【目的】针对单行星架轮系式钵苗移栽机构存在的取植苗动作难以兼顾而影响移栽质量的问题，提出一种与传统移栽机构旋转方式相反且输入、输出不等周期的分段式变传动比轮系机构。【方法】首先，构建了不完全齿轮组连续啮合角度条件方程，求解分段式不完全齿轮组实现连续啮合所需运动参数；而后，将非圆齿轮的不等速传动比和分段不完全齿轮的三次高幅值波动传动比组合，获得钵苗移栽机构实现环扣轨迹所需的多次不等幅传动比，并建立含不完全齿轮组的非圆齿轮行星轮系移栽机构运动学模型，编写了基于Matlab的移栽机构辅助设计程序；同时，结合水稻钵苗移栽农艺要求，通过人机交互方式优选得到了一组可实现大位移慢取秧(取苗环扣47mm)、大植苗角(植苗角度80.6°)的环扣状钵苗移栽轨迹的机构参数。【结果】最后，对机构的仿真结果和理论计算数据进行对比分析，结果表明不完全齿轮组各项参数满足要求，且机构的运动轨迹及姿态与理论基本一致。【结论】通过样机试验，测量得到的取苗角为20.95°，植苗角度为80.3°，验证了组合式变传动比移栽机构设计的可行性。

【Objective】To address the problem in single-planetary-wheelset transplanter mechanisms where the seedling picking and placing motions cannot be simultaneously optimized—thereby degrading transplanting quality—we propose a segmented variable gear-ratio wheelset mechanism whose rotation direction is opposite to that of conventional transplanting mechanisms and whose input and output periods are unequal. 【Method】First, we derived the continuous meshing angular condition equation for a segmented incomplete-gear set and solved for the motion parameters required for the segmented incomplete gear set to achieve continuous meshing. Next, by combining the non-uniform transmission ratio of an oval (non-circular) gear with the cubic high-amplitude fluctuation transmission ratio of the segmented incomplete gear, we obtained the multi-step unequal-amplitude transmission ratios required for the ring-loop (ankle-shaped) seedling-transplanting trajectory. We then established a kinematic model of a non-circular gear planetary wheelset transplanting mechanism that includes incomplete gear sets and developed a MATLAB-based auxiliary design program for the transplanter. At the same time, in accordance with rice seedling transplanting agronomic requirements and using a human-machine interactive selection process, we selected a set of mechanism parameters that realize a ring-loop transplanting trajectory capable of large pick displacement with slow picking (pick loop 47 mm) and a large planting angle (planting angle 80.6°). 【Result】Finally, we compared simulation results with theoretical calculations. The results show that the parameters of the incomplete gear set meet the requirements, and that the mechanism’s motion trajectory and posture are in substantial agreement with theory. 【Conclusion】Prototype tests measured a picking angle of 20.95° and a planting angle of 80.3°, validating the feasibility of the combined-variable transmission-ratio transplanting mechanism design.