多工序加工系统产品尺寸误差传递建模

Modeling of Dimensional Errors Propagation in Multi-stage Machining System

多工序加工系统中最终产品的尺寸误差是所有加工工序上尺寸误差累积、耦合与传递的结果。目前方法是建立数学模型对多工序加工系统尺寸误差传递进行分析,而缺乏逻辑层次上的建模理论和方法。为解决多工序加工系统中尺寸误差传递的逻辑分析问题,采用面向对象Petri网方法,在定义误差状态通用物理对象基础上,建立通用物理对象和加工系统的映射规则,对误差状态子类物理对象进行继承和封装,设计出误差状态消息传递关系网。建立的产品尺寸误差面向对象Petri网(Errors of product dimension-object oriented Petri net,EPD-OPN)模型可以作为多工序加工系统中尺寸误差传递动态分析和故障诊断依据。通过发动机缸盖的多工序加工过程为例证明该模型的有效性和可行性。该模型具有模块化、可重复使用性的特点和结构化的复杂逻辑关系描述能力,是目前数学模型很好的扩展。

Dimensional errors of the final product are determined by stack-up,coupling and propagation of dimensional errors from all operations in multi-stage machining system.In order to analyze logically the dimensional errors propagation in multi-stage machining systems,object-oriented Petri net is used.Based on defining generic objects of error states,the rules of mapping generic objects into machining system are developed.Then subclass objects of error states are derived and encapsulated from generic objects.Finally,relation nets of errors states message transmission are designed.The errors of product dimension-object oriented Petri net（EPD-OPN） model can be used as a tool to analyze the error propagation.The effectiveness and feasibility of the model is validated through a cylinder head machining process.The developed model has some excellent characteristics,such as modularization,reusability,and capability to describe structural logical relationships.