PID tuning

The two Ziegler-Niehols PID tuning methods provide a useful rule of thumb empirieal approaeh. The eontrol system design teehniques diseussed in Chapters 5 and 6 however will generally yield better design solutions. 

An optimal model-based PID tuning method for the control of poly-butadiene latex reactor... 

Numerous empirical correlations have been developed to determine PID tuning parameters for load responses of processes. These correlations are based either on closed-loop procedures, which directly identify the ultimate gain and ultimate period of the loop, or on open-loop procedures, which identify the time... 

Figure 9,7 Common performance criteria for PID tuning techniques. The peak overshoot is the ratio A/B, C/A is the decay ratio, and T is the period of oscillation.

In this section, we decide on exactly which two frequencies to use in Equations (6.52)-(6.54) in order to solve for the PID controller parameters. Our ultimate objective is to produce a PID controller that achieves a close match between the actual and desired closed-loop performemce in the time domain. Which frequencies to use for PID design has been and remains an interesting question. The well-known Ziegler-Nichols frequency response PID tuning method is based on the crossover frequency of the process. However, we have found that, although the crossover frequency is very important from a stability point of view, lower frequencies are far more important from a closed-loop performance point of view. 

This chapter introduces new PID tuning rules, derived from the general PID design method proposed in the previous chapter, for frequently encountered first order plus delay processes and integrating plus delay processes. 

This chapter consists of five sections. Section 7.2 presents the development of the PID controller tuning rules for first order plus delay processes. Sections 7.3 and 7.4 illustrate the new tuning rules using simulation and experimental studies, respectively, and compares the results with those obtained using the IMC-PID tuning rules. Section 7.5 presents the development of the PID tuning rules for integrating plus delay processes. 

Tb derive the PID tuning rules, we write the Y function defined in Equation (6.36) in terms of the scaled variable s (or w = dw)... 

Figure 7.14 Stability margins for PID tuning rules (solid (( — 1 solid with o C = 0.707J. Upper diagram gain margins lower diagram phase margins...

A comparison of PID tuning relations in Section 12.6 and an introduction to the important practical problem... 

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