Mieczysław Metzger

Over the past two decades decentralised, distributed control systems appear as a well-agreed standard in the automatic control. The big world producers offer very expensive, different communication network systems for all layers of control. One of the most important steps in the development of real-world control system is this system testing. Control software and control equipment can be tested on the real-time simulators. However, the most important tests should be carried out on the real-world plants. Although testing control equipment on the semi-industrial scale pilot plants is more expensive than on the simulators, it is also more realistic.

A big effort was made over the last years in the CSCE group for design, development and building of semi-industrial scale pilot plants treated as real-world control plants. All of these plants include real-world professional industrial measurement and control equipment. The control equipment allows developing distributed control systems basing on operating, control and device levels of data transmission.

In the CSCE group we start building two real-world distributed control systems. Both are designed for control of our pilot plants.

The first system (see Fig.1) is based on hardware and software from the National Instruments. This system exerts only one standard of data transmission based on the Ethernet. The SS2 Switch 3300/100Mhz equipment allows communication with an application of TCP/IP and UDP protocols. Three FieldPoint type controllers and appropriate data acquisition boards allow distributed control and monitoring. The system can be programmed with an application of the LabVIEW standard, and that is why it will be very user-friendly for research and teaching. The supervisory information system, presented in Fig. 1, will be an experimental plant for comparative investigations of transmission possibilities.

The second system (see Fig. 2) is based on another idea. Namely, it is an industrial system from one of the world's most-developed systems from a big producer. The Logix system from Rockwell-Allen-Bradley includes three controllers: one ControlLogix and two FlexLogix as well as one Flex I/O for distributed data acquisition. The Rockwell system includes three-level open architecture of data transmission: namely, the information, control and device levels. The Ethernet, ControlNet and DeviceNet standards offer services for these levels respectively. Although the hardware and the software of the Logix system demand more sophisticated knowledge but also show the problems in the area of designing real-world, multi-level-network distributed control systems.

Distributed control system based on the FieldPoint standard

Figure 1. Distributed control system based on the FieldPoint platform.

 

Distributed control system based on the Logix platform

Figure 2. Distributed control system based on the Logix platform.

 

Over the last two years the appropriate control and information equipment has been completed. Both systems were designed in the form presented in Fig. 1 and Fig.2, and we start with integration and carrying out these systems.