Choosing a Frequency-Domain Analysis Command

When you perform time-domain analysis of a dynamic system model, you may want one or more of the following:

  • A plot of the system response as a function of frequency, or plots of pole and zero locations.

  • Numerical values of the system response in a data array.

  • Numerical values of characteristics of the system response such as stability margins, peak gains, or singular values.

Control System Toolbox™ frequency-domain analysis commands can obtain these results for any kind of dynamic system model (for example, continuous or discrete, SISO or MIMO, or arrays of models).

To obtain numerical data, use:

  • bode, bodemag, freqresp, nichols, nyquist — System response data at a vector of frequency points.

  • margin, getPeakGain, getGainCrossover, sigma — Numerical values of system response characteristics such as gain margins, phase margins, and singular values.

To obtain response plots, use:

  • bodeplot, nicholsplot, nyquistplot, sigmaplot— Plot system response data, visualize response characteristics on plots, compare responses of multiple systems on a single plot.

  • ltiview — Linear analysis tool for plotting many types of system responses simultaneously, including both time-domain and frequency-domain responses

To obtain pole-zero maps, use:

  • pzplot, iopzplot — Plot pole and zero locations in the complex plane.

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