Networked cooperation-based distributed model predictive control using Laguerre functions for large-scale systems

International audienceThis paper proposes a novel cooperative distributed control system architecture based on unsupervised and independent Model Predictive Control (MPC) using discrete-time Laguerre functions to improve the performance of the whole system. In this distributed framework, local MPCs algorithms might exchange and require information from other sub-controllers via the communication network to achieve their task in a cooperative way. In order to reduce the computational burden in the local rolling optimization with a sufficiently large prediction horizon, the orthonormal Laguerre functions are used to approximate the predicted control trajectory. Simulation results show that the proposed architecture could guarantee satisfactory global performance even under strong interactions among the subsystems

Robusni adaptivni observer temeljen na algoritmu za kooperaciju mobilnih robota s više kotača

Wheeled mobile robots (WMRs) are of great importance. Therefore, it is necessary to make sure that they are not defected. But, in case of failures, the diagnosis task is very important to predict then solve the problem. The most useful techniques in diagnosis are observers which are based on the observability of the monitored system that is not usually ensured by WMR. Thus, to overcome this drawback, an intelligent cooperative diagnosis algorithm is proposed and tested for a group of mobile robots. The diagnosis algorithm is based on robust adaptive unknown input observer applied on unobservable robot. The local non-observability of each robot is solved by cooperative communication. The idea consists on considering all WMRs as a Large Scale System (LSS) even these robots may have not common task. Then, the LSS is decomposed into subsystems that everyone refers to each robot communicating with its neighbors. Next, a design of cooperative interconnected systems is studied to reassure the new condition of observability. Besides, Fast Adaptive Fault Estimation (FAFE) algorithm is proposed to improve the performances of the fault estimation. Finally, to illustrate the efficiency of the proposed algorithm, a model of three-wheel omnidirectional mobile robot is presented.Mobilni roboti na kotačima od velike su važnosti. Stoga, nužno je osigurati da ne odlutaju. U slučaju kvara važna je dijagnoza kako bi se predvidio i onda riješio problem. Najkorisnije dijagnostičke tehnike su observeri koji se zasnivaju na osmotrivosti nadgledanih sustava koja kod mobilnih robota na kotačima najčešće nije osigurana. Stoga, kako bi se nadišao ovaj problem, koristi se inteligentan algoritam za kooperativnu dijagnozu i testira se na grupi mobilnih robota. Dijagnostički algoritam zasniva se na robusnom adaptivnom observeru s nepoznatim ulazom koji je primijenjen na neosmotrivom robotu. Lokalna neosmotrivost svakog robota riješena je koopreativnom komunikacijom. Ideja je da se svi mobilni roboti promatraju kao sustav velikih razmjera iako roboti nemaju isti zadatak. Sustav velikih razmjera se tada rastavlja na podsutave tako da se svaki odnosi na jednog robota koji komunicira sa svojim susjedima. Zatim se proučava dizajn kooperativnih povezanih sustava kako bi se osigurali uvjeti za osmotrivost. Dodatno, predlaže se korištenje brze adaptivne estimacije pogreške kako bi se poboljšala estimacije pogreške. Konačno, prikazan je model višesmjernog mobilnog robota na tri kotača kako bi se ilustrirala učinkovitost predloženog algoritma

Contribution à la tolérance active aux défauts des systèmes dynamiques par gestion des références

