125 research outputs found

    On designing observers for time-delay systems with nonlinear disturbances

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    This is the post print version of the article. The official published version can be obtained from the link below - Copyright 2002 Taylor & Francis LtdIn this paper, the observer design problem is studied for a class of time-delay nonlinear systems. The system under consideration is subject to delayed state and non-linear disturbances. The time-delay is allowed to be time-varying, and the non-linearities are assumed to satisfy global Lipschitz conditions. The problem addressed is the design of state observers such that, for the admissible time-delay as well as non-linear disturbances, the dynamics of the observation error is globally exponentially stable. An effective algebraic matrix inequality approach is developed to solve the non-linear observer design problem. Specifically, some conditions for the existence of the desired observers are derived, and an explicit expression of desired observers is given in terms of some free parameters. A simulation example is included to illustrate the practical applicability of the proposed theory.The work of Z. Wang was supported in part by the University of Kaiserslautern of Germany and the Alexander von Humboldt Foundation of Germany

    Robust control of microvibrations with experimental verification

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    The paper addresses the problem of actively attenuating a particular class of vibrations, known as microvibrations, which arise, for example, in panels used on satellites. A control scheme which incorporates feedback action is developed which operates at a set of dominant frequencies in a disturbance spectrum, where the control path model is estimated online. Relative to earlier published techniques, a new feature of the presented controller is the use of the inverse Hessian to improve adaptation speed. The control scheme also incorporates a frequency estimation technique to determine the relevant disturbance frequencies with higher precision than the standard fast Fourier transform (FFT). The control scheme is implemented on an experimental test-bed and the total achieved attenuation, as measured from the experiments, is 26dB. The low computational demand of the control scheme allows for single chip controller implementation, a feature which is particularly attractive for potential applications areas, such as small satellites, where there are critical overall weight restrictions to be satisfied whilst delivering high quality overall performance

    Tracking performance of ‘nn’ integral-plus-time constant plants with 'one' controller

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