【作者】 张瑜；

【导师】 顾寄南；

【作者基本信息】 江苏大学 ， 机械工程， 2017， 硕士

【摘要】 随着自动化生产线在智能制造业中的广泛应用,其整机平稳性对产品生产质量的影响日益显著。推进机(又称送料机)作为自动化生产线的重要组成部分,其运动平稳性直接影响整机性能。本文以某胶囊自动化生产线的推进机为研究对象,综合考虑机构运动学特性与齿轮啮合特性对机构传动性能的影响,以提高机构的运动平稳性为目标,提出将NSGA-Ⅱ遗传算法应用于齿轮连杆机构的多目标优化设计中。同时,探讨了齿廓修形参数对机构运动平稳性的影响。论文主要工作及结论如下:首先,根据推进机的工作要求,采用曲柄齿轮齿条机构作为推进机的主传动机构,在不改变电动机转速的情况下,实现机构的自动换向与长距离输送功能;针对曲柄齿轮齿条机构的设计,在考虑机构运动学特性与齿轮啮合特性的基础上,以齿轮摆角、角加速度和齿轮齿条重合度作为优化目标,建立了机构的多目标优化数学模型;并利用NSGA-Ⅱ遗传算法对该模型进行了多目标优化,得到一个Pareto最优解集,进而确定了一组最优设计方案;基于Matlab仿真软件对优化前后机构的运动学特性进行了分析。结果表明:在保证机构运动平稳的前提下,优化后机构的齿轮摆角由优化前的7.365 rad增至9.875 rad,提高了该机构作长行程往复运动的能力。其次,结合ANSYS有限元技术与ADAMS虚拟样机技术,对优化后的机构进行了刚柔耦合动力学仿真分析;基于有限元接触分析确定了齿轮的最大修形量,并提出了长修形与短修形两种修形方案;然后从动力学与静力学角度出发,分析和探讨了齿轮在不同载荷工况下,两种修形方案对其传动特性的影响。结果表明:本文机构中的齿轮更适合采用短修形方案,其修形长度为1 mm,修形量为0.02 mm,修形后齿轮的啮合冲击得到明显改善,提高了机构的整体平稳性。最后,对齿轮座固有频率、输出轴静力学特性以及推送过程的运动学特性进行了分析,并对比了定速推送、优化前推进机推送和优化后推进机推送时,推爪与模条在初始时刻的接触情况,以此验证推进机结构的合理性。结果表明:优化后的推进机结构能保证安全承载,且具有加速稳定、运动平稳及推送初始时刻瞬时冲击力小等优点,满足自动化设备的工作要求。综上所述,本文针对推进机的主传动机构,从尺寸参数设计与齿廓修形两方面进行了优化改进,提高了机构的整体平稳性,减小了振动冲击。结论可为齿轮-连杆机构的设计与研究提供理论参考依据。更多还原

【Abstract】 With the wide application of automatic production line in the intelligent manufacturing,the influence of its whole machine’s stability on the processing quality of the products is becoming more and more obvious.The pusher,also known as feeder,is an important part of automatic production line,its motion stability directly affects the performance of the whole machine.In this paper,the pusher of a capsule automatic production line is taken as the research object.The multi-objective optimization design based on NSGA-Ⅱ genetic algorithm is used in the gear-linkage mechanism to improve the motion stability of mechanism,under considering comprehensively the influence of kinematics characteristics and gear’s meshing characteristics.Then the influence of the profile modification parameters on mechanism’s transmission characteristics is discussed.The main work and conclusions are as follows:Firstly,the crank-gear-rack mechanism is employed as the main drive mechanism of pusher according to the work requirements,in order to realize the pusher’s function of auto-commutation and long-distance transmission without changing the revolving speed of the motor.The mathematical analysis model of the mechanism is established by taking the gear angle,the gear angular acceleration and the contact ratio of gear-rack as optimization objectives,based on the requirements of mechanical kinematic characteristics and the gears’ mesh characteristics.By using the NSGA-Ⅱ algorithm,the multi-objective optimization of the parameters is carried out and a set of optimal solution is obtained.In the meanwhile,the optimal design scheme is determined.The kinematic characteristics are analyzed to the fore-optimized and post-optimized mechanism on Matlab.The results show that: in the promise of ensuring mechanical smooth operation,the swing angle of gear is increased from 7.365 rad to 9.875 rad,which improves the ability of reciprocating motion with long stroke to the mechanism.Secondly,by combining ANSYS finite element technology with ADAMS virtual prototype technology,the rigid-flexible coupling dynamics simulation of optimized mechanism is carried out.The maximum tooth modification value is determined based on the finite element contact analysis,and two kinds of modification methods with long and short modification are proposed.Then from the perspective of statics and dynamics,the effects of the two kinds of methods on gears’ meshing characteristics are analyzed and discussed under different load conditions.The results show that the short modification method is more suitable for the gears in this paper,and the modification length is 1 mm,modification value is 0.02 mm.Modified gear’s meshing impact is reduced obviously and the stationarity of the whole mechanism is improved.Finally,the rationality of the pusher’s structure is verified from three aspects: the natural frequency of the gearbox,the static characteristics of the output shaft and the simulation of the propulsion process.At the same time,the comparison is carried out about contact situation between mold and push claw at the initial moment under three push approaches,including constant speed,fore-optimization pusher and post-optimization pusher.The results show that: the structure of the designed pusher can work reliably,the pusher has the advantages of stable acceleration,smooth motion and small impact force at the initial moment,which is satisfied the work requirements of the automatic equipment.In summary,the optimization of pusher mechanism is carried out from two sides: the design of the dimension parameters and the tooth profile modification,which improved the overall stability of the mechanism and reduced the vibration shock.The research results can provide the theoretical reference for the design of gear-linkage mechanism.更多还原