Modeling Plants and Processes for Control Systems
It is useful to remind ourselves of the main tasks of an industrial control system which is liable to operate in a noisy and polluted environment subject to unpredictable disturbances such as fluctuating temperatures, humidity, and electrical line voltage transients. The first task of an industrial controller is to suppress the influence of such external disturbances by changing the over-all system characteristics in order to compensate for the unfavorable effects mentioned. Secondly, the controller must ensure the stability of the plant or process under varying operational conditions. If as a result of some an external factor one of the state variables deviates from its operating point but returns to it in time, then the process is deemed stable. The controller must influence the process such that this will happen under all operating conditions. Thirdly, the controller must ensure the optimum performance of the plant or process by producing the largest amount of the output product. Maximum productivity is particularly important in the chemical industry where profits depend on the quantities of output produced. It is clear that the control system designer must know the operating characteristics of the process as well as all possible operating conditions in order to carry out his work successfully. This process knowledge can take various forms, as outlined in the following sections.
KeywordsFuzzy Logic Fuzzy Control Fuzzy Controller Fuzzy Logic Controller Industrial System
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