In disturbance-observer-based control, the closed loop system consists of a main feedback control loop and an inner disturbance observer loop. This paper presents a design method for a disturbance observer to satisfy closed loop performance specifications, provided that the main feedback controller is known. Taking advantage of certain fixedstructure disturbance observers, the disturbance obser...

In this paper, we build bounded error observers for a common class of partially known bioreactor models. The main idea is to construct hybrid bounded observers "between" high gain observer, which has an adjustable convergence rate but requires perfect knowledge of the model, and asymptotic observer which is very robust towards uncertainty but has a fixed convergence rate. An hybrid bounded erro...

Despite providing robustness, high-gain observers impose a peaking phenomenon, which may cause instability, on the system states. In this paper, an adaptive saturation is proposed to attenuate the undesirable mentioned phenomenon in high-gain observers. A real-valued and differentiable sigmoid function is considered as the saturating element whose parameters (height and slope) are adaptively tu...

An adaptive output feedback is presented. The adaptive gain is used to relax the restriction of knowing the perturbation bound. it is proved that with the adaptive gain both, the controller and the observer converge to the origin. A Lyapunov approach is used to proved the results and give restrictions on the fixed gains of the controller and the observer.

This paper proposes a relatively simple adaptive controller for systems with higher relative degree. Only little information on the system is needed: only the relative degree and a lower bound on the positive high-frequency gain. The zero-dynamics does not need to be asymptotically stable, boundedness is sufficient. The controller achieves λ-tracking for a large class of nonlinear systems and c...

The robust L2-gain estimation is investigated for general uncertain systems with structured uncertainties. A new estimation structure is introduced: the Augmented-Gain Observer which encompasses both filters and observers and allows robust estimation even for some classes of unstable systems. Our approach is based on a separation of graphs theorem using frequency dependent Integral Quadratic Co...

The problem of High-Gain Observer Design is addressed for a class 3 × inhomogeneous linear hyperbolic systems with possibly distinct characteristic velocities and considering distributed measurement part the state. Applying an infinite-dimensional state transformation, system mapped into new set partial differential equations, satisfying appropriate form observer design. includes output correct...