Design of Vegetable Pot Seedling Pick-up Mechanism with Planetary Gear Train

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Chinese Journal of Mechanical Engineering Open Access

ORIGINAL ARTICLE

Design of Vegetable Pot Seedling Pick‑up Mechanism with Planetary Gear Train Zhipeng Tong1,2, Gaohong Yu1,2*, Xiong Zhao1,2, Pengfei Liu1,2 and Bingliang Ye1,2

Abstract  It has been challenging to design seedling pick-up mechanism based on given key points and trajectories, because it involves dimensional synthesis and rod length optimization. In this paper, the dimensional synthesis of seedling pickup mechanism with planetary gear train was studied based on the data of given key points and the trajectory of the endpoint of seedling pick-up mechanism. Given the positions and orientations requirements of the five key points, the study first conducted a dimensional synthesis of the linkage size and center of rotation. The next steps were to select a reasonable solution and optimize the data values based on the ideal seedling trajectory. The link motion was driven by the planetary gear train of the two-stage gear. Four pitch curves of noncircular gears were obtained by calculating and distributing the transmission ratio according to the data. For the pitch curve with two convex points, the tooth profile design method of incomplete noncircular gear was applied. The seedling pick-up mechanism was tested by a virtual prototype and a physical prototype designed with the obtained parameter values. The results were consistent with the theoretical design requirements, confirming that the mechanism meets the expected requirements for picking seedlings up. This paper presents a new design method of vegetable pot seedling pick-up mechanism for an automatic vegetable transplanter. Keywords:  Combined incomplete noncircular gear, Mechanism dimension synthesis, Planetary gear train, Seedling pick-up mechanism 1 Introduction Seedling transplantation is an important part of vegetable production: over 60% of vegetable varieties adopt a seedling cultivation method [1]. Generally, mechanical transplantation is more efficient and practical than artificial transplantation. The core of an automatic vegetable transplanter are the seedling pick-up mechanism and the seedling planting mechanism. The automatic machine improves the work efficiency and reduces the leakage rate relative to the case of a semiautomatic machine which comprises only a seedling planting mechanism. The seedling pick-up mechanism is the bottleneck in automatic transplanter development.

*Correspondence: [email protected] 1 Zhejiang Province Key Laboratory of Transplanting Equipment and Technology, Zhejiang Sci-Tech University, Hangzhou 310018, China Full list of author information is available at the end of the article

Robotic seedling pick-up mechanism is widely used and highly practical. It simulates the manual activity of collecting vegetable pot seedlings from a bowl and pushing them into the seedling planting mechanism. Common ways of seedling pick-up are pneumatic mechanism [2], multilink mechanism [3–6], push-out and clamping combined mechanism [7], and their mixed forms. An automatic vegetab