FIGURE 12.1 Two variable process-control loops that interact. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson.

FIGURE 12.1 Two variable process-control loops that interact.

Curtis JohnsonProcess Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 12.2 A compound system for which the ratio of two flow rates is controlled.




FIGURE 12.3 Circuit for Example 12.1.




FIGURE 12.4 General features of a cascade process-control system.




FIGURE 12.5 Cascade control often provides better control than direct methods.




FIGURE 12.6 Flowchart for an interactive control problem.




FIGURE 12.7 Loop disturbances can occur from intentional setpoint changes or changes in process load.




FIGURE 12.8 Instability in a process-control loop refers to the uncontrolled growth of the controlled variable.




FIGURE 12.9 Tuning determines the reaction of a controlled variable to changes.




FIGURE 12.10 In one type of cyclic response, the system is adjusted to make each peak down to one-quarter of the previous peak.




FIGURE 12.11 The minimum-area tuning response characteristics.




FIGURE 12.12 Error versus time for Example 12.4.




FIGURE 12.13 A transfer function changes the amplitude and phase of a sinusoidal input.




FIGURE 12.14 This control loop has been opened so that the effect of a disturbance on the loop can be traced.




FIGURE 12.15 This figure suggests how an initial transient oscillation can grow under the appropriate feedback conditions.




FIGURE 12.16 A Bode plot shows the open-loop gain and phase versus frequency of an applied sinusoid.




FIGURE 12.17 Process-reaction graph for loop tuning.




FIGURE 12.18 Process-reaction graph for Example 12.7.




FIGURE 12.19 Bode plot for Example 12.9.




FIGURE 12.20 Bode plots showing proportional, integral, and derivative mode contributions.




FIGURE 12.21 Bode plots for Example 12.11. The proportional mode does not affect phase.




FIGURE 12.22 Circuit for Problem 12.6.




FIGURE 12.23 Process-reaction graph for Problem 12.8.




FIGURE 12.24 Bode plot for Problems 12.10 and 12.11.




FIGURE 12.25 Bode plot for Problem 12.13.








FIGURE 12.27 Process-reaction graph for Problem 12.16.








FIGURE 12.29 Process-reaction graph for Problem S12.1.




FIGURE 12.1 Two variable process-control loops that interact. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson.

Documents