Digital control systems

The Turbolog DSP digital control system was installed to meet these requirements. This system is based on off-the-shelf hardware that is adapted to this application, running GHH-Borsig s custom-designed... 

Figure 7.13 shows the general form of a digital control system. The pulse transfer function of the digital controller/compensator is written... 

This tutorial looks at the application of MATLAB to digital control system design, using the problems in Chapter 7 as design examples. 

This is a closed-loop digital control system as shown in Figure 7.14, with a plant transfer function... 

Example 7.6 constructs the root-locus in the z-plane for the digital control system in Example 7.4 (Figure 7.14). 

Kuo, B.C. (1980) Digital Control Systems, Holt, Rinehart and Winston, Inc., New York. 

Distributive Control System (DCS) is a digital control system that has a distributive architecture where different control functions are implemented in specialized controllers. 

It may be useful to point out a few topics that go beyond a first course in control. With certain processes, we cannot take data continuously, but rather in certain selected slow intervals (c.f. titration in freshmen chemistry). These are called sampled-data systems. With computers, the analysis evolves into a new area of its own—discrete-time or digital control systems. Here, differential equations and Laplace transform do not work anymore. The mathematical techniques to handle discrete-time systems are difference equations and z-transform. Furthermore, there are multivariable and state space control, which we will encounter a brief introduction. Beyond the introductory level are optimal control, nonlinear control, adaptive control, stochastic control, and fuzzy logic control. Do not lose the perspective that control is an immense field. Classical control appears insignificant, but we have to start some where and onward we crawl. 

All of the control schemes mentioned previously can be accomplished using digital control or the traditional analog control methods. For many processes there is at present no economic justification for a digital control system if only physical disturbances are to be considered. One exception to this is a multiproduct batch processing plant, in which a number of operations are required. 

The name is also used by Nippon Shokubai Company as a trade name for distributed digital control systems for chemical plant. 

Direct digital control systems appeared in the mid-1980s and displaced older analog closed-loop schemes for temperature control. These digital systems improved both accuracy and reliability. The earlier systems were modeled after existing system architectures and did not contain intelligent, standalone field devices. There were numerous interfaces to the various building systems and the major decisions were made at a central computer. 

Specialists study this case of cyber-terrorism because it is the only one known in which someone used a digital control system deliberately to cause harm. The former employee s intrusion shows how easy it is to break in—and how restrained he was with his power. 

Figure 18.3h shows a DDC (direct digital control) system. All the control calculations are done in the digital computer. The computer outputs go, through holds, directly to the control valves. 

Pilot-plant experiments have been carried out at real process conditions in the coke plant August Thyssen (Duisburg, Germany). The DN 100 pilot column (Fig. 9.11) was made from stainless steel and equipped with about 4 m of structured packing (Sulzer MELLAPAK 350Y), three liquid distributors, and a digital control system. Several steady-state experiments have been compared with the simulation results and supported the design optimization of the coke gas purification process [91]. 

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