Recent advances on filtering and control for nonlinear stochastic complex systems with incomplete information: A survey

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2012 Hindawi PublishingSome recent advances on the filtering and control problems for nonlinear stochastic complex systems with incomplete information are surveyed. The incomplete information under consideration mainly includes missing measurements, randomly varying sensor delays, signal quantization, sensor saturations, and signal sampling. With such incomplete information, the developments on various filtering and control issues are reviewed in great detail. In particular, the addressed nonlinear stochastic complex systems are so comprehensive that they include conventional nonlinear stochastic systems, different kinds of complex networks, and a large class of sensor networks. The corresponding filtering and control technologies for such nonlinear stochastic complex systems are then discussed. Subsequently, some latest results on the filtering and control problems for the complex systems with incomplete information are given. Finally, conclusions are drawn and several possible future research directions are pointed out.This work was supported in part by the National Natural Science Foundation of China under Grant nos. 61134009, 61104125, 61028008, 61174136, 60974030, and 61074129, the Qing Lan Project of Jiangsu Province of China, the Project sponsored by SRF for ROCS of SEM of China, the Engineering and Physical Sciences Research Council EPSRC of the UK under Grant GR/S27658/01, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany

Fault detection and isolation in a networked multi-vehicle unmanned system

Recent years have witnessed a strong interest and intensive research activities in the area of networks of autonomous unmanned vehicles such as spacecraft formation flight, unmanned aerial vehicles, autonomous underwater vehicles, automated highway systems and multiple mobile robots. The envisaged networked architecture can provide surpassing performance capabilities and enhanced reliability; however, it requires extending the traditional theories of control, estimation and Fault Detection and Isolation (FDI). One of the many challenges for these systems is development of autonomous cooperative control which can maintain the group behavior and mission performance in the presence of undesirable events such as failures in the vehicles. In order to achieve this goal, the team should have the capability to detect and isolate vehicles faults and reconfigure the cooperative control algorithms to compensate for them. This dissertation deals with the design and development of fault detection and isolation algorithms for a network of unmanned vehicles. Addressing this problem is the main step towards the design of autonomous fault tolerant cooperative control of network of unmanned systems. We first formulate the FDI problem by considering ideal communication channels among the vehicles and solve this problem corresponding to three different architectures, namely centralized, decentralized, and semi-decentralized. The necessary and sufficient solvability conditions for each architecture are also derived based on geometric FDI approach. The effects of large environmental disturbances are subsequently taken into account in the design of FDI algorithms and robust hybrid FDI schemes for both linear and nonlinear systems are developed. Our proposed robust FDI algorithms are applied to a network of unmanned vehicles as well as Almost-Lighter-Than-Air-Vehicle (ALTAV). The effects of communication channels on fault detection and isolation performance are then investigated. A packet erasure channel model is considered for incorporating stochastic packet dropout of communication channels. Combining vehicle dynamics and communication links yields a discrete-time Markovian Jump System (MJS) mathematical model representation. This motivates development of a geometric FDI framework for both discrete-time and continuous-time Markovian jump systems. Our proposed FDI algorithm is then applied to a formation flight of satellites and a Vertical Take-Off and Landing (VTOL) helicopter problem. Finally, we investigate the problem of fault detection and isolation for time-delay systems as well as linear impulsive systems. The main motivation behind considering these two problems is that our developed geometric framework for Markovian jump systems can readily be applied to other class of systems. Broad classes of time-delay systems, namely, retarded, neutral, distributed and stochastic time-delay systems are investigated in this dissertation and a robust FDI algorithm is developed for each class of these systems. Moreover, it is shown that our proposed FDI algorithms for retarded and stochastic time-delay systems can potentially be applied in an integrated design of FDI/controller for a network of unmanned vehicles. Necessary and sufficient conditions for solvability of the fundamental problem of residual generation for linear impulsive systems are derived to conclude this dissertation

Discrete Time Systems

Discrete-Time Systems comprehend an important and broad research field. The consolidation of digital-based computational means in the present, pushes a technological tool into the field with a tremendous impact in areas like Control, Signal Processing, Communications, System Modelling and related Applications. This book attempts to give a scope in the wide area of Discrete-Time Systems. Their contents are grouped conveniently in sections according to significant areas, namely Filtering, Fixed and Adaptive Control Systems, Stability Problems and Miscellaneous Applications. We think that the contribution of the book enlarges the field of the Discrete-Time Systems with signification in the present state-of-the-art. Despite the vertiginous advance in the field, we also believe that the topics described here allow us also to look through some main tendencies in the next years in the research area

