Classical Frequency-Domain Design Methods
The design of feedback control systems in industry is probably accomplished using frequency-response (FR) methods more often than any other. Frequency-response design is popular primarily because it provides good designs in the face of uncertainty in the plant model (G(s) in Fig. 1). For example, for systems with poorly known or changing high-frequency resonances, we can temper the feedback design to alleviate the effects of those uncertainties. Currently, this tempering is carried out more easily using FR design than with any other method. The method is most effective for systems that are stable in open loop; however, it can also be applied to systems with instabilities. This section will introduce the reader to methods of design (i.e., finding D(s) in Fig. 1) using lead and lag compensation. It will also cover the use of FR design to reduce steady-state errors and to improve robustness to uncertainties in high-frequency dynamics.
KeywordsFrequency response FR Magnitude Phase Bode plot Stability Bandwidth Phase margin PM Gain margin GM Crossover frequency Notch filter Gain stabilization Amplitude stabilization
- Franklin GF, Powell JD, Workman M (1998) Digital control of dynamic systems, 3rd edn. Ellis-Kagle Press, Half Moon BayGoogle Scholar
- Franklin GF, Powell JD, Emami-Naeini A (2010) Feedback control of dynamic systems, 6th edn. Pearson, Upper Saddle RiverGoogle Scholar
- Franklin GF, Powell JD, Emami-Naeini A (2015) Feedback control of dynamic systems, 7th edn. Pearson, Upper Saddle RiverGoogle Scholar