Trajectory matrix-guided optimal design of non-circular gear train seedling throwing mechanism for rice pot seedlings

Rice transplanting by hand offers advantages such as minimal plant injury and a short recovery period. The key to mechanizing this process lies in replicating the ideal final trajectory of hand-transplanting through mechanical equipment. Based on the motion characteristics of manual transplanting, this study divides the transplanting process into three stages: seedling pickup, seedling transport, and seedling placement. Using the trajectory and posture of the human hand as a reference, an ideal mechanized transplanting trajectory was planned. Manual transplanting was simplified into a 2R open-chain mechanism configuration. A non-circular gear mechanism was employed to constrain the 2R open-chain mechanism to two degrees of freedom, proposing a non-circular gear transplanting mechanism design. Based on normalization principles, the ideal transplanting trajectory and the training trajectory corresponding to the feasible solution domain were normalized and feature-coded. The end-effector trajectory was then represented using a trajectory matrix. By constructing an objective function, a globally optimal mechanism solution was obtained through optimization across the entire solution domain. A test bench for the transplanting machine was developed. High-speed camera analysis of the transplanting mechanism’s working trajectory demonstrated that the optimal mechanism solution reproduces the ideal mechanized transplanting trajectory, meeting the operational requirements for mechanized transplanting.