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Event Triggered Control of Nonlinear Systems

  • Author / Creator
    Ghodrat, Mohsen
  • Event-triggered control systems have emerged as an important alternative to classical digital control systems, in which the flow of information between sensors, controller and actuators takes place aperiodically in an event-based manner. Event-triggered control (ETC) has seen much attention from the research community in recent years resulting in a comprehensive theory which includes stability analysis, disturbance rejection, control design, etc. This thesis is concerned with important theoretical and practical aspects of event-triggered systems that can be divided into two main categories. The first part includes the robust analysis of ETC systems involving different types of robustness measures. We start with designing a triggering condition (TC) for general nonlinear event-triggered systems in a way that an L2-type performance is guaranteed. The results are obtained in a local framework due to reliance on the assumption that the admissible disturbance is norm bounded by some function of the states. The results are then extended in two aspects. First, we study the Lp-stability of nonlinear event-triggered systems and second, we relax the restriction on the class of disturbances. In addition, the TC is proposed using a unifying framework which includes several dynamic and static parameters to cover several existing TCs proposed earlier in the literature as special cases. More importantly, the approach solves the non-trivial problem of isolating the triggering instants in presence of arbitrary disturbances. As another extension, the more interesting scenario of jointly designing the TC and control law is studied for nonlinear Lipschitz systems. Our solution to this problem includes both state and output-based feedback laws and consists of assigning the dominant eigenvalues of the stability matrices according to desired control demands.We also consider the robust analysis of nonlinear input-affine systems and study the input-to-state stability of ETC systems with respect to actuator noise/error and exogenous disturbances. We consider both the design of the TC for a pre-design controller as well as the more challenging simultaneous design of controller and TCs. Finally, we consider the concept of dissipativity as general framework in the study of various forms of robust performance and system properties (including passivity, ISS, and L2 gain performance), and study different forms of dissipativity for event-based network-communicated physical processes.The second category of results in this thesis focuses on the important problem of reducing the average sampling frequency for ETC systems. We study this problem from two points of view. First, we modify a pre-designed TC to effectively enlarge the intersampling intervals without violating the desired robust performance of the event-triggered system. Also, we obtain a lower bound on the amount of inter-event times extension. Moreover, for an ETC design to be successfully implemented in practice, the uniform isolation of triggering instants has to be guaranteed. This is even more challenging when disturbances are applied to the system. Our proposed triggering structure not only provides a general platform for the event design but also serves to the isolation of sampling instants in presence of arbitrary disturbances.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-tjth-4427
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.