Reference : Adaptive high-gain extended kalman filter and applications
 Document type : Dissertations and theses : Doctoral thesis Discipline(s) : Engineering, computing & technology : Multidisciplinary, general & others To cite this reference: http://hdl.handle.net/10993/15672
 Title : Adaptive high-gain extended kalman filter and applications Language : English Author, co-author : Boizot, Nicolas [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Computer Science and Communications Research Unit (CSC)] Publication date : 30-Apr-2010 Institution : University of Luxembourg, ​Luxembourg, ​​Luxembourg Université de Bourgogne, ​​France Name of the degree : Docteur en Informatique Supervisor : Sachau, Jürgen Busvelle, Eric Keywords : [en] nonlinear observers ; nonlinear systems ; extended Kalman filter ; adaptive high-gain observer ; continuous-discrete observer ; DC-motor ; real-time implementation Abstract : [en] The work concerns the observability problem” --- the reconstruction of a dynamic process's full state from a partially measured state--- for nonlinear dynamic systems. The Extended Kalman Filter (EKF) is a widely-used observer for such nonlinear systems. However it suffers from a lack of theoretical justifications and displays poor performance when the estimated state is far from the real state, e.g. due to large perturbations, a poor initial state estimate, etc… We propose a solution to these problems, the Adaptive High-Gain (EKF). Observability theory reveals the existence of special representations characterizing nonlinear systems having the observability property. Such representations are called observability normal forms. A EKF variant based on the usage of a single scalar parameter, combined with an observability normal form, leads to an observer, the High-Gain EKF, with improved performance when the estimated state is far from the actual state. Its convergence for any initial estimated state is proven. Unfortunately, and contrary to the EKF, this latter observer is very sensitive to measurement noise. Our observer combines the behaviors of the EKF and of the high-gain EKF. Our aim is to take advantage of both efficiency with respect to noise smoothing and reactivity to large estimation errors. In order to achieve this, the parameter that is the heart of the high-gain technique is made adaptive. \textit{Voila}, the Adaptive High-Gain EKF. A measure of the quality of the estimation is needed in order to drive the adaptation. We propose such an index and prove the relevance of its usage. We provide a proof of convergence for the resulting observer, and the final algorithm is demonstrated via both simulations and a real-time implementation. Finally, extensions to multiple output and to continuous-discrete systems are given. Permalink : http://hdl.handle.net/10993/15672

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