creating discrete-凯发k8网页登录

specifying discrete-time models

control system toolbox™ lets you create both continuous-time and discrete-time models. the syntax for creating discrete-time models is similar to that for continuous-time models, except that you must also provide a sample time (sampling interval in seconds).

for example, to specify the discrete-time transfer function:

with sampling period ts = 0.1 s, type:

num = [ 1  -1 ];
den = [ 1  -1.85  0.9 ];
h = tf(num,den,0.1)

h =
 
        z - 1
  ------------------
  z^2 - 1.85 z   0.9
 
sample time: 0.1 seconds
discrete-time transfer function.

or equivalently:

z = tf('z',0.1);
h = (z - 1) / (z^2 - 1.85*z   0.9);

similarly, to specify the discrete-time state-space model:

with sampling period ts = 0.1 s, type:

sys = ss(.5,1,.2,0,0.1);

recognizing discrete-time systems

there are several ways to determine if your lti model is discrete:

for example, for the transfer function h specified above,

h.ts

ans = 0.1000

isdt(h)

ans = logical
   1

you can also spot discrete-time systems by looking for the following traits:

the following plots show these characteristic traits:

step(h)

bode(h), grid