Multivariable and Supervisory Control

Unlike what is shown in Table 9.5, strictly speaking, we should mention that a pure proportional control cannot reach the set point with an accuracy of 100 % it only reaches a value close to the set point, where the remaining difference is known as the offset. 

In the search for greater efficiency in the ability of controllers to control processes, the proportional term is complemented by an integral expression and another, derivative, expressimi. In future courses, you will learn about this improvement and about controller tuning. 

The valve actuation PAHv-102 is governed by a binary control logic PAH programmed in controller-102. Binary means that there are only two possible states of the actuator, open or closed. As mentioned previously, the valve will open to 100 % if the pressure inside the tank E-102 becomes equal to or greater than 100 [bar] otherwise, the valve will remain open 0 % (or 100 % closed). This can be represented as a piecewise function, composed as follows  

Pressure 100 bar then valve is open In graphical terms, the behavior of the valve is depicted in Fig. 9.8. 

In the examples of controlled processes that we have been discussing, we have worked with systems handling one resource and with one target variable, i.e., single-input/single-output (SISO) systems. However, in actual practice, the process is affected by multiple input variables and has multiple target variables, i.e., a multiple-input/multiple-output (MIMO) system. 

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