Optimal Design and Experiment Research of Planetary Gear Train with Two-order Non-circular Gears Seedling Pick-up Mechanism on Seedling Transplanter
|School||Zhejiang University of Technology|
|Course||Mechanical Design and Theory|
|Keywords||Seedling Transplanter Seedling Pick-up Mechanism Non-circular Gears OptimalDesign Planetary Gear Train|
Seedling pick up mechanism is the key factor of promoting the development oftransplanting macine from semi-automatic to fully automatic, is the current hot topics in theresearch of agricultural machinery. Traditional seeding pick up mechanism mainly include thesliding-block linkage combined mechanism and non-circular gear planetary intermittent system,performance due to any agency selection needs to be improved. Based on working characteristicsof the traditional seeding pick up mechanism, and combined with non-uniform transmission ofnon-circular gear research achievements. The seeding pick up mechanism of complete rotarynon-circular gear planetary system are put forward, targeting Olecranon-shaped Trajectory.Through the analysis of the trajectory of planetary system, it is found out that using cubicnon-uniform B-spline curve to fitting function of non-circular gear transmission ratio directly,and realized the periodic quadratic unequal amplitude swinging motion of seeding pick up arm,this is the Olecranon-shaped Trajectory needed. On this basis, we carry out the agency’skinematic optimization, dynamic characteristics analysis and experimental verification. At last,the design and physical prototype and carry out the take seedlings related experimental researchin seedling experiment platform. Paper main research work is as follows:1）In this paper, The seeding pick up mechanism of rotary non-circular gear planetarysystem and the Olecranon-shaped Trajectory was proposed, and found that the cycle of theperiodic quadratic unequal amplitude swinging motion of seeding pick up arm is the cause of theOlecranon-shaped Trajectory formed, by analysis the formation mechanism of theOlecranon-shaped Trajectory.2）Kinematics modeling and parameter optimization: First of all, The fitting of freedomsecond order non-circular gear and a mathematic model of the secondary non-circular gear isestablished, by using13data points for the transmission ratio. The second, the influence of thetransmission ratio parameters and trajectory parameters upon the ring size of Olecranon-shapedTrajectory, location and path form were studied, which is necessary for get the ideal trajectoryfor institution parameter constraint. Third, the seeding pick up mechanism of work target will beset to ten, mathematical model is set up, and quantify the ideal interval of each target. In the end,optimization design software for the seeding pick up mechanism of free second-ordernon-circular gear, developed based on the parameters of the direct optimization method, is usedto optimize many of related parameter, the transmission ratio parameter as follows:[（0，0.6999），（25，0.7777），（35，0.9721），（80，1.7887），（105，1.1666），（160，0.6844），（210，0.8166），（230，1.0499），（256，1.2443），（288，1.1277），（300，0.9955），（335，0.7310），（360，0.6999）], The structural parameters as:[68mm，139°，-84°，30°，215mm],The ten of kinematics target value as:（5.74，2.5,139.226，20.18,4.38,26,108.41,2.67,313,25）.3）Structural design and dynamics analysis of the organization: By establishing the virtualprototype, the interference of the mechanism is checked, and cam is verified the correctinstallation position that ensure the orderly implementation of grip action. Dynamics model was established and the analysis of features of each component on the force, it’s found that for theseeding pick up mechanism of free second-order non-circular gear, significant increase in thebearing reaction force of center shaft when the planet speed greater than100r/min. So the planetspeed should be lower than100r/min.4）Experiment research: Researching on the physical properties of pot seeding, we set theinitial distance between two seeding claws as20mm by counting the positions of the seedlings inthe pot; And confirm the minimum amount of seeding claw clamping as10mm by practicing thetest on coefficient of friction between seedling claw and the pot, compressive strength test of potand the strength of seed-picking up. We practice test on the central axis bearing force ofseed-picking up, and the consequence shows that when the mechanism revolving speed is below80r/min, Mechanics characteristic is smooth and theoretical analysis of bearing force arebasically identical, which verified the correctness of the theoretical analysis model. The theoryand test results show that free second-order non-circular gear planetary gear train seed-pickingup mechanism can realize as higher seed-picking up efficiency as160p/min. Take seeding trayobliquity, clamping and the depth of seed-picking up as factors, and set three levels in everyfactor. Carrying out all factors experiment when the revolving speed is below60r/min, theoptimal combination is confirmed: seed-picking up intersection angle is90o,clamping is15mm,the depth of seed-picking up is35mm and the highest success rate of seed-picking up is94%;Carrying out L43(3) orthogonality experiment when the revolving speed is below80r/min, theoptimal combination is confirmed: seed-picking up intersection angle is100o,clamping is12mm,the depth of seed-picking up is35mm and the highest success rate of seed-picking up is90%.Carrying out the test on pot seedling movement rule in the period of falling, pot seedlingmovement rule is fit with the theoretical design in the pushing. After pot seeding deviating fromseeding claw, pot seeding moves downward and forward, it is the ideal handover state of potseeding. However, the forward speed of pot seeding is faster when the revolving speed is below80r/min, which goes against handover. To ensure the pot seeding moves forward and downwardwith a higher revolving speed, we must enhance the seed-pushing points, and increase thedownward speed of seeding deviating from seeding claw.