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Unformatted text preview: 1 Chapter 11 1. Summer 2. Comparator 3. Block Blocks in Series are equivalent to... G(s)X(s) Y(s) = Chapter 11 2 Chapter 11 Figure 11.10 Three blocks in series. Figure 11.11 Equivalent block diagram. 3 Chapter 11 Block Diagram Reduction In deriving closedloop transfer functions, it is often convenient to combine several blocks into a single block. For example, consider the three blocks in series in Fig. 11.10. The block diagram indicates the following relations: 1 1 2 2 1 3 3 2 (1111) X G U X G X X G X = = = By successive substitution, 3 3 2 1 (1112) X G G G U = or 3 (1113) X GU = where 3 2 1 . G G G G @ 4 Chapter 11 Figure 11.8 Standard block diagram of a feedback control system. 5 Chapter 11 ClosedLoop Transfer Functions The block diagrams considered so far have been specifically developed for the stirredtank blending system. The more general block diagram in Fig. 11.8 contains the standard notation: Y = controlled variable U = manipulated variable D = disturbance variable (also referred to as load variable) P = controller output E = error signal Y m = measured value of Y Y sp = set point internal set point (used by the controller) sp Y = % 6 Chapter 11 Y u = change in Y due to U Y d = change in Y due to D G c = controller transfer function G v = transfer function for final control element (including K IP , if required) G p = process transfer function...
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This note was uploaded on 09/22/2009 for the course CHEMICAL CHE 401 taught by Professor Dr.muhammadalarfaj during the Spring '09 term at King Fahd University of Petroleum & Minerals.
 Spring '09
 Dr.MuhammadAlArfaj

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