Research on design method of non-circular planetary gear train transplanting mechanism based on precise poses and trajectory optimization

Among all kinds of transplanting mechanisms which are the important parts of transplanters, the planetary gear train transplanting mechanism is widely used for its excellent transmission performance, but it is difficult to design the gear pitch curves and structural parameters according to the trajectory and pose requirements of transplanting. The current design method of the non-circular planetary gear train transplanting mechanism cannot ensure the precise position and posture in the crucial points of transplanting trajectory, nor take both the anticipated trajectory and the smoothness of the gear pitch curves into account, it will only get one solution which is available for mechanism design. In order to solve those problems, the non-circular planetary gear train transplanting mechanism is analyzed as a combination of the bar-group and gear train system. According to the transplanting requirements, three points with precise position and posture which called pose points in the trajectory are given to obtain the solution domain of the parameters of bar-group, and then trajectory shape control points are inlet to design the desired shape of the transplanting trajectory and obtain the transmission ratio curve which can be used to get the gear pitch curve. The most suitable parameters of bar-group in solution domain are selected based on the smoothness of the gear pitch curves. This article establishes three-dimensional model of the mechanism and utilizes the ADAMS to carry out a motion simulation; all simulation results are consistent with theoretical design results, which confirm that the design method based on prescribed pose points and trajectory control points is adequate for the transplanting mechanism. With the proposed method, the selectivity of the mechanism’s parameters solution is increased, and transmission performance benefits from the integrated design of trajectory control and the smoothness of the pitch curves.