基于控制及信息协议的计算机监控通信软件

Communication software based on control and information protocol for supervisory control system

为使车间监控计算机通过以太网实现与PLC的可靠通信,选用以太网工业协议作为监控通信协议。分析了以太网工业协议的层次结构,指出CIP(控制及信息协议)中的显式消息传递方式适合作为监控计算机和PLC通信的协议。通信软件被设计为两层——基于以太网的CIP通信类和基于CIP通信类的监控通信类。CIP通信类提供了读写PLC各种内存变量的接口函数,采用互锁机制避免多线程操作中潜在的资源竞争冲突问题。监控通信类为应用程序提供向PLC发送命令和从PLC读取报告的接口函数和PLC状态的订阅服务。开发的通信软件已在某货物柔性处理线监控系统中应用。

To provide reliable approach for the supervisory computer to exchange control data with the PLC in workshop via Ethemet, Ethemet/Industrial protocol is chosen as the communication protocol. The hierarchical structure of Ethernet/Industrial Protocol is analyzed. It is figured out that explicit messaging in control and information protocol （CIP） is suitable for the supervi- sory computer communicating with PLC. Communication software is designed as two layers, which are Ethernet-based CIP com- munication class and supervisory-control communication class based on CIP communication class. CIP communication class pro- vides functions of reading and writing variables in PLC memory, and adopts interlock mechanism to prevent the possible conflicts caused by the sharing of network resource. Supervisory-control communication class provides the supervisory-control software with services of sending commands to the PLC and reading reports from the PLC. The software also provides subscription services of the reports form the PLC. The communication software is used in the supervisory control system of a flexible trans- porting line.