Specifications

3 Operations on LTI Models
3-24
using zero-order hold on the input, and a 10 Hz sampling rate, type
h = tf(10,[1 3 10],'inputdelay',0.25);
hd = c2d(h,0.1)
This produces the discrete-time transfer function
Transfer function:
0.01187 z^2 + 0.06408 z + 0.009721
z^(–2) * ----------------------------------
z^3 – 1.655 z^2 + 0.7408 z
Sampling time: 0.1
Here the input delay in amounts to 2.5 times the sampling period of 0.1
seconds. Accordingly, the discretized model
hd inherits an input delay of two
sampling periods, as confirmed by the value of
hd.inputdelay.Theresidual
half-period delay is factored into the coefficients of
hd by the discretization
algorithm.
The step responses of the continuous and discretized models are compared in
the figure below. This plot was produced by the command
Hs
()