基于节曲线凸性判别的行星轮系移栽机构解析

为了建立非圆齿轮凸性与理想移栽轨迹之间的直接联系,使行星轮系移栽机构更好地满足作业要求,提出一种基于非圆齿轮节曲线凸性指标的不等速行星轮系机构参数求解方法。根据给定的运动轨迹,建立全局坐标系;将轮系简化为二杆二自由度开链机构（2R机构）,建立基于移栽轨迹的机构运动求解模型,提出非圆齿轮节曲线凸性判定指标,确立轮系中心位置变化范围即解析区域。根据运动学原理,由二杆二自由度开链机构复演理想移栽轨迹,求解轮系传动比,建立不等速传动比计算与分配模型,得到杆长、杆长比、轮系传动比、非圆齿轮节曲线凸性值等移栽机构参数,建立可以形成给定移栽轨迹的移栽机构参数信息图。避免了调试非圆齿轮节曲线的盲目性、优化机构尺寸和结构设计中双臂干涉等问题,为设计可形成特定轨迹的轮系机构提供参考。对几种常见移栽轨迹进行计算分析,以“鹰嘴形”水稻钵苗移栽轨迹为例进行非圆齿轮行星轮系钵苗移栽机构的设计仿真与样机试验,仿真轨迹、试验轨迹与给定理想轨迹基本一致,验证了计算模型的正确性与设计机构的可行性。

Solution and Analysis of Transplanting Mechanism with Planetary Gear Train Based on Convexity of Pitch Curve

With the goal of improving the performance of planetary gear train transplanting mechanism, the direct connection between convexity of pitch curve and the ideal transplanting trajectory was established. A method was proposed to abstract the parameters of a planetary gear train with noncircular gears based on the convexity of non-circular gear pitch curve index. Firstly, a global reference coordinate system was established based on the transplanting trajectory;next, the planetary gear train was simplified to a two-link, two degrees of freedom, and open loop chain mechanism with two revolute joints (a 2R mechanism), and a mechanism motion solving model was established based on ideal transplanting trajectory. According to the conversion relation between transmission ratio curve and non-circular gear pitch curve, the non-circular gear pitch curve convexity judgment index was put forward. The range of the transplanting mechanism with planetary gear train central position, namely the analytic domain was established. According to the kinematics principle, the ideal transplanting trajectory was replayed by a two-link, two degrees of freedom and open loop chain mechanism. The transmission ratio of gear train was calculated, and the calculation and distribution model of transmission ratio was established. The parameters of transplanting mechanism were calculated, such as the length of links, length ratio of link, and non-circular gear pitch curve convexity judgment index. The parameter information diagram of transplanting mechanism with a given transplanting trajectory was drawn. According to the requirements of transplanting agronomy, the engineering practical solution was preferred in the information map. And the blindness of adjusting non-circular gear pitch curve was avoided. The method was used to calculate and analyze several common transplanting trajectories. The eagle-nosed transplanting trajectories were chosen to design the transplanting mechanism with planetary gear train. Simulation analysis showed that the simulation trajectory and the test trajectory were basically the same as the given ideal trajectory. The correctness of the calculation model and the feasibility of the design mechanism were verified.