National Instruments 370753C-01 Manual De Usuario
Chapter 1
Introduction
© National Instruments Corporation
1-19
You can use the default exponential discretization method with
dt
= 0.01
and compare frequency responses between the original system and the
discretized system:
discretized system:
ssysd = discretize(ssys, 0.01);
f = freq(ssys,logspace(.001,10,200));
fd = freq(ssysd,logspace(.001,10,200));
In the following statements you compute the gain and phase of both
systems and then plot them.
systems and then plot them.
db = 20*log10(abs(f)); ph = (180/pi)*atan2(f);
dbd = 20*log10(abs(fd)); phd = (180/pi)*atan2(fd);
plot([db;ph;dbd;phd],{strip=2,xlog,
ylab = ["Gain (dB)";"Phase (deg)"],
x_lab = "Frequency (Hz)",
legend = ["ssys";"ssysd"]})
In Figure 1-11 you can see the frequency responses match closely,
indicating that this discretization method captures the continuous system’s
dynamics accurately.
indicating that this discretization method captures the continuous system’s
dynamics accurately.
Figure 1-11. Frequency Response of ssys and Its Discrete Equivalent ssysd