This thesis studies the problem of robust disturbance rejection for nonlinear systems based on three different methods: H∞ control, singular perturbation theory and multiple model adaptive control. Firstly, the disturbance suppression problem for nonlinear systems based on H∞ control is examined. We review the so-called nonstandard mixed sensitivity problem, which introduces an integrator into ...

In the future space infrastructure, the missions of refueling and capturing of the inoperative spacecraft by the orbital servicing vehicle or the space robot are considered. To achieve them, the six degrees of freedom tracking control of the chaser spacecraft is required to approach the target spacecraft. Moreover, the stability of the connected system of the chaser and target must be ensured. ...

WLAN-based location systems are implemented in indoor location service in recent years. These systems suffer largely from the signal disturbance under open WLAN environment, which introduces decrease in accuracy and stability of the location service. This paper presents a new algorithm, which utilizes multi-space projections of radio space on sub-level signal spaces to mitigate the influence fr...

We study a type of port-Hamiltonian system, in which the controller or disturbance is not applied to the flow variables, but to the systems power—a scenario that appears in many practical applications. A suitable framework is provided to model these systems and to investigate their shifted passivity properties, based on which, a stability analysis is carried out. The applicability of the result...

The paper comprises a study of absolute stability, input-to-state stability, and boundedness properties of a feedback interconnection of a finite-dimensional, linear, m-input, m-output system (A, B, C) and a set-valued nonlinearity Φ. With reference to Figure 1, we assume that D is a set-valued map in which input or disturbance signals are embedded. The analytical framework is of sufficient gen...

We address the problem of control and synchronization of a class of uncertain chaotic systems. Our approach follows techniques of sliding mode control and adaptive estimation law. The adaptive algorithm is constructed based on the sliding mode control to ensure perfect tracking and synchronization in presence of system uncertainty and external disturbance. Stability of the closed-loop system is...

A fundamental question in movement science is how humans perform stable movements in the presence of disturbances such as contact with objects. It remains unclear how the nervous system, with delayed responses to disturbances, maintains the stability of complex movements. We hypothesised that intrinsic muscle properties (i.e. the force-length-velocity properties of muscle fibres and tendon elas...

In this paper, the speed regulation problem for permanent synchronous motor (PMSM) system under vector control framework is studied. A model reference adaptive controller (MRAC) based on Lyapunov stability theory is first designed. Noticing the standard MRAC method provides a poor disturbance rejection performance in the case of strong disturbances, a composite control method which combines MRA...

In this paper, we design a tracking controller which satisfies transient response specifications and maintains tracking error within a tolerable limit for the uncertain track-following system of an optical disk drive. To this end, a robust H1 control problem with regional stability constraints and sinusoidal disturbance rejection is considered. The internal model principle is used for rejecting...

The presence of a deformable free surface in thin films driven to spread by body or shear forces gives rise to base states that are spatially nonuniform. This nonuniformity produces linearized disturbance operators that are non-normal and an eigenvalue spectrum that does not necessarily predict stability behavior. The falling film provides a simple example for demonstrating a more generalized, ...