基于真实机器的装配公差分析方法

机器上目标要素的位置误差是零件几何误差和装配误差共同作用的结果．为了研究装配基准的几何误差在装配链中的传递和变换，提出基于真实机器模型的装配积累误差建模与分析方法．首先，采用控制点变动模型表示零件几何要素，利用蒙特卡罗模拟方法生成几何要素相对于公称位置的变动实例．然后，根据理论正确尺寸确定几何要素相对于基准参考框架的公称位置．第三，提出基准参考框架建立方法，根据基准要素实例确定目标要素的测量基准参考框架．最后，提出装配接触模型，根据装配顺序和基准要素位置实例确定测量基准参考框架相对于装配基准体系的位置．通过以上4个过程计算装配链中所有关联要素在机器坐标系下的位置，获得装配基准体系的几何误差在装配链中的转递和变换关系．将真实机器装配情况模拟分解为4个模块化过程，可以实现装配误差分析的自动化．以三平面定位的轴孔装配的装配间隙计算为实例，验证了本文提出的方法．

Assembly tolerance analysis method based on the real machine model

The position errors of an objective feature of a machine is affected comprehensively by the geometric errors and assembly errors of the parts on the assembly chain. In order to investigate the effect of assembly datum errors on the transformation and propagation of the geometric errors in an assembly chain, a modeling and analysis method of assembly error accumulation based on the real machine model is proposed. In this approach, the calculation process of the real position of geometric feature is consist of four steps. Firstly, the deviation geometric feature are represented by the control point variation model, and the deviations of geometric feature from its normal position are simulated by the Monte Carlo method. Secondly, the normal position of the deviation geometric feature in the datum reference frame （DRF） is determined by theoretical dimension. The third step, the DRF establishment method is proposed, and the measure DRF of the objective feature is established with the datum geometry example. The fourth step, the assembly contact model is proposed, the relationship between the measure datum reference frame and assembly datums is calculated according to the assembly sequence and the deviation geometry example of assembly datum surface. The real position of all related parts on the assembly chain in machine coordinate system are calculated by above procedures, and the transformation and propagation of the geometric errors of assembly datum in an assembly chain are obtained. The procedure to simulate the real machine assembly is decomposed into four modular processes, which is useful in realizing the automation of assembly error analysis. A assembly error accumulation example of pin-hole assembly with the three orthogonal datum planes is investigated, and the proposed approach is verified.