摘要
影响平面单环闭链结构装配精度的主要误差源有杆件加工偏差、装配约束误差以及铰链间隙。而铰链间隙的随机性导致平面单环闭链结构装配误差具有不确定性。为了能够实现装配精度预测和获得装配误差边界,通过分析平面单环四杆结构装配特点,提出单杆件固定和双杆件连接两种装配单元,并建立两种单元的误差模型。在此基础上,完成了无间隙平面单环闭链结构装配误差建模。然后通过引入连杆机构旋转法则,以虚拟杆件表征铰链间隙并将其视为"短杆",从而基于杆件旋转不变性建立了考虑间隙的平面单环闭链结构装配误差不确定性分析模型,并给出了装配误差边界计算方法。最后以平面五杆单环结构作为数值案例,验证了所提出方法与模型的可行性与实用性。
The link deviation, assembly constraint error and joint clearance are the major error sources, which affect the assembly accuracy of planar single-closed-loop mechanisms. However, the randomness of joint clearance results in the accuracy uncertainty of the planar single-closed-loop mechanism. In order to predict the assembly accuracy and obtain the error bound, two assembly components, single-fixed link and two-connected link, are proposed and their error models are established by analyzing the assembly property of a planar four-bar single-loop mechanism. And accordingly, the error modeling of assembly error of the single-loop mechanism without considering joint clearance is firstly completed. Then the uncertainty analysis model of assembly error of the planar single-loop mechanism is built by introducing the rotatability law of the linkage, in which the joint clearance is regarded as a ‘short link'. In addition, the method of calculating the bound of assembly error is given. At last, the feasibility and utility of the method proposed above are verified by a numerical example of the planar five-bar single-loop mechanism.
引文
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