An uncertain SISO nonlinear system affine in control with a mismatched exogenous disturbance input is given as follows:
x_dot = (A+delta(A)) x + B u + f(x) + D d
y=Cx
where x: states; A:system matrix, delta(A)=uncertain A matrix; B: Input matrix; f(x): nonlinear function; d: disturbance input. The disturbance input and the control inputs are at different channels (appearing in different state sapce equations).
Q/ How to design an observer for such a system?