The subject of this thesis is part of fault tolerant control systems under constraints with consideration of performance degradation. The main objective of this work is to consider the reference management as an integral part of the fault tolerant control system. In the literature, the most active methods of fault tolerance imply that recovery of the nominal system is always possible and that performance ratings are still achievable. This requirement is unrealistic in practice because several factors prevent the system reconfigured back to its nominal operating mode. In industry, the set of system constraints is a major problem which limits the nominal operating of the system to defined functional ranges. These functional ranges are reduced dramatically after the occurrence of some faults known as severe faults that generally affect the capacity of actuators. Therefore, this assumption of nominal performance recovery in the case of systems under constraints limits the set of faults treated with these conventional methods to a few minor faults. To remedy this problem, architecture of reconfiguration structured in two levels is proposed. The first level concerns the conventional reconfiguration algorithms acting on a reconfigurable controller, and the second acts on the module of reference management based on a reference-offset governor. The exact knowledge of the post-fault model requires a fault detection and diagnosis system to estimate the magnitude of fault, which led to the synthesis of an adaptive observer based LMI for estimating fault. To synchronize the FTC process flow, two indices have been designed. The first index refers to the decision mechanism for selecting the reconfiguration level required for the accommodation of the fault. The second index used to evaluate the level of the degradation of the system "post-fault". The performance degradation is still allowed as long as safety instructions are respected.Le sujet de cette thèse s'inscrit dans le cadre des systèmes tolérants aux défauts sous contraintes avec prise en considération de la dégradation des performances. L'objectif principal de ce travail consiste à considérer la gestion des références comme une partie intégrante du système de commande tolérant aux défauts. Dans la littérature, la plupart des méthodes actives de tolérance aux défauts supposent que le recouvrement du système nominal est toujours possible et que les performances nominales sont toujours atteignables. Cette condition est peu réaliste dans la pratique puisque plusieurs éléments empêchent le système reconfiguré de revenir à son mode de fonctionnement nominal. Dans le domaine industriel, l'ensemble des contraintes du système est un handicap majeur qui limite le fonctionnement nominal d'un système à des plages fonctionnelles bien définies. Ces plages fonctionnelles sont énormément réduites après l'apparition de certains défauts dits sévères et qui affectent généralement les actionneurs. Par conséquent, cette hypothèse de recouvrement des performances nominales dans le cas des systèmes sous contraintes limite l'ensemble des défauts traités par ces méthodes classiques à quelques défauts dits mineurs. Afin de remédier a ce problème, une architecture de reconfiguration structurée en deux niveaux est proposée. Le premier concerne les algorithmes classiques de reconfiguration en agissant sur un contrôleur reconfigurable, et le deuxième agit sur le module de gestion des références conçu à base d'un gouverneur de référence avec offset. La connaissance exacte du modèle en post-défaut nécessite un système de détection et diagnostic de défaut qui permet d'estimer l'amplitude de défaut, ce qui conduit à la synthèse d'un observateur adaptatif d'estimation de défaut à base de LMI. Afin de synchroniser le déroulement du processus FTC, deux indices ont été conçus. Le premier indice porte sur le mécanisme de décision permettant de sélectionner le/les niveau(x) de reconfiguration nécessaire(s) à l'accommodation du défaut. Le deuxième indice permet d'évaluer le niveau de dégradation du système " post-défaut ". Une dégradation de performance est toujours admise tant que les consignes de sécurité sont respectées

Energy management in WSN: IEEE 802.15.4 unslotted mode

International audienceWireless Sensor Networks suffer from many problems but energy efficient always presents the most critical trouble in this field. Many approaches and technologies were invented in order to reduce the energy consumed such as the IEEE 802.15.4. The IEEE 802.15.4 is invented for low power and Low Rate Wireless Personal Area Networks (LRWPANs). It has been updated many times in order to provide a suitable solution for this problem. It presents two different modes which are the beacon enabled mode and the non beacon enabled mode. This work is interested in the non beacon enabled mode. The paper proposes a new model to compute the energy consumed by the node in the CSMA/CA protocol specially in the unslotted algorithm. Then an auto-adaptation process is enabled. So the last quantity of energy in the battery is adapted to the activity period of the node in the network by intervening in its duty cycle in order to postpone its death. The simulation results prove both the efficiency of our consumption energy model in addition to the performance of our intervention which lead to reduce the consumed energy by node and to increase its lifetime

Industrial engineer : IE ; engineering & management solutions at work

Nowadays the energy consumption has become a critical challenge in Wireless Sensor Network (WSN). Wireless connection suffer from some weaknesse chiefly fault detection and energy efficiency which stay again the main problems in (WSN). Both was under the scope of research communities and industry engineers. We are interested to the IEEE 802.15.4 standard with beacon enabled mode. IEEE802.15.4 is a protocol designed to Physical (PHY) layer and Medium Access Control (MAC) for WSN. We intervene in the Superfame Duration (SD) which present the main private characteristic of the MAC frame in IEEE 802.15.4 in order to minimise the energy consumption when the energy level in a battery reach a critical level. IN-ETMANET/OMNeT++ simulator is used to present our method

