Development And Optimization For Virtual DPU Based On IEC61131-3

DCS(Distributed Control System) plays an important role in industry area, such as electric power, metallurgy and petrochemicals and so on. Virtual DCS is designed to represent the real distributed control system as real as possible in a normally open platform for computer information management system. The virtual DPU(Disrtibuted Process Unit) based on IEC61131-3 standard is the most important part in virtual DCS. Virtual DPU software development is based on MFC, create a logical mapping between DPU physical structure and software models based on IEC61131-3 standard, and use an object-oriented design method to develop virtual DPU to realize configuration file parsing and control operation functions.The task of virtual DPU includes two sides:realize the communication function of virtual DCS and reappear the control function of real DPU. On the communication function side, virtual DPU and the object model library are connected by Socket and DCOM on client/server mode, which are two kinds of distributed communication, and take them into comparison. On the side of reappearing the control function of real DPU, scheduling function block according to the correct order based on configuration information is the key to realize the function of virtual DPU. The virtual DPU obtains configuration information by parsing configuration files, and memories link relationships based on graph theory. Finding all the loop information without reduplicating based on depth-first-search. According to the link relationship of nodes, when adding nodes in a tree structure, nodes in the loop which meet some conditions will take special action to generate function block tree without reduplicate nodes. Using post-order traversal to gain the correct schedule order of virtual DPU. Taking typical single input single output control system for an example, this paper accomplishes virtual DPU load files remotely, gain configuration information and memory the link relationship and dispatch module by function block library and object model library on a correct order.