Nonlinear Systems

Open Mathematics is a challenging notion for theoretical modeling, technical analysis, and numerical simulation in physics and mathematics, as well as in many other fields, as highly correlated nonlinear phenomena, evolving over a large range of time scales and length scales, control the underlying systems and processes in their spatiotemporal evolution. Indeed, available data, be they physical, biological, or financial, and technologically complex systems and stochastic systems, such as mechanical or electronic devices, can be managed from the same conceptual approach, both analytically and through computer simulation, using effective nonlinear dynamics methods. The aim of this Special Issue is to highlight papers that show the dynamics, control, optimization and applications of nonlinear systems. This has recently become an increasingly popular subject, with impressive growth concerning applications in engineering, economics, biology, and medicine, and can be considered a veritable contribution to the literature. Original papers relating to the objective presented above are especially welcome subjects. Potential topics include, but are not limited to: Stability analysis of discrete and continuous dynamical systems; Nonlinear dynamics in biological complex systems; Stability and stabilization of stochastic systems; Mathematical models in statistics and probability; Synchronization of oscillators and chaotic systems; Optimization methods of complex systems; Reliability modeling and system optimization; Computation and control over networked systems

Design methods for networked control systems with unreliable channels focusing on packet dropouts

Texto completo descargado en TeseoLos sistemas de control a través de redes se han convertido en un área importante dentro de la comunidad de control, lo cual es debido a su bajo coste y a la flexibilidad de sus aplicaciones. Los sistemas de control a través de redes (NCSs) se componen de sensores, actuadores y controladores; las operaciones entre ellos se coordinan a través de una red de comunicación. Típicamente, estos sistemas están espacialmente distribuidos, y pueden funcionar de manera asíncrona, pero sus operaciones han de estar coordinadas para conseguir los objetivos deseados. En este resumen se presenta una perspectiva general de los NCSs, y en particular, los casos específicos en los que se ha basado esta tesis, abordando los temas principales relacionados con NCS, con todos los problemas y ventajas asociados, se describen en este resumen. Por último, se presenta un índice de la tesis con sus contribuciones más relevantes. - Introducción a los Sistemas de Control a través de Red Los Sistemas de Control a través de Red (NCSs) son sistemas espacialmente distribuidos donde la comunicación entre plantas, sensores, actuadores y controladores se realiza a través de una red de comunicación. La complejidad en el diseño y la realización, el coste del cableado, la instalación y el mantenimiento pueden ser reducidos drásticamente incluyendo una red de comunicación. Sin embargo, las redes de comunicación en los sistemas también traen algunos incovenientes como los retrasos y la pérdida de datos, los errores de codificación, etc. Estos incovenientes pueden ser la causa de la de la degradación del comportamiento del sistema e incluso causar su desestabilización. Hoy en día, hay un gran número de situaciones prácticas en las que el uso de redes de comunicación para el control son necesarias para aplicaciones o procesos de control en ingeniería. Algunos ejemplos son: Situaciones en las que el espacio y el peso están limitados. Situaciones en las que las distancias a considerar son grandes. Aplicaciones de control donde el cableado no es posible. El uso de redes de comunicación digitales proporciona también algunas ventajas: La complejidad en el cableado en conexiones punto a punto se reduce mucho, así como el coste. Además, los costes de instalación pueden reducirse también drásticamente. La reducción en la complejidad del cableado hace mucho más fácil el diagnóstico y el mantenimiento del sistema, dando lugar a un ahorro en el coste debido a que la instalación y el funcionamiento tienen una eficiencia mayor. Los NCSs son flexibles y reconfigurables. Fiabilidad, redundancia y robustez ante los fallos. Los NCSs proporcionan modularidad, control descentralizado y diagnósticos integrados. Todas estas ventajas sugieren que los NCSs jugarán un papel principal en un futuro cercano, siendo un área de investigación muy prometedora. - Objetivos de la tesis La idea general de esta tesis es proponer algunas soluciones novedosas a diferentes problemas relacionados con NCSs. Todos los problemas considerados son típicos dentro del marco del control a través de redes, considerándose principalmente el de las pérdidas de paquetes en la transmisión de datos. Dentro del contexto de sistemas con pérdida de paquetes, se han estudiado diferentes problemas. Para obtener soluciones diferentes para este tipo de sistemas, se han considerado los siguientes objetivos: Diseño de controladores. Controladores Hinf, que consigan la robustificación de sistemas con incertidumbres. Controladores MPC, combinados con estrategias de buffer. Diseño de filtros. Filtros Hinf para sistemas con incertidumbres, usando técnicas frecuenciales y cadenas de Markov. Diseño de algoritmos. Localización dinámica de un control distribuido en una red formada por una estructura matricial de nodos. Localización dinámica del estimador de la salida del sistema, en una red formada por una estructura lineal de nodos. Estimación distribuida cooperativa. Basada en observadores locales de Luenberger. - Conclusiones Uno de los objetivos de esta tesis ha sido el análisis de la estabilidad y comportamiento de sistemas bajo control. En algunos casos, el diseño se ha realizado imponiendo restricciones en cuanto a la estabilidad. La robustificación de sistemas, en particular la de aquellos con incertidumbres, ha sido también tenida en cuenta. Las técnicas de control Hinf se han usado en los casos de análisis y diseño de sistemas de control. Otro objetivo importante de esta tesis ha sido el diseño de algoritmos para una red dinámica, la cual está compuesta por cierta estructura de nodos. El algoritmo es capaz de decidir qué nodo será el controlador o el estimador de la salida del sistema en la red. La estabilidad y el comportamiento del sistema de control ha sido analizado. También se ha abordado el diseño de estimación y esquemas distribuidos. Se han considerado redes que introducen retrasos temporales, junto con pérdidas aleatorias. La reducción en el consumo de energía ha sido un objetivo importante en esta parte de la tesis. En este caso, se ha examinado una política de comunicación entre agentes basada en eventos, la cual da lugar a un compromiso entre el comportamiento del sistema y los ahorros en la comunicación

