Design of a Switching Controller for Adaptive Disturbance Attenuation with Guaranteed Stability

In this paper, a new algorithm is proposed for the design of a family of controllers to be used within an adaptive switching control scheme. The resulting switching controller is able to attenuate the effects of disturbances having uncertain and possibly time-varying characteristics, as well as to ensure stability under arbitrary switching sequences. Specifically, the stability requirement is addressed within the synthesis of the set of controllers by imposing some constraints in LMI form. The overall synthesis algorithm is formulated in terms of convex optimization problems, which can be solved by means of standard tools. