1,720,964 research outputs found
TRAPEZOIDAL RULE FOR NUMERICAL EVALUATION OF FRACTIONAL ORDER INTEGRALS WITH APPLICATIONS TO SIMULATION AND IDENTIFICATION OF FRACTIONAL ORDER SYSTEMS
No full textThis paper presents an extension of the well-known trapezoidal (bilinear) integration rule, that in the present work is applied to the numerical evaluation of fractional-order integrals. Particularly, this approximation is exploited to derive viable numerical algorithms addressing two distinct problems: i) simulation of Linear Time-Invariant (LTI) Commensurate Fractional Order Systems (CFOS); ii) non-recursive parameter estimation in LTI-CFOS. More precisely, the problem of non-recursive parameter estimation is addressed in two different scenarios. The first one is when the commensurate order of the CFOS is known in advance, while the second, more general, one is that in which the commensurate order is unknown and is to be estimated. The effectiveness of the proposed methods is illustrated by numerical examples
Second-order sliding mode approaches to disturbance estimation and fault detection in fractional-order systems
No full textThis paper outlines some results concerning the application of second-order sliding-mode techniques to address estimation and fault detection problems involving fractional order (FO) dynamics. Perturbed and switched FO systems are dealt with throughout the paper. Simple tuning formulas for the suggested schemes are constructively developed along the paper by means of appropriate Lyapunov analysis. Simulation and experimental results confirm the expected performance
Adaptive unit-vector law with time-varying gain for finite-time parameter estimation in LTI systems
No full textA continuation of previous authors' work on adaptive parameter estimation for linear dynamical systems having irrational transfer function is presented in this work. An original modification of the gradient algorithm, inspired by the variable structure control techniques and additionally featuring a time-varying adaptation gain, is presented and analyzed using Lyapunov techniques. The exposition is illustrated by several numerical examples which illustrate the effectiveness of the proposed algorithm
Nonlinear Discrete-Time Algorithm for Fractional Derivatives Computation with Application to PI^\lambda D^μ Controller Implementation
No full textThis paper presents a novel algorithm for the numerical computation of fractional-order derivatives, based on a suitable generalization of a sliding-mode based robust and exact first-order differentiator (see Levant (1998)). The method inherits the robustness properties against the measurement noise of the original scheme. The algorithm is first devised in the continuous time setting, leading to a block scheme where conventional and fractional order integrators are suitably combined in a closed loop configuration containing certain "stabilizing" static non-linearities as well. All integrators are discretized by an algorithm of the Adams-Bashforth-Moulton type (cfr. Diethelm et al, (2004)) yielding an overall discrete time form of the proposed fractional differentiator. The algorithm is then applied to derive a discretized implementation formula for the PIλDμ controller. Simulation and experimental tests are carried out to verify the performance of the proposed algorithm and to compare it with other existing approaches
Adaptive identification of the commensurate order in fractional processes by means of variable-order operators
No full textA gradient-based algorithm for the on-line continuous estimation of the commensurate order in linear fractional order processes is presented. A key aspect of the proposed methodology is the use of appropriate variable-order fractional filters, and linear Laplace operators of logarithmic type, within the estimation mechanism. A Lyapunov based analysis will be provided for deriving appropriate sufficient conditions guaranteeing the parameter convergence property. Realization issues associated to the involved variable order operators are discussed, and a fully developed analysis and design example, accompanied by relevant simulation results, is provided to support the presented theory
ON-LINE ADAPTIVE CLUSTERING FOR PROCESS MONITORING AND FAULT DETECTION
No full textAn adaptive clustering procedure specifically designed for process monitoring, fault detection and isolation is presented in this paper. The key feature of the proposed procedure can be identified as its underlying capability to detect novelties in the system's mode of operation and, thus, to identify previously unseen functioning modes of the process. Once a novelty is detected, relevant informations are used to enrich the knowledge-base of the algorithm and as a result the proposed clustering procedure evolves and learns the new features of the monitored process in accordance with the available process data. The suggested clustering procedure is theoretically illustrated and its effectiveness has been investigated experimentally. Particularly, the on-line implementation of the algorithm and its integration with a fault detection expert system have been considered by making reference to a pneumatic process
Adaptive parameter estimation for infinite-dimensional LTI systems with finite-time convergence
No full textA novel adaptive algorithm to address the on-line identification of constant uncertain parameters in linear timeinvariant dynamical systems is proposed. The approach can be applied to a broad class of linear dynamical processes including, e.g., delay systems, fractional-order systems, and distributedparameter systems. The proposed scheme takes advantage of a nonlinear adaptation rule inspired by the unit-vector variable-structure control strategy and provides the finite-time parameter estimation. Convergence properties of the algorithm are investigated through Lyapunov analysis, that constructively yields explicit convergence conditions which generalize the wellknown Persistence of Excitation (P.E.) and identifiability requirements arising in conventional adaptive estimation. The theoretical findings are substantiated by extensive simulation examples
Second-order sliding modes and soft computing techniques for fault detection
No full textThis paper outlines some results concerning the combined application of secondorder
sliding-mode and soft-computing techniques in the framework of fault-detection problems.
A method for estimating the discrete state of an LTI affine switched system is developed to that
end. Simple controller/observer tuning formulas are constructively developed along the paper
by Lyapunov analysis. Simulation and experimental results confirm the expected performance
- …
