冲压液压机PLC程序设计中的时序逻辑对象封装

Succession Logic Objects Encapsulated in PLC Programming of Hydraulic Stamping Press

提出时序逻辑对象的概念。通过创建和封装时序逻辑对象并按面向对象方法进行电液比例控制系统的PLC编程,把对冲压液压机设备实体的控制映射为控制虚拟逻辑对象。根据流程图中的状态顺序及电磁铁闭合表中液压泵阀等元件的分布,按工艺要求将液压元件组合成时序逻辑对象;每个对象均有各自属性,包括运动机构在相应工步下的工作压力、流量、位置和方向等极限参数;事件则是报警信息、控制模式、工艺制式、操作命令和反馈信号的组合逻辑。对象间传递的消息按流程状态顺序由上游向下游传递并从下游对象得到回复消息;逻辑对象支持的方法由流程状态定义确定。该对象抽象和封装方法结合消息传递和触发机制可以提高编程效率。

A concept of succession logic object has been presented in object-oriented methodology.By succession logic objects created and encapsulated,PLC program could be designed for electro-hydraulic proportional control system.Then controlling actual devices has been mapped as controlling virtual logic objects in hydraulic stamp- ing press.According to the order specific control task required in operation procedure,related valves and pumps have been extracted from electromagnet close-open table and encapsulated into a succession logic object each of which with private attributes and methods,including pressure,direction and other limiting parameters of devices while the methods depending on function definitions in procedure.The events have been combinatory logic of alarm,control pattern, process mode, operational command and feedback signals.The objects have been assigned to send messages, receive and be responsible to the events.As the message mechanism works,such programming approach can complete control task efficiently.