
Saunder January 22, 2014 10:43 K15053˙Book
Linear Disturbance Estimator 37
(b)
0 0.5 1 1.5 2
–1
0
1
2
3
4
Disturbance and Estimation of d
2
Time, sec
d
2
d
2
e
d
2
Figure 2.7 (Continued) Response curves of the disturbance estimation for numer-
ical example (2.21): (a) first disturbance d
1
; (b) second disturbance d
2
.
the state information for observer design, while the frequency-domain DO only uses
the output and input information.
2.4 Extended State Observer
Consider a class of SISO uncertain systemswithorder of n, described by the following
differential equation
y
(n)
(t) = f (y (t),
˙
y(t), ... , y
(n−1)
(t), d(t), t) +bu(t), (2.25)
where d(t) the external disturbance,