Appreciation of transient behaviour of nonlinear states observers from their applications

The paper presents some results about the transient behavior of high gain observer (HGO) represented the class of nonlinear asymptotic observers, and the observer introduced by Shen and Xia [1], represented the class of nonlinear finite time observer (FTO), which are obtained from their applications in robot control. The received results will support to decide a suitable method for designing of nonlinear output feedback controller based on separation principle. In particular the obtained results also show that as different as linear systems, in nonlinear systems the error overshoot and the transient time are not totally opposite to each other.