The Research And Realized Of The Control Software For Field Control Station In DCS

Distributed control system (DCS) has two obvious advantages: centralized monitoring and dispersing risk. The development of computer technology, communication technology, display technology, control technology and manufacture process improved the reliability of DCS. Therefore, DCS are widely applied in various industrial control. Field control station, as the core component of DCS, must satisfy the the requirements of real-time and high reliability. Its main functions: collecting and processing the field date, data transmission and network communication, the implementation of control plan , etc.Network communication is the nerve center of the whole control system. Based on QNX operating system, this paper realizes the system network (SNet) of DCS field control station. In SNet, we realized the communication between multiple control stations, master and slave control templates, control station and operation station, making use of the communication technology of broadcast and multicast. The different data information were transmited in different communication ways, in order to ensure the real-time and reliability of the system.The control algorithm is the kernel of the control system.In DCS control software, using of configuration files and dynamic-link librariest this paper realized FBD function block diagram. A simple fuzzy PID control algorithm is designed and realized, through the learning and compareing many kinds of control algorithm such as PID control, the fuzzy control and so on. This algorithm apply to some certain occaisons,such as when it's difficult to tune the parameters of PID control and when t operators have lower ability. Through the facture-debugging, it proved that the algorithm is simple to implement and operation convenient, and can meet the demand of practical production process better.This control system supports the parallel running of multiple control programs. However, when a large number of function block having different cycles run at the same in actual operation of the DCS, it is difficult to meet the requirement of parallelism and real-time. Therefore, it needs the pre-processing of the programs which is ready for run. In view of this situation, this paper designed and realized a non-preemptive task scheduling algorithm base on phase shift. The experiment indicated that this method is simple and easy to realize ,and it could guarantee the real-time and the parallel of the user programs.