User`s guide

dcgain
11-57
11dcgain
Purpose Compute low frequency (DC) gain of LTI system
Syntax k = dcgain(sys)
Description k = dcgain(sys) computes the DC gain k of the LTI model sys.
Continuous Time
The continuous-time DC gain is the transfer function value a t the frequency
. For state -sp ace models with matrices , this value is
Discrete Time
The discret e -t ime DC gain is the transfer functio n va lue at . For
state-space m od e ls with m atrices , this value is
Remark T he DC g ain is i nfi n ite for systems with integrators.
Example To compute the DC gain of the MIMO transfer function
type
H = [1 tf([1 –1],[1 1 3]) ; tf(1,[1 1]) tf([1 2],[1 –3])]
dcgain(H)
ans =
1.0000 –0.3333
1.0000 –0.6667
See Also evalfr Evaluates frequency response at single frequency
norm LTIsystemnorms
s 0
=
ABCD
,,,()
KDCA
1
–
B–=
z1
=
ABCD
,,,()
KDCIA–()
1
–
B+=
Hs()
1
s 1–
s
2
s 3++
------------------------
1
s 1+
------------
s 2+
s 3–
------------
=