Output derivative estimation and disturbance attenuation using PI observer with application to a class of nonlinear systems

High-gain observers have been used to estimate derivatives of the output in different applications. These observers have shown great advantages in the design of nonlinear output feedback control of nonlinear systems. However, when disturbances and/or noises are present in the systems, the performance of high-gain observers is degraded. We try to overcome this deficiency by investigating the applicability of proportional integral (PI) observers. A PI observer has successfully been used in LTR design and it has shown the ability of simultaneous estimation of states and disturbances. This paper proposes a new output derivative estimation using a PI observer for certain classes of nonlinear systems. Simulation results demonstrate the robustness of PI observers.