鸭嘴开合控制机构张角误差分析

Analysis and Optimization of the Duckbill Opening Angle Error of the Transplanting Mechanism

针对鸭嘴开合控制机构中高副关节长时间磨损导致高副关节产生微小间隙,与高副关节产生的微小位移相互抵消,致使栽植鸭嘴开合角度变小、栽植鸭嘴的钵苗无法落入植苗穴孔、造成漏栽的问题,通过将高副关节产生的微小位移融入低副关节尺寸,消除鸭嘴开合控制机构产生的微小位移对鸭嘴开合角度的影响。为此,分析了鸭嘴开合控制机构原理与影响微小位移的参数,建立了高副关节微小位移数学模型,优化了杆件参数,使微小位移最小;确定微小位移融入关节与融入量,得出融入后的机构原理模型;基于误差传递矩阵法分析栽植机构末端鸭嘴张角误差,微小位移融入低副关节尺寸后,鸭嘴张角误差很小,仅为0.035°,对鸭嘴机构的开合影响几乎不存在。结果表明:将高副关节微小位移融入低副关节尺寸的方法,可以有效减小执行机构末端的位置误差,为移栽机鸭嘴开合控制机构的优化设计提供新的方法,为机构高低副关节的合理分配提供一种新的思路。

a method of transferring the tiny displacement of a higher pair joint into the size of a prismatic pair joint was proposed to weaken this influence of the tiny displacement of a higher pair joint on the transplanting duckbill opening angle.This influence of abrasion and higher pair joints resulting from that abrasion clearance of a higher pair joint offset the tiny displacement of a higher pair joint,caused that the planting duckbill angle opening became smaller or forever closed,leading to the failure of transplanting seedlings.For overcoming the existing problem above,firstly,the tiny displacement mathematical models of higher pair joints were established through analysis of both existing planting duckbill mechanical principle and parameters impacting on the tiny displacement size,such as length of bars and angle between a bar and an adjoining one.And these parameters of the bars were optimized by MATLAB software to make the tiny displacements trend to zero.Besides,relationships and equations of length of bars and angle between two bars were obtained from the mathematics models when the higher pair joint tiny displacement was smallest,as well as relationships between bar ＇s length and angle were all lineal,besides the tiny displacement values were acquired by these equations.Subsequently,the principle of transferring the tiny displacement of a higher pair joint into the size of a prismatic pair joint was referred from the planting duckbill mechanism properties analyzed to make the precision of transplanter duckbill opening angle higher,including the work performance,the dynamic characteristics,mechanical error,and mechanical vibration.Meanwhile,a prismatic pair joint should be chosen as the joint that the tiny displacement was transferred into,because a rotational joint was made to move along the radial direction,a rotational joint position would be changed,however,a prismatic pair joint was made to move along the vertical direction,its horizontal motion would not be changed.Then a method of transferring the tiny displacement of a higher pair joint into the size of a prismatic pair joint was learned from the motional relationship among mechanism components.Furthermore,a transplanting duckbill mechanism improved by exchanging the positions of the higher pair joint and the lower pair joint was obtained,which made the opening angle of the planting duckbill opening angle more accurate,besides the new transplanting duckbill mechanical degree of freedom is one.It showed that the movement of the transplanting duckbill mechanism improved is uniquely determined,that this idea is completely true and that success rate of transplanting seedings was evidently increasing.In order to analyze the opening angle error of the transplanting duckbill mechanism improved,local coordinate systems of transplanting duck bill mechanism improved were established,and the transferring error matrix of the mechanical positions was used for calculating the angle error value of the transplanting duckbill mechanism improved,and calculation result showed that its error value was only 0.035°.It is so tiny that the transplanting duckbill mechanism improved can completely satisfy its working performance.The method of transferring the tiny displacement of a higher pair joint into the size of a prismatic pair joint is completely feasible to improve the work performance of the transplanting duckbill mechanism and make the working accuracy of the transplanting duckbill mechanism keep stable for long time.Meanwhile,transferring the tiny displacement of a higher pair joint into the size of a prismatic pair can provide a new way for designers to optimize the work performance of mechanisms that were not able to keep stable when they were working.This method can offer a new way to place higher pair joints and lower pair joints reasonable at mechanisms.