计及铰链间隙的弹射式移栽机构非线性动力学特性分析

Non-linear dynamic characteristics of ejection transplanting mechanism with joint clearance

旋转式移栽机是当前的研究热点,该类移栽机结构简单、安全可靠,且能同时完成取苗,运苗和栽植的工作。然而目前的研究主要为功能设计,未考虑由于加工误差、设计精度等原因导致的铰链间隙问题。间隙会引起副元素之间的碰撞和振动,使得系统的约束条件,自由度数目和拓扑结构发生变化。因此,在研究移栽机构的动力学特性时,有必要考虑铰链间隙的影响。基于对副元素接触模式的划分,建立了间隙旋转铰接触力求解模型,并用Fortran语言编写了接触力的求解子程序,将其加载到了ADAMS函数求解库中,基于该程序对弹射式移栽机构模型进行了仿真和计算。结果表明,铰链间隙的尺寸不宜过大或过小,否则会导致副元素间剧烈的碰撞和振动。这项工作为提高含间隙移栽机构的控制精度提供了参考。

Rotary transplanting mechanism is a current research hotspot, and it is simple in structure, safe and reliable, and can complete the work of picking, transporting and planting seedlings at the same time. However, current research mainly focuses on function design, the problem of joint clearance caused by machining error, design precision, etc. is not considered. The clearance can cause collision and vibration of pair elements in joint and variation of constraint conditions, number of DOF and topological structure of the system. So, the influence of joint clearance has to be considered when studying dynamic characteristics of a transplanting mechanism. Here, based on dividing contact modes of pair elements, the contact force solving model of a clearance revolute jointwas established. A solving subroutine for contact force was compiled with Fortran language, it was embedded into the function solving library of ADAMS. An ejection transplanting mechanism considering revolute joint clearance was simulated based on this subroutine. Results showed that the joint clearance should not be too large or too small, otherwise it can cause severe collision between pair elements and their vibration;the study results provide a reference for improving control precision of transplanting mechanisms with joint clearance.