## 1 Introduction  
Tomatoes are one of the most popular and important vegetables in the world. According to the World Food and Agriculture Organization (FAO) 2019 statistics, the world tomato-planting area was 5,030,000 hectares, the harvested volume being approximately 180,766,000 tons. Moreover, the harvest area and volume are increasing year-on-year [1]. The use of rootstock varieties -- with their excellent root vigor which absorb water and nutrients effectively -- can be used to reduce the quantity of chemical fertilizers, reduce the frequency of pesticide application, increase crop yields, reduce environmental pollution [2; 3; 4; 5], and reduce various abiotic and biotic stresses under intensive cultivation [6; 7]. The most serious problems associated with tomato planting are those of soil-borne diseases and insect pests. Before the popularization of grafting technology, chemical disinfectants --such as methyl bromide--were generally used to eliminate diseases and insect pests. Although the impact of these substances is remarkable, it can have serious environmental ramifications. Consequently, environmental protection legislation has banned such practices in many countries [8; 9], and grafting has become prevalent in the production of tomato seedlings. Compared with natural screening, breeding, or species hybridization, grafting technology is a fast and effective method to obtain the desired crop characteristics to solve current cultivation dilemmas [10]. The rootstocks of grafted tomato seedlings used at different latitudes can differ considerably. In particular, verticillium wilt, wilt disease, root nodule nematode, and white silk-worm disease can be overcome in temperate regions by grafting appropriate tomato root stock varieties (such as Maxifort). In subtropical and tropical regions, bacterial wilt and waterlogging problems can affect tomato production, and eggplant rootstock varieties\(-\)such as EG203, which is resistant to bacterial wilt and waterlogging\(-\)can be used for the grafting process [11]. Consequently, grafted tomato seedlings in temperate regions are mainly tomato-tomato grafted seedlings, while those in subtropical and tropical regions are mainly tomato-eggplant grafted seedlings. In short, the development of cultivation strategies that suit local conditions, based on climatic differences and industrial management models, is essential. The traditional grafting operation is a manual process, a task that requires attention, skill, and training. After accumulated experience, the yield rate of grafted seedlings can be maintained at an acceptable level. In Taiwan, professional grafters can produce 180-200 grafted seedlings per hour, with a survival rate of 80-90% [12]. Moreover, there is a seasonal demand for grafted tomato seedlings, with July-September being the peak season. Based on a survey by the Agriculture Committee of the Executive Yuan, the agricultural employment population in Taiwan in 2021 only accounted for 4.7% of the total employment population. Among those engaged in agriculture, 64% are over 50 years old, and 20% are over 65 years old. The agricultural industry faces the dilemma of an aging population in rural areas, a lack of labor, and difficulties in training professional operators, resulting in existing operators having to work intensively, for long periods of time. Consequently, the use of machinery for grafting operations has become a growing trend, as it can solve the problem of labor shortages, reduce production costs, and improve the work environment [13]. The three most important tasks required of grafting machines include the clamping and positioning of seedlings, beveling, and grafting. However, current grafting methods in Taiwan make the mechanization of grafting very difficult, as the country is accustomed to using tomato scion to graft the eggplant root stock. The appearance and size of the two differ, making the grafting process difficult.