# Research Progress and Future Prospects of Key Technologies for Dryland Transplanters
## 2 Classification of Transplanters
### Fully Automatic Transplanter
#### 2.3.1 Fully Automatic Plug-Seedling Transplanter  
Numerous fully automatic transplanter models employ automatic seedling picking-placing devices in conjunction with planting mechanisms, though their structural configurations and working principles remain fundamentally similar. These transplanters typically comprise a power unit, traveling mechanism, seedling feeding system, seedling extraction mechanism, planting mechanism, and soil compaction device. The primary distinction from semi-automatic transplanters lies in the inclusion of an automatic seedling feeding system and seedling picking-placing system, while the planting mechanism remains consistent with semi-automatic models. During operation, operators manually place plug-seeedling trays at the seedling feeding mechanism. The trays automatically advance to feed seedlings, which are extracted by the picking mechanism and transferred to the planting mechanism. The planting mechanism inserts seedlings into the soil, followed by soil compaction to complete transplanting. For fully automatic plug-seeedling transplanters, in addition to variations in planting devices, the most notable difference lies in the diversity of seedling picking mechanisms, which is elaborated in detail in Chapter 3 of this paper. [PERSON] et al. [75] developed a fully automatic vegetable transplanter, including (1) a robotic control system; (2) a seedling picking mechanism (SPM); and (3) a traveling mechanism (VMS). The SPM is an electromechanically controlled finger-gripper extractor that clamps seedling stems, transports them above the guide tube, and releases them to fall into the furrow opened by the furrow opener under gravity and tube guidance. [PERSON] et al. [76] developed a tractor-towed three-row automatic transplanter with an inclined magazine-type metering device for paper-tube vegetable seedlings. [PERSON] et al. [77] designed another tractor-towed transplanter featuring a seedling ejector, control system, furrow opener, and soil compaction device. Seedlings are ejected into the furrow via a guide tube, followed by soil compaction. [PERSON] et al. [78] reviewed agricultural robots, including transplanting robots. [PERSON] et al. [79] designed a strawberry transplanter for field testing. [PERSON] et al. [80] developed a towed double-row transplanter (Figure 9a) composed of seedling feeder, combing device, ejector-type extractor, plate-turner, conveyor, separator, double-crank five-bar planter, empty tray recycler, and soil compactor, but high-speed operation causes replanting and missed planting issues. [PERSON] et al. [81] proposed a close-planting transplanter for leafy vegetables with a duckbill planting mechanism (Figure 9b). [PERSON] et al. [82] designed a flexible-disk onion transplanter (Figure 9c) using an ejector-gripper extractor: the ejector pushes out pot seedlings, which are gripped, horizontally conveyed, and planted by the flexible disk. [PERSON] et al. [83] developed a side-mounted close-planting transplanter for sweet potatoes (Figure 9d), adopting a single-sided chain-clamp mechanism to enhance transplanting efficiency. Transplanting robots are equipped with reliable, mature navigation systems and automatic transplanting control systems, which enhance their automation level. However, due to the constraints of these complex systems, such transplanting robots are only suitable for transplanting operations in greenhouses with favorable working environments. In field transplanting, designers develop transplanters based on the specific agronomic requirements of crops for transplanting. For example, Reference [81] presents an automatic transplanter designed for vegetable plug seedlings, while Reference [83] describes a chain-clip transplanter developed to meet the special agronomic needs of sweet potato transplanting. Transplanters suitable for field transplanting operations differ not only in their operating methods but also significantly in their power sources.