Fig. 2. Bode plot

There are some other commands to plot frequency response. Command bode(sys) draws the Bode plot of the LTI model sys (created with either tf, zpk, ss, or frd). The frequency range and number of points are chosen automatically. bode(sys,{wmin,wmax}) draws the Bode plot for frequencies between wmin and wmax (in radians / second).

bode(sys,w) uses the user-supplied vector w of frequencies, in radian / second, at which the Bode response is to be evaluated. bode(sys1,sys2,...,w) graphs the Bode response of multiple LTI models sys1,sys2,... on a single plot. The frequency vector w is optional. You can specify a color, line style, and marker for each model, as in bode(sys1,’r’,sys2,’y--’,sys3,’gx’).

Content of the report

1.Elaboration of model, indicated by teacher.

2.Commands for calculation of frequency response and plots of frequency response.

3.Bode plots.

39

4.Results of calculation of gain and phase angle for the indicated frequency.

Control questions

1.How are transfer function and analytical expression of frequency response related?

2.What are the main ways to depict frequency response?

3.What is the physical meaning of frequency reponse magnitude and phase angle?

4.What does the Bode plot represent?

40