Analysis of Large-Scale Asynchronous Switched Dynamical Systems

This dissertation addresses research problems related to the switched system as well as its application to large-scale asynchronous dynamical systems. For decades, this switched system has been widely studied in depth, owing to the broad applicability of the switched system framework. For example, the switched system can be adopted for modeling the dynamics of numerous systems including power systems, manufacturing systems, aerospace systems, networked control systems, etc. Despite considerable research works that have been developed during last several decades, there are still remaining yet important and unsolved problems for the switched systems. In the first part of this dissertation, new methods are developed for uncertainty propagation of stochastic switched systems in the presence of the state uncertainty, represented by probability density functions(PDFs). The main difficulty of this problem is that the number of PDF components in the state increases exponentially under the stochastic switching, incurring the curse of dimensionality. This dissertation provides a novel method that circumvents the issue regarding the curse of dimensionality. As an extension of this research, the new method for the switching synthesis is presented in the second part, to achieve the optimal performance of the switched system. This research is relevant to developing the switching synthesis on how to switch between different switching modes. In the following chapters, some interesting applications that emerges as today's leading-edge technology in high-performance computing (HPC) will be introduced. Generally, the massive parallel computing entails idle process time in multi-core processors or distributed computing devices as up to 80% of total computation time, owing to the synchronization of the data. Thus, there is a trend toward relaxing such a restriction on synchronization penalty to overcome this bottleneck problem. This dissertation presents a synchronous computing algorithms as a key solution to Leverage the computing performance to the maximum capabilities. The price to Pay for adopting the asynchronous computing algorithms is, however, unpredictability of the solution due to the randomness in the behavior of asynchrony. In this dissertation, the switched system is employed to model the characteristics of the asynchrony in parallel computing, enabling analysis of the asynchronous algorithm. Particularly, the analysis will be performed for massively parallel asynchronous numerical algorithms implemented on 1D heat equation and large-scale asynchronous distributed quadratic programming problems. As another case study, this switched system is also implemented on the stability analysis of large-scaled is tribute networked control systems (DNCS) having random communication delays. For these problems, the convergence or stability analysis is carried out by the switched system framework. One of major concerns when adopting the switched system framework for analysis of these systems is the scalability issues associated with extremely large switching mode numbers. Due to the massive parallelism or large-scale distributed nodes, the switching mode numbers are beyond counting, leading to the computational intractability. The proposed methods are developed targeting the settlement of this scalability issue, which inevitably takes place in adopting the switched system framework. Thus, the primary emphasis of this dissertation is placed on the mathematical development of computationally efficient tools, particularly for analysis of the large-scale asynchronous switched dynamical system, which has broad applications including massively parallel asynchronous numerical algorithms to solve ODE/PDE problems, distributed optimization problems, and large-scale DNCS with random communication delays