School of Control and Computer Engineering, North China Electric Power University, Changping District, Beijing, 102206, China.
ISA Trans. 2012 Jan;51(1):170-80. doi: 10.1016/j.isatra.2011.07.007. Epub 2011 Sep 1.
Communication efficiency is lowered and real-time performance is not good enough in discrete control based on traditional WorldFIP field intelligent nodes in case that the scale of control in field is large. A soft PLC system based on WorldFIP fieldbus was designed and implemented. Link Activity Scheduler (LAS) was integrated into the system and field intelligent I/O modules acted as networked basic nodes. Discrete control logic was implemented with the LAS-integrated soft PLC system. The proposed system was composed of configuration and supervisory sub-systems and running sub-systems. The configuration and supervisory sub-system was implemented with a personal computer or an industrial personal computer; running subsystems were designed and implemented based on embedded hardware and software systems. Communication and schedule in the running subsystem was implemented with an embedded sub-module; discrete control and system self-diagnosis were implemented with another embedded sub-module. Structure of the proposed system was presented. Methodology for the design of the sub-systems was expounded. Experiments were carried out to evaluate the performance of the proposed system both in discrete and process control by investigating the effect of network data transmission delay induced by the soft PLC in WorldFIP network and CPU workload on resulting control performances. The experimental observations indicated that the proposed system is practically applicable.
在基于传统 WorldFIP 现场智能节点的离散控制中，当现场的控制规模较大时，通信效率降低，实时性能不够好。设计并实现了一种基于 WorldFIP 现场总线的软 PLC 系统。将链路活动调度器（LAS）集成到系统中，现场智能 I/O 模块作为网络化的基本节点。离散控制逻辑是通过集成 LAS 的软 PLC 系统来实现的。所提出的系统由配置和监控子系统以及运行子系统组成。配置和监控子系统采用个人计算机或工业个人计算机实现；运行子系统基于嵌入式硬件和软件系统进行设计和实现。运行子系统中的通信和调度采用嵌入式子模块实现；离散控制和系统自诊断采用另一个嵌入式子模块实现。提出了系统的结构。阐述了子系统设计的方法。通过研究软 PLC 在 WorldFIP 网络中引起的网络数据传输延迟以及 CPU 工作负载对控制性能的影响，对离散控制和过程控制中的系统性能进行了实验评估。实验观察表明，该系统具有实际应用价值。
