# Design and Test of Seeding-Picking Mechanism of Fully Automatic Transplanting Machine
## 2 Materials and Methods
### Design of the Seedling-Taking Device  
The seedling-taking and dropping device operates by extracting seedlings and launching entire rows of them. Accurate positioning of the seedling claws is essential during this process. To accommodate the overall structural dimensions of the device, a variable distance mechanism was designed and customized to adjust the relative positions of the seedling claws in real time. The variable pitch slide table is motor-driven, allowing the active camshaft to rotate both forward and backward. As illustrated in Figure 1 (5) below,  
Figure 1: Overall structure diagram: 1. Rack; 2. Seedling-taking mechanism; 3. Seedling delivery mechanism; 4. Seedling cup mechanism; 5. Variable pitch slide; 6. Roller setting device; 7. Topping mechanism; 8. Slide block slide rail; 9. Electric rotary table; 10. Electric push rod motor; 11. Diagram of electrical components. a sliding rod is installed within the camshaft's guide groove, connecting to each slide block. Driven by the right servo motor, the sliding rod moves within the guide groove, driving the slider, which in turn performs linear motion along the guide rail to facilitate changes in the distance between the slide blocks. The spacing can be categorized into two forms: synchronous equidistant spacing and synchronous unequal spacing. For this study, the synchronous equidistant spacing form was selected. The variable pitch slide table employs an intermediate positioning synchronous equal distance variable distance method, enabling high-speed, arbitrary point variable distance operations of multiple slide blocks within the variable range established by multi-station setups. Precise positioning of the slider is achieved through the collaboration of a photoelectric switch installed in the module and an internal induction wheel. To align with the spacing between seedlings as designed in this study, when the custom-made variable-pitch slide block contracts to the midpoint, the center distance between adjacent slide blocks is 42 mm, which corresponds with the center distance of adjacent plug grids. Conversely, when the slide blocks extend to the endpoint, the center distance between adjacent slide blocks is 80 mm, matching the center distance of adjacent seedling cups. The contraction and expansion of the slide block on the variable-pitch slide table drive the air claw connected to the slide block, enabling variable pitch adjustments to accommodate the varying working distances of different workstations, and the sliding table pitch variation is realized by the sliding table active camshaft driven by the motor, as shown in Figure 2a. In this paper, the variable pitch slide module customized by Sid Automation Technology Co., Ltd. (Dongguan, China) is used as the variable pitch mechanism of the claw, and the model of China Jili Pneumatic Equipment Co., Ltd. (Dongguan, China) is BMC-20006 straight-through pneumatic flexible gripper is used as the clamping device. The seedling extraction device primarily relies on the clamping action of pneumatic seedling extraction claws to remove plug seedlings from the plug tray and transfer them to the seedling cup. However, the overall structure of the device introduces both horizontal and angular displacements. The horizontal displacement is primarily facilitated by two electric push rods, while the angular displacement is managed by electric rotary table servo motors located on both the left and right sides, as illustrated in Figure 1 (7). The electric push rod is LTW065-S400-B04-T10-BM2-C121 made by Litway Automation Technology Co., Ltd. (Wuxi, China), which meets the necessary stroke requirements. This electric push rod motor is equipped with an MC2H-M080775F high-inertia servo motor produced by  
Figure 2: Key component structure drawing: (**a**) Variable pitch sliding table active camshaft. (**b**) Fluent bar structure and installation position. (**c**) Electromagnetic actuator installation and dimensional drawing. (**d**) Air claw connection and installation dimensions.