Browsing by Author "Chen, Ying-Chun"

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    Structure-Inspired Disturbance Observer Design and Disturbance Observer-Based Control/estimation
    Chen, Ying-Chun (Virginia Tech, 2023-08-15)
    This dissertation consists of two topics: (1) structure-inspired disturbance observer design and (2) disturbance observer-based control/estimation. The disturbance is defined as the discrepancy between a model and the system the model represents. A disturbance observer is an algorithm that generates an estimate of the disturbance. The first topic illustrates a disturbance observer that provides a big class of nonlinear systems with a large basin of attraction, even ensuring global convergence. Such robustness is achieved by leveraging particular system nonlinearities in the observer design. The second topic discusses the usage of disturbance estimates to counteract or capture the effects of disturbances to recover the nominal controller/estimator performance. The main research results are theorems concerning stability analysis of the disturbance observer and the disturbance observer-based systems, whose practical aspects are supported by three application examples---a fixed-wing aircraft, an underwater vehicle, and a Furuta pendulum.
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    A Structure-Inspired Disturbance Observer for Finite-Dimensional Mechanical Systems
    Chen, Ying-Chun; Woolsey, Craig A. (IEEE, 2024-03)
    This article describes a disturbance observer (DO) design for systems whose dynamics are piecewise differentiable and satisfy certain structural conditions. Provided a Lipschitz continuity condition holds with a sufficiently small Lipschitz constant—a condition that is implied by “sufficiently slow” dynamics—the observer ensures local ultimate boundedness of the disturbance estimate error, which converges exponentially to a positively invariant set whose size can be made arbitrarily small. This observer is appropriate for finite-dimensional mechanical systems. We demonstrate the design in two examples—a tutorial example of a nonlinear mass-damper-spring system and a practical example of an experimental underwater vehicle.