Nonlinear High Gain Observer in Feedback Control System

In context to feedback control system, the problem of state estimation for a class of nonlinear systems with measurement noise is studied. It is well understood that when implemented in feedback loop, the high gain observers are sensitive to measurement noise but are robust to model uncertainity. A trade-off always exists between fast state reconstruction and attenuation of measurement noise. A nonlinear gain approach can be used to overcome this trade-off between fast state reconstruction and measurement noise attenuation. In presence of measurement noise, the estimation error can be noticeably compromised if the observer gain is chosen too large. To achieve this, a high gain of the observer is used in transient state and lower gain is generated when steady state is reached. The effect of noise on the steady state performance is reduced by reducing the observer gain after achieving satisfactory state estimates.