Hidden Gaussian Markov Model for Distribued Fault Detection in Wireless Sensor Networks

International audienceWireless Sensor Networks (WSN) are based on a large number of sensor nodesused to measure informations like temperature, acceleration, displacement orpressure. The measurements are used to estimate the state of the monitoredsystem or area. However, the quality of the measurements must be guaranteedto ensure the reliability of the estimated state of the system. Actually, sensorscan be used in a hostile environment such as, on a battle field in the presence offires, floods, earthquakes, for example. In these environments as well as in normaloperation,sensors can fail.The failure of sensor nodes can also be caused by other factors like: the failure ofmodule (such as sensing module) due to the fabrication process models, batterypower losts and so on. A WSN must be able to identify faulty nodes. Thereforewe propose a probabilistic approach based on Hidden Markov Model to identifyfaulty sensor nodes. Our proposed approach predicts the future state of each nodefrom its actual state, so the fault could be detect before it occurs. We use an aidedjudgment of neighbor sensor nodes in the network. The algorithm analyses thecorrelation of the sensors’ data with respect to its neighborhood. A systematicapproach to divide a network on cliques is proposed to fully draw the neighborhoodof each node in the network. After drawing the neighborhood of each node (cliques),damaged cliques are identified using Gaussian distribution theorem. Finally, we usethe Hidden Markov model to identify faulty nodes in the identified damaged cliquesby calculating the probability of each node to stay in its normal state. Simulationresults demonstrate our algorithm is efficient even for a huge wireless sensornetwork unlike previous approaches

Integrated FDI/FTC approach for wind turbines using a LPV interval predictor subspace approach and virtual sensors/actuators

In order to keep wind turbines connected and in operation at all times despite the occurrence of some faults, advanced fault detection and accommodation schemes are required. To achieve this goal, this paper proposes to use the Linear Parameter Varying approach to design an Active Fault Tolerant Control for wind turbines. This Active Fault Tolerant Control is integrated with a Fault Detection and Isolation approach. Fault detection is based on a Linear Parameter Varying interval predictor approach while fault isolation is based on analysing the residual fault signatures. To include fault-tolerance in the control system (already available in the considered wind turbine case study based on the well known SAFEPROCESS benchmark), the information of the Fault Detection and Isolation approach block is exploited and it is used in the implementation of a virtual actuator and sensor scheme. The proposed Active Fault Tolerant Control is evaluated using fault scenarios which are proposed in the wind turbine benchmark to assess its performance. Results show the effectiveness of the proposed Active Fault Tolerant Control approach in faulty situation

RECONFIGURABLE CONTROL DESIGN WITH INTEGRATION OF A REFERENCE GOVERNOR AND RELIABILITY INDICATORS

A new approach to manage actuator redundancy in the presence of faults is proposed based on reliability indicators and a reference governor. The aim is to preserve the health of the actuators and the availability of the system both in the nominal behavior and in the presence of actuator faults. The use of reference governor control allocation is a solution to distribute the control efforts among a redundant set of actuators. In a degraded situation, a reconfigured control allocation strategy is proposed based on on-line re-estimation of the actuator reliability. A benefit of incorporating reliability indicators into over-actuated control system design is the smart management of the redundant actuators and improvement of the system safety. Moreover, when the fault is severe, an adaptation approach using the reference governor is proposed. The reference governor unit is a reference-offset governor based on a discrete-time predictive control strategy. The idea is to modify the reference according to the system constraints, which become stricter after the occurrence of an actuator fault. The proposed approach is illustrated with a flight control application

Performance evaluation based fault tolerant control with actuator saturation avoidance

In this paper, a new approach regarding a reconfigured system is proposed to improve the performance of an active fault tolerant control system. The system performance is evaluated with an intelligent index of performance. The reconfiguration mechanism is based on a model predictive controller and reference trajectory management techniques. When an actuator fault occurs in the system, a new degraded reference trajectory is generated and the controller calculates new admissible controls. A constraint set and cost function are established to avoid actuator saturation and reduce the control energy spent in closed loop dynamics. The effectiveness of the proposed method is illustrated using a hydrothermal system subject to actuator faults and constraints on actuator dynamic ranges