
Saunder January 22, 2014 10:43 K15053˙Book
48 Disturbance Observer-Based Control: Methods and Applications
Plant
Disturbance Model
∫
d
y
x
Nonlinear
Equation (3.13)
Nonlinear Disturbance Observer
u
x
.
= f (x) + g
1
(x)u + g
2
(x)d
z
.
y = h(x)
z
p(x)
C
d
ξ
ξ
•
= Aξ
d = Cξ
Figure 3.3 Block diagram of the nonlinear disturbance observer for harmonic
disturbances.
Theorem 3.1 Consider system (3.1) under the disturbances generated by exogenous
system (3.9). The enhanced harmonic disturbance observer (3.13) can exponentially
estimate the disturbances if the nonlinear observer gain l(x) is selected such that
˙
e
ξ
= [A −l(x)g
2
(x)C]e
ξ
, (3.14)
is globally exponentially stable regardless ...