Stabilization of nonlinear systems in presence of filtered output via extended high-gain observers

International audienceWe consider the problem of stabilizing a nonlinear system with filtered output. Given an output feedback control law which satisfies a stability requirement, we consider the case in which the necessary output cannot be measured. The measure is rather the output of an auxiliary stable dynamics in cascade with the system. In place of fully redesign the control architecture, we slightly modify the original control law design by adding a disturbance observer and we recover the desired stability property for the system. The disturbance observer is design as an extended high-gain observer

Application of a Fault Detection and Isolation System on a Rotary Machine

The paper illustrates the design and the implementation of a Fault Detection and Isolation (FDI) system to a rotary machine like a multishaft centrifugal compressor. A model-free approach, that is, the Principal Component Analysis (PCA), has been employed to solve the fault detection issue. For the fault isolation purpose structured residuals have been adopted while an adaptive threshold has been designed in order to detect and to isolate the faults. To prove the goodness of the proposed FDI system, historical data of a nitrogen centrifugal compressor employed in a refinery plant are considered. Tests results show that detection and isolation of single as well as multiple faults are successfully achieved

Multi-pattern output consensus in networks of heterogeneous nonlinear agents with uncertain leader: a nonlinear regression approach

International audienceIn this paper we consider the problem of consensus of a network of heterogeneous nonlinear agents on a family of different desired trajectories generated by an uncertain leader. We design a set of local reference generators and local controllers which guarantees that the agents achieve consensus robustly on all possible trajectories inside this family. The design of the local reference generators is based on the possibility to express the trajectory of the leader as a nonlinear regression law which is parametrized by some constant unknown parameters

Emulation-based semiglobal output regulation of minimum phase nonlinear systems with sampled measurements

International audienceWe investigate the semiglobal output regulation of minimum-phase single-input single-output nonlinear systems with sampled measurements. We proceed by emulation. We start by considering a continuous-time regulator, which solves the problem in the absence of sampling. Then, we consider sampled measurements and we model the overall system as a hybrid system. We show that the original continuous-case properties are preserved when the measurements are sampled provided that the maximum allowable transmission interval satisfies a given explicit bound

Data-based design of fault detection and isolation (FDI) systems

Lo scopo di questa tesi è la presentazione di un innovativo sistema di Fault Detection e Isolation (FDI) basato su un approccio data-driven. La scelta di utilizzare un approccio data-based è stata dettata dal fatto che, molto spesso, in applicazioni industriali, modelli dinamici del processo non sono disponibili o non sono particolarmente utili per scopi diagnostici. L’innovativo sistema FDI proposto combina le seguenti metodologie: Principal Component Analysis (PCA), Cluster Analysis e Pattern Recognition. Il risultato è quello che l’autore ha definito Fuzzy Fault Classifier (FFC). La combinazione delle tre tecniche sopracitate permette di rilevare ed isolare automaticamente guasti singoli e guasti multipli. Questo sistema è stato altresì arricchito dall’uso di soglie adattative la cui progettazione si è inspirata a degli schemi classici proposti in letteratura; l’apporto innovativo è stato quello di identificare alcuni parametri incogniti attraverso un approccio basato sull’uso dell’analisi spettrale dei segnali di ingresso. Per risolvere il cruciale problema della scelta delle Componenti Principali nella PCA, è stato presentato un nuovo metodo basato sul noto test statistico ANOVA (ANalysis Of VAriance); tale metodologia è stata confrontata con altri approcci ed i suoi benefici possono essere valutati. Il sistema FDI descritto è stato testato per valutare le capacità di identificazione e di isolamento dei guasti singoli e multipli, assieme ai principali gusti di processo, dei seguenti processi reali: Compressore Centrifugo Multistadio e Unmanned Surface Vehicle (USV). La bontà e l'efficienza del sistema FDI possono essere apprezzate valutando i risultati ottenuti. Essi confermano la capacità del sistema in termini di individuazione ed isolamento dei guasti ed inoltre, vista la sua caratteristica data-based, la possibilità di estenderne l'uso ad altri processi. L'unico requisito è la presenza di misure affidabili delle principali grandezze di processo

Emulation-based semiglobal output regulation of minimum phase nonlinear systems with sampled measurements

International audienceWe investigate the semiglobal output regulation of minimum-phase single-input single-output nonlinear systems with sampled measurements. We proceed by emulation. We start by considering a continuous-time regulator, which solves the problem in the absence of sampling. Then, we consider sampled measurements and we model the overall system as a hybrid system. We show that the original continuous-case properties are preserved when the measurements are sampled provided that the maximum allowable transmission interval satisfies a given explicit bound

Multilegged Underwater Running With Articulated Legs

Drawing inspiration from the locomotion modalities of animals, legged robots demonstrated the potential to traverse irregular and unstructured environments. Successful approaches exploited single-leg templates, like the spring-loaded inverted pendulum (SLIP), as a reference for the control of multilegged machines. Nevertheless, the anchoring between the low-order model and the actual multilegged structure is still an open challenge. This article proposes a novel strategy to derive actuation inputs for a multilegged robot by expressing the control requirements in terms of jump height and forward speed (derived from the limit cycle). We found that these requirements could be associated with a specific maximum force, successively split on an arbitrary number of legs and their relative actuation sets. The proposed approach has been validated in multibody simulation and real-world experiments by employing the underwater hexapod robot SILVER2. Results show that locomotion performances of the low-order model are reflected by the simulated and actual robot, showing that the articulated-USLIP (a-USLIP) model can faithfully explain the multilegged behavior under the imposed control inputs once hydrodynamic parameters have been tuned. More importantly, the proposed controller can be translated to the terrestrial case with minimal modifications and extended with additional layers to obtain more complex behaviors

Application of a Mahalanobis-Based Pattern Recognition Technique for Fault Diagnosis on a Chemical Process

In the paper a Fault Detection and Isolation (FDI) procedure based on a model-free approach and the use of pattern recognition techniques is described. The presented results refer to its implementation on a Air Separation Unit (ASU) of a refinement plant and show the goodness of the overall procedure in the detections of single as well as multiple faults and its promptness in terms of faults isolatio

Emulation-based semiglobal output regulation of minimum phase nonlinear systems with sampled measurements

International audienceWe investigate the semiglobal output regulation of minimum-phase single-input single-output nonlinear systems with sampled measurements. We proceed by emulation. We start by considering a continuous-time regulator, which solves the problem in the absence of sampling. Then, we consider sampled measurements and we model the overall system as a hybrid system. We show that the original continuous-case properties are preserved when the measurements are sampled provided that the maximum allowable transmission interval satisfies a given explicit bound