Design and optimization of transplanting mechanism with B-spline non-circular planet gear train for rice pot seedling

Abstract: The pot seedling transplanting has the advantages of non-hurting root and no need of recovering period, so it can extend the crop growing period, increase and bring forward the effective tillering, which is very important to the food security. Since Japan invented the first transplanter for rice pot seedling in 1975, large agricultural machinery companies have producted their own models in succession, such as Yanmar, Iseki and so on. The materials and manufacture technologies have been improved through the forty years development, but the basic structure and working principle are still the same. All the transplanting machines use 3 sets of mechanism to complete 3 kinds of movements of picking, transporting and planting. The existing machines have the disadvantages of complex structure, high cost and low efficiency. In domestic, the rice pot seedling transplanting machine uses double cranks to complete the 3 kinds of movements, it has relatively simple mechanism, and is suitable for the rice pot seedlings transplanting, but the problems of severe vibration and low efficiency are still existent. According to the above problems, the paper adopted the cubic non-uniform rational B-spline curve theory to fit non-circular gear pitch curve with coincidence of first and last data points as a closed curve. The shape of non-circular gear pitch curve was controlled and expressed through selecting the 13 data points, a new rotary planet gear train mechanism with non-circular gear was developed for rice pot seedling transplants. Through the kinematic analysis of the mechanism, the attitude and sharp point trajectory objective functions of seedling clip were built and transformed into the optimization mathematics model based on optimization of target determined. A computer aided analysis and optimization software of the transplanting mechanism with non-circular planet gear train for rice pot seedling was developed on the MATLAB GUI platform. Through adjusting data points by the man-machine interaction, the attitude and sharp point trajectory of seedling clip were optimized, and a set of structural parameters were obtained to meet the requirements of the rice pot seedling transplants. A three dimensional model was built in software of UG 8.0, and input to software of Admas 2010. The simulation results show that, both track results of theoretical analysis and virtual prototype experiment are fundamentally consistent, so the correctness of the kinematics mathematical model was verified by the virtual experiment. The research can provide a theoretical basis for developing transplanting mechanisms for rice pot seedling.