Convex Formulation of Controller Synthesis for Piecewise-Affine Systems

This thesis is divided into three main parts. The contribution of the first part is to present a controller synthesis method to stabilize piecewise-affine (PWA) slab systems based on invariant sets. Inspired by the theory of sliding modes, sufficient stabilization conditions are cast as a set of Linear Matrix Inequalities (LMIs) by proper choice of an invariant set which is a target sliding surface. The method has two steps: the design of the attractive sliding surface and the design of the controller parameters. While previous approaches to PWA controller synthesis are cast as Bilinear Matrix Inequalities (BMIs) that can, in some cases, be relaxed to LMIs at the cost of adding conservatism, the proposed method leads naturally to a convex formulation. Furthermore, the LMIs obtained in this work have lower dimension when compared to other methods because the dimension of the closed-loop state space is reduced. In the second part of the thesis, it is further shown that the proposed approach is less conservative than other approaches. In other words, it will be shown that for every solution of the LMIs resulting from previous approaches, there exists a solution for the LMIs obtained from the proposed method. Furthermore, it will be shown that while previous convex controller synthesis methods have no solutions to their LMIs for some examples of PWA systems, the approach proposed in this thesis yields a solution for these examples. The contribution of the last part of this thesis is to formulate the PWA time-delay synthesis problem as a set of LMIs. In order to do so, we first define a sliding surface, then control laws are designed to approach the specified sliding surface and ensure that the trajectories will remain on that surface. Then, using Lyapunov-Krasovskii functionals, sufficient conditions for exponential stability of the resulting reduced order system will be obtained. Several applications such as pitch damping of a helicopter (2nd order system), rover path following example (3rd order system) and active flutter suppression (4th order system) along with some other numerical examples are included to demonstrate the effectiveness of the approaches

Impact Of The Internet On Internal Service Quality Factors: The Travel Industry Case

The growth of multichannel and pure-play companies attests to the changes that technology has brought to business processes. These changes have an effect on the quality of service delivery and customer satisfaction. In this qualitative study, the Service Quality Model was applied to gain insight into the internal service quality factors of two types of travel agencies. In addition, the impact of the Internet on quality of service was explored. The findings have theoretical and managerial implications.

Cues adopted by consumers in examining corporate website favorability: an empirical study of financial institutions in the UK and Russia

The purpose of this paper is to explore, reconcile and depict corporate website favorability (CWF), its antecedents and consequences in the financial setting in the UK and Russia context. To achieve the goals of this study, the research adopted a mixed method research design by using a survey, which is supported by insights from in-depth interviews and focus group discussions. Exploratory factor analysis (EFA), confirmatory factor analysis (CFA) and Structural equation modeling (SEM) were applied to gain insight into the various influences and relationships. The paper develops and empirically validates the framework of CWF antecedents and consequences. The paper indicates essential guidance for cross-functional managers and designers regarding the integrated and holistic utilization of building favorable corporate websites as part of the corporate identity management. The paper adds to the understanding of CWF and discusses the antecedents of CWF by drawing upon the existing literature. Furthermore, it offers possible consequences of CWF and provides a framework for future testing

A holistic framework of corporate website favourability

This paper extends the current knowledge of corporate website favourability (CWF) by developing a comprehensive conceptual model of its influence on corporate image, corporate reputation, loyalty and identification. The paper reviews previous studies on corporate websites from the perspectives of marketing, management, corporate identity and corporate visual identity in order to inform our understanding of the antecedents and consequences of CWF. The propositions and the conceptual framework present an approach by which a corporation can design and manage a favourable corporate website. A number of important contributions are offered: First, the paper adds to the understanding of CWF; second, it discusses the antecedents of CWF by drawing upon the existing literature; third, it is beneficial for practitioners in shaping CWF strategies, and fourth, it offers possible consequences of CWF and provides a framework for future testing

Scalable techniques for the computation of viable and reachable sets : safety guarantees for high-dimensional linear time-invariant systems

Reachability analysis and viability theory are key in providing guarantees of safety and proving the existence of safety-preserving controllers for constrained dynamical systems. The minimal reachable tube and (by duality) the viability kernel are the only constructs that can be used for this purpose. Unfortunately, current numerical schemes that compute these constructs suffer from a complexity that is exponential in the dimension of the state, rendering them impractical for systems of dimension greater than three or four. In this thesis we propose two separate approaches that improve the scalability of the computation of the minimal reachable tube and the viability kernel for high-dimensional systems. The first approach is based on structure decomposition and aims to facilitate the use of computationally intensive yet versatile and powerful tools for higher-dimensional linear time-invariant (LTI) systems. Within the structure decomposition framework we present two techniques – Schur-based and Riccati-based decompositions – that impose an appropriate structure on the system which is then exploited for the computation of our desired constructs in lower-dimensional subspaces. The second approach is based on set-theoretic methods and draws a new connection between the viability kernel and maximal reachable sets. Existing tools that compute the maximal reachable sets are efficient and scalable with polynomial complexity in time and space. As such, these scalable techniques can now be used to compute our desired constructs and therefore provide guarantees of safety for high-dimensional systems. Based on this new connection between the viability kernel and maximal reachable sets we propose a scalable algorithm using ellipsoidal techniques for reachability. We show that this algorithm can efficiently compute a conservative under-approximation of the viability kernel (or the discriminating kernel when uncertainties are present) for LTI systems. We then propose a permissive state-feedback control strategy that is capable of preserving safety despite bounded input authority and possibly unknown disturbances or model uncertainties for high-dimensional systems. We demonstrate the results of both of our approaches on a number of practical examples including a problem of safety in control of anesthesia and a problem of aerodynamic flight envelope protection.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat