【作者】 李小燕；

【导师】 李团结；

【作者基本信息】 西安电子科技大学 ， 机械设计及理论， 2008， 硕士

【摘要】 在机械系统中,运动副是机构构件连接的中间环节,它不仅要将构件连接起来还要保证构件间能有一定的相对运动。运动副元件间一般需要采用动配合,这就必然存在一定的运动副间隙。为此,本论文对考虑间隙的平面四杆机构动力学问题和仿真方面进行了分析和研究。首先介绍了机构动力学中的运动副间隙模型的近期研究成果,遇到的主要问题和未来的发展趋势。详细的阐述了运动副间隙模型中的“二状态”和“三状态”模型的建模方法。针对运动副间隙对四杆机构的运动影响,选择了“连续接触模型”进行分析。并以考虑单一间隙的平面四杆机构为例,建立存在间隙的运动微分方程,通过数值积分求出一个运动周期的解,从而确定运动副元素的分离判断准则。同时对平面四杆机构动力学特性进行了分析,比较了理想无间隙与考虑间隙机构的不同动态特性。为了进一步的研究间隙运动副的动力学特性,对单一的间隙转动副和移动副系统进行分析,建立动力学微分方程。对不同间隙值,不同接触阻尼系数下的间隙运动副的接触力动态特性进行了仿真分析。同样利用“连续接触模型”对考虑多间隙的平面四杆机构进行了分析,其中,考虑每个运动副处均存在间隙,研究存在四个间隙的平面四杆机构的运动特性,利用完整系统的拉格朗日方程建立了机构的动力学方程组,用龙格-库塔法编制了求解该微分方程组的求解程序,对四杆机构的动态性能参数进行了仿真分析。从而说明运动副间隙大大影响了机构的运动特性,使机构的实际运动和理想运动之间产生偏差,并且使运动副之间产生碰撞,从而引起构件的振动,加速磨损,降低工作效率。更多还原

【Abstract】 The joints which connect two mechanic components of mechanisms can make sure the machines move relatively. Therefore, the presence of clearance in the joints of mechanisms must be considered. The clearance can cause contact and separation between the joint elements. So that, there will cause windages between the ideal movements and practical movements, increase the force between two machine elements. Then internal dynamic contacts can cause unusual vibration and noise, accelerate fatigue and wear and seriously reduce the machine efficiency. So, the influence of machine with clearance can not be neglected to some machine systems. So this work mainly studies the analysis of dynamic model and simulation of a deployable truss structure with clearances.Firstly, recent researches were reviewed and discussed, several typical dynamics model of pairs with clearances were compared and discussed in respect of impact, damping, friction, etc in detail. Expound the“two-state”and“three-state”clearance model particularly. Considering the influence of machine with clearance,chose the continous contact model to analyse. On the basis of analysis for planar four-bar linkages with clearances, the dynamic differential equations were established. The numerical analysis methods were used to solve the problems, so that the impact-separate rule for the elements of joints were established, meanwhile, compared the dynamic characteristics of mechanisms between clearance considered and no-clearance considered. To be continue, two typical joints with clearance were established, the rotate joint and the remove joint, analysed their dynamics differential equations, compared the dynamic charateristics with different clearances, different damp, some important conclusions were drown. Finally analyse the planar linkages with four clearances using the continuous contact model, established the dynamic differential equations using Larange equations. By solving these problems, which not only show the bad effects clearances have on the stability of mechanism, but the methods to reduce the effects as well.更多还原