基于运动学目标函数的插秧机分插机构参数优化

Parameters optimization of separating-planting mechanism in transplanter based on kinematics objective function

分插机构优化属于多目标、多参数优化问题。该文为了简化与加快参数优化的过程,提高分插机构的优化效率,在原来"试凑法"的基础上,提出了基于现代目标函数的参数优化方法,即在数学建模的基础上,对分插机构的运动学约束条件进行数字化设计与分析,建立了11个运动学目标函数,求解出目标函数的取值范围分别为:Y1<-2 mm,Y2<90 mm,|Y3|<4 mm,40 mm<Y4<80 mm,55°<Y5<60°,Y6>260 mm,Y7<30 mm,-10°<Y8<20°,65°<Y9<80°,Y10>2.5,Y11>20 mm。在分插机构辅助分析设计平台中,给定初始参数:椭圆齿轮长半轴a=16.65 mm,椭圆短轴与长轴之比k=0.98,栽植臂相对行星架初始安装角α0=-100°,行星架的初始安装角φ0=24°,行星架拐角δ0=7°,秧针尖点与行星轮转动中心的距离S=176 mm,株距H=150 mm,中心轴的角速度W=200 rad/s。利用目标函数的取值要求进行机构参数优化,得到了满足插秧要求的机构参数:a=22.65 mm,k=0.987,α0=-52°,φ0=27°,δ0=16°,S=181 mm,H=130 mm,W=200 rad/s。经比较分析验证本方法可有效提高分插机构参数优化精度与效率,对其他农业机械参数优化问题具有一定的借鉴意义。

Transplanting mechanism optimization is a strong coupling, fuzziness, and nonlinearity optimization problem which involves multi-objectives and multi-parameters. The optimization results are pareto. For these feasible solutions, how to look for the best optimization result is the key issue to improving the transplanting mechanism optimization design. At present, only some agricultural experts can identify which one is the best through the motion trajectory shape. However, sometimes this only has subtle differences between some results, and the experts cannot judge which one is more optimal. There are eleven optimization goals for the transplanting mechanism on the high-speed-type rice transplanter. They are as follows： 1） When the transplanting mechanism is operating, the two transplanting arms cannot be crashed by each other; 2 If the transplanting arm is fetching the seedlings, the supporting part of the seedling needle cannot crash into the seedling gate; 3） The fetched seedling block is oblong and the trace of fetching seedlings at the seedling box is vertical; 4） The transplanting arms shaft should not contact with the lower part of the transplanted seedlings; 5） The angular difference between the angle of pushing the seedling and that of fetching the seedling should remain between 55~ and 60~; 6） The distance between the seedling-separating needle tip and the seedling-pushing needle tip was more than 260mm; 7） The length of the ground socket, along the direction of transplanter travel, formed by the absolute motion trajectory, must be less than 30 mm; 8） To ensure the uprightness of the seedlings after transplanting, the included angle between the seedling needle and horizontal line should remain between -10~ and 20~ when fetching the seedlings; 9 The included angle between the seedling needle and horizontal should remain between 65~ and 85~ when the pushing of the seedlings is beginning; 10） The gear modulus is more than 2.5mm; 11 ） The distance is more than 20 mm between the bottom of the disk and the ground. The importance of all target sequence of numbers is based on the above objectives. In the above objectives, the first two goals are the movement interference judgment of the transplanter, and can obtain accurate decision results, and the rest of the nine goals have a certain fuzziness, namely： the target decomposition to each goal function value is not the only value, but a range, and the values of the range all can satisfy the kinematic movement requirement. Therefore, based on the modem design optimization method and mathematical modeling, this article was mainly for digital design and analysis of the kinematics constraints of the transplanting mechanism, According to the working principle of the transplanting mechanism, combined with high-speed photography and the results of field work requirements, it established eleven kinematics objective functions. According to each objective function parameters and the trajectory of the transplanting mechanism required, researchers obtained all the ranges of the eleven objective functions. The functions were then applied to the aided analysis and design optimization platform, and objective functions parameter optimization design requirements for institutions were combined, to simplify the process of transplanting mechanism parameter optimization to improve transplanting mechanism parameter optimization efficiency purposes. In this paper, other agricultural machinery parameter optimization problem had a certain significance.