# Design of a Sweet Potato Transplanter Based on a Robot Arm
## 1 Introduction  
The sweet potato is an important food for countries all over the world. It provides raw starch for industrial uses, and it is a high-quality, anti-cancer, and energy-providing health food [1, 2, 3, 4, 5]. With the reduction in the number of agricultural workers, transplanting machinery will inevitably become the main development direction of agricultural mechanization [6, 7, 8]. It is difficult to separate sweet potato seedlings from each other for planting, due to their interweaving branches and the significant differences in morphology [9, 10, 11, 12]. Therefore, semi-automatic transplanting machinery has been adopted worldwide [13, 14, 15]. For example, the semi-automatic chain clip-type sweet potato seedling transplanter produced by the American Marcinick Company can complete more than ten plantings at one time, but it damages the soil structure and is mainly used for direct insertion operations [16]. [PERSON] et al. [17] developed the 2 ZGF-2 duplex sweet potato transplanter, which can accomplish the oblique transplanting of sweet potatoes and transplant two rows of sweet potatoes at one time. In recent years, a connecting rod-type sweet potato transplanting machine has been favored by scholars. The Japanese company Dongfeng Well Seki has produced a self-propelled sweet potato transplanting machine, using four connecting rod mechanisms to achieve the sweet potato transplanting. The sweet potato transplanting height can be adjusted by adjusting the installation position of the connecting rod, and the main operation method is oblique planting. [PERSON] et al. [18] designed a clip type sweet potato naked seedlingtransplanting machine. The reference track of the sweet potato transplanting was defined, and the dimensions of each connecting rod were obtained through mathematical modeling and virtual prototype analysis to accomplish oblique transplanting. [PERSON] et al. [19] and [PERSON] et al. [20] designed a sweet potato ship-type transplanting mechanism through simulation analysis. However, no prototype was manufactured for field tests. It can be seen that at the present stage, a sweet potato transplanting machine can only achieve direct planting or oblique planting, and a sweet potato transplanting machine can only achieve one type of transplanting method. The different planting terrains typical of sweet potato fields require different transplanting methods, and different transplanting methods have a significant impact on the survival rate and yield of sweet potatoes. The shortage of sweet potato mechanized transplanting methods will restrict the yield and production efficiency of sweet potatoes. Designing a transplanter that can realize a variety of transplanting methods is a good solution to solve this type of problem. A mechanical arm is compact in structure and can execute complex moving trajectories. Therefore, many scholars have researched the use of mechanical arms for use in transplanting machinery. [PERSON], [PERSON] et al. [21] developed a PLC-controlled multi-tasking robot transplanting cell for greenhouse seedlings. [PERSON], [PERSON] et al. [22] designed a reciprocating transplanting mechanism that uses linear motors and cylinders, as well as an end-effector that can efficiently pick and plant seedlings at a given position. However, there is no corresponding special transplanting robot arm for crops like sweet potato seedlings, which have significant requirements for transplanting trajectories. Replenishing seedlings has always been a challenge for transplanting machinery, and the difficulty lies in how to detect missing seedlings. Due to the rapid development of machine vision in recent years, seedling replanting mechanisms based on visual inspection have gradually emerged. [PERSON] et al. [23] used machine vision to detect the health of cavity seedlings and control the end-effector to grasp the potted seedlings for replenishment operations based on a greedy genetic algorithm.