基于QNX的地铁供电监控系统实时性分析及实现

Analysis and implementation of real-time performance for QNX-based subway PSCADA system

介绍了广州地铁3号线供电监控(PSCADA)系统及其重要组成部分总控单元的功能、结构、内部联系:重点分析总控单元中各项任务的实时性需求,根据设计时限要求,即遥信变位至信息送达调度中心不超过2 s,遥控执行成功不超过3 s,而遥测更新10 s左右即可,确定遥信、遥控数据处理为系统关键任务,必须优先处理;结合ONX在实时性方面的优势、特点,通过采用多项关键技术,如提供不同服务质量(QoS)的双数据通道模式,设置RR、FIFO实时调度策略,分配不同的线程优先级,集成ONX特有的脉冲消息机制,以及其他传统IPC方式等,加快了系统对重要事务的响应速度,增强了软件的实时性、可靠性和可用性。该设计方案已在实际工程应用中获得满意效果。

The PSCADA （Power Supervisory Control And Data Acquisition） system of Guangzhou Subway Line 3 and its important component GCU （General Control Unit） are introduced,including its function, structure and internal communication. The real-time performance of different tasks in GCU is analyzed in detail. As the time delay from remote signal change to dispatch center acceptance is specified not over 2 s,the execution time of remote control not over 3 s and the updating period of remote measurement around 10 s,the remote signalling process and remote control process are identified as key tasks with higher priority. Applying the key technologies of QNX in real-time processing,such as the dual data channel mode with different QoS（Quality of Service）,the real-time schedule policies of RR and FIFO,the various thread priority assignment,the integration of QNX unique pulse message mechanism with traditional IPC methods,etc. ,the response speed of important tasks is increased and the real- time performance,reliability and availability of software are improved. This design has put into practical engineering application with good results.