Process control integral response

Chapter 22 provides equations for typical process controllers and control valve dynamics. The controllers considered are the proportional controller, the proportional plus integral (PI) controller and the proportional plus integral plus derivative (PID) controller. Integral desaturation is an important feature of PI controllers, and mathematical mc els are produced for three different types in industrial use. The control valve is almost always the final actuator in process plan. A simple model for the transient response of the control valve is given, which makes allowance for limitations on the maximum velocity of movement. In addition, backlash and velocity deadband methods are presented to model the nonlinear effect of static friction on the valve. 

Economics in process control, 3, 10-11, 15, 26, 532-34 Environmental regulations, 3 Equal-percentage valve, 254, 255 Equations of state, 57 Equilibria, 56, 78 chemical, 56 phase, 56-57, 71, 75, 78 Error criteria (see Time integral criteria) Euler s identities, 131-32, 149 Experimental modeling, 45, 656 frequency response techniques, 668 process identification, 657-62 time constant determination, 228, 232 Exponential function, 130 approximations, 215-16 Laplace transform, 130 z-transform, 592... 

To illustrate the influence of each control mode, consider the control system responses shown in Figure 9.4. These curves illustrate the typical response of a controlled process for different types of feedback control after the process experiences a sustained disturbance. Without control the process slowly reaches a new steady state that differs from the desired steady state. The effect of proportional control is to speed up the process response and reduce the offset. The addition of integral control eliminates offset but tends to make the response more oscillatory. Adding derivative action reduces the degree of oscillation and the response time, ... 

RCS version control, 186, 248, 256, 306, 308-309 details, 310-313 repeat statement, 118 repulsion integral processing, 142-147 response matrix, 637 Restricted Hartree-Fock, see RHF Restricted open-shell Hartree-Fock, see ROHF reverse dictionary order, 275, 449 (R)GUHF, see GUHF RHF, 314 Ring, P., 630 ROHF, 407 RPA, 621-628 history of name, 629 Rumer, G., 542n Rys polynomials, 228n, 233... 

Proportional-plus-integral control is the most generally useful control mode and therefore the one usually applied to automated process-control. Its major limitation is in processes with large dead-time and capacitance if reset time is faster than process dead-time, the controller-response changes are faster than the process, and cycling results. In these cases, derivative control is beneficial. 

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