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The paper consider some special topics related to controllability of linear switching systems. Consequences of the normal controllability property and controllability under sampling are investigated. Both problems are related to the existence of a finite switching sequence with certain properties. It is shown that completely controllable linear switching systems, regardless to the sign of the allowed...
The method of sample-based minimax optimization is developed for the minimization problem with an uncertain quadratic objective function subject to linear constraints. Several examples based on confidence statistical estimation are considered to define the uncertainty set. Analytical and numerical techniques are proposed for finding the optimal robust strategy.
In this paper a recursive technique, based on the subspace state space identification methods, is presented for identification of time-varying systems. The main idea was to develop an iterative algorithm with most of the advantages of this kind of methods in order to deal with real-time applications and minimize the computational burden. As a subspace-based state space system identification technique,...
In this paper wo prosont a now methodology, based on dynamic inversion, for the set-point constrained regulation of a scalar linear system with structured uncertainties. The approach basically relies on the combined design of the controller and of the reference command input. The first is based on LQR methodology whilst the latter is determined by means of a stable dynamic inversion. An illustrative...
New algorithms are presented for the computation of good upper and lower bounds on the structured singular value μ, for high order plants subject to purely real or mixed real/complex uncertainty. A geometric form of the Hahn-Banach theorem is used to develop an algorithm for computing an upper bound on μ, involving a linear program and a symmetric eigenvalue problem at each iteration. A proof of convergence...
A fault isolation observer is developed for failure detection and isolation of multiple faults in discrete-time dynamic systems. The design of freedom remaining available after directional residuals generation is used to satisfy an H ∞ disturbance attenuation constraint.
An architecture for fault tolerant feedback controllers based on the Youla parameterization is suggested. It is shown that the Youla parameterization will give a residual vector directly in connection with the fault diagnosis part of the fault tolerant feedback controller. It turns out that there is a separation between the feedback controller and the fault tolerant part. The closed loop feedback...
Adaptive filters with suitable nonlinear devices are very effective in suppressing the adverse effect due to impulse noise. In a previous work, the authors have proposed a new class of nonlinear adaptive filters using the concept of robust statistics [1,2]. The robust M-estimator is used as the objective function, instead of the mean square errors, to suppress the impulse noise. The optimal coefficient...
In this note we extend the design tool presented in [6] for robust stabilization of nonminimum-phase nonlinear systems to the case of output regulation problems. As in [6] we take advantage from a design tool known in the linear literature as “vibrational feedback” to handle the presence of unstable zero dynamics in output regulation problems in presence of uncertainties. This work frames in a research...
This paper proposes an original solution for the observation of nonlinear uncertain systems. Features of this observer based on high order sliding modes are a finite and a priori known convergence time, robustness against unstructured (even unmatched) uncertainties and limited chattering. This is, as far as the authors known, the first observer structure which garantees an a priori known convergence...
A fast and robust algorithm for the separation of complex valued signals is presented. It is assumed that the original, complex valued source signals are mutually statistically independent, and that the mixing process is linear. The problem is solved by the independent component analysis (ICA) model. ICA is a statistical method for transforming an observed multidimensional random vector into components...
In this paper we present a new control approach based on both: Linear Matrix Inequalities and Sliding Mode Control. This strategy is applied to interconnected systems which consider local disturbances (matched and unmatched disturbances) together with local and remote uncertainties. The proposed approach guarantees global stability by using only an output feedback. The control law is composed by two...
In this paper, adaptive threshold generation for robust fault detection is analyzed. Uncertainties due to parameter variations are considered in the system model using an interval model. An interval observer is used as a suitable passive robust strategy to generate an adaptive threshold by propagating uncertainty to the residuals. The design procedure of this observer is implemented via pole placement...
In this paper, we address the problem of robust moving horizon observer for nonlinear discrete-time systems. The main contribution lies in the use of a robust moving horizon approach in a Luenberger structure observer. Thanks to this new design, a new nonrestrictive synthesis condition, expressed in term of Bilinear Matrix Inequality (BMI), is obtained. Indeed, the obtained BMI contains more degree...
This paper develops a design approach, based on sampled data robust feedback H∞-control, for stabilisation of the upright posture of paraplegic persons standing. The subject stands in a special apparatus which braces the knee and hip joints. Stabilising torque at the ankle joint is produced by electrical stimulation of the paralyzed calf muscle of both legs using surface electrodes. The goal in this...
This paper considers robust control with a stable controller using proportional-integral-plus control techniques. A formulation of robust PIP controllers is proposed on the basis of parametric pole assignment. The robustness function in the frequency domain is minimised using the freedom provided by parametric pole assignment. It shows how to combine time-domain performance specifications provided...
In this paper, we use sliding mode control theory to design a 3D vision based controller that is robust to bounded parametric estimation errors. First, we give a model of an eye-in-hand 6 DOF robotic system, including the Pose Reconstruction Algorithm (PRA) used to estimate the position and orientation of the camera with respcet to the scene. In a second step, we propose a model for the uncertainties...
This paper deals with the so-called robust disturbance attenuation problem. This problem is to find the controller which robustly minimizes the infinity norm of the weighted sensitivity function. So this is a robust performance problem. This problem has not been solved at an analytical level. However, one can try to approach the optimum using, for instance, μ-synthesis or the convex optimization paradigm...
A vector-valued impulsive control problem is considered whose dynamics, defined by a differential inclusion, have to satisfy state constraints and are such that the vector fields associated with the singular term do not satisfy the so called Frobenius condition. A concept of robust solution based on a new reparametrization procedure is adopted in order to derive necessary conditions of optimality...
A general question one has to face in the study of an optimal control problem is the representation of the closure of the set of trajectories. Loosely speaking, two main problems lie at the basis of the non triviality of this question: the lack of sufficient convexity assumptions (which is at the origin of the introduction of the so-called chattering controls) and the occurrence of unbounded controls...
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