & \multicolumn{2}{c}{Mechanical press-down type} & \multicolumn{2}{c}{Strength, low seedling damage, and} & \multicolumn{2}{c}{High energy consumption. Difficult to} \\  & \multicolumn{2}{c}{Negative-pressure type} & \multicolumn{2}{c}{missing rate.} & \multicolumn{2}{c}{maining good sealing.} \\  & \multicolumn{2}{c}{Air-blowing type} & \multicolumn{2}{c}{No rigid mechanism acting on} & \multicolumn{2}{c}{Low seedling extraction success rate and} \\  & \multicolumn{2}{c}{plug seedlings.} & \multicolumn{2}{c}{high energy consumption.} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Implementation forms and characteristics of automatic seedling picking methods. and conveyor belt advance during extraction, addressing issues like uncontrollable seedling trajectory and poor placement consistency in automatic transplanter extraction systems. However, this method exhibits a relatively high growing medium fragmentation rate for plug seedlings. To reduce the growing medium fragmentation rate while enhancing seedling picking success and qualification rates, researchers have proposed ejector-gripper combined seedling picking mechanisms. [PERSON] et al.