基于近似多位姿的轮系式钵苗移栽机构运动综合

作业轨迹形状和在特定位置移栽臂的姿态要求是移栽机构设计过程需要考虑的首要问题。为了能获得多个期望位姿且兼顾一定形状的作业轨迹,提出一种基于近似多位姿的非圆齿轮行星轮系移栽机构设计方法。基于运动学映射理论将8个期望位姿点的信息矩阵通过四元数转换至三维空间,在对该矩阵进行奇异值分解后,通过引入特征向量扩大一般解空间。结合约束条件求解得到3组RR型二杆组,根据移栽机构的工作范围选取其中两组合适的二杆组构成四杆机构,且该机构连杆上的一点可依次近似通过所有设定的位姿点形成一条完整的“8字”型轨迹。根据其中一组二杆组的运动特点求解非圆齿轮的传动比,以非圆齿轮节曲线圆度性为目标,以封闭轨迹上的部分形状可调节段拟合点位置为变量（即不改变关键轨迹段上型值点的位姿）,利用遗传算法优化得到一组具有较好圆度性的非圆齿轮节曲线。最后进行了水稻钵苗移栽机构的设计与试验,理论与试验的移栽姿态和轨迹形状具有一致性,且取苗试验的成功率达到设计要求,有效地验证了运动综合和设计方法的正确性。本研究可为具有多位姿要求的新型移栽机构的设计提供方法借鉴。

Motion Synthesis of Rotary Pot Seedling Transplanting Mechanism Based on Approximate Multi-pose

The shape of the work trajectory and the pose requirements of the transplanting arm in a specific position are the primary problems to be considered in the design process of the transplanting mechanism. A non circular gear planetary gear train transplanting mechanism based on approximate multi pose was presented in order to obtain multiple desired positions and take into account the specific shape of the work trajectory. The information matrices of eight expected poses were transformed into three dimensional space by quaternion using kinematics mapping theory, and the general solution space was expanded by introducing eigenvectors after the singular value decomposition of the matrix. A four bar mechanism was formed by selecting two sets of suitable two bar groups, whose coupler trajectory can approximately go through all the prescribed poses. The transmission ratio of non circular gear was solved based on the kinematic characteristics of the selected two bar group. Moreover, after establishing the circurity function and determining the design parameters, the shape of the non circular gears was optimized by using the genetic algorithm. Finally, the prototype of the transplanting mechanism was manufactured for the primary test. A testing result that had an identical shape and operating poses with that of theoretical calculation was obtained, as well as the qualified picking success rate, which effectively verified the correctness of the motion synthesis and design method. This method can be used for reference in the design of transplanting mechanism with multi pose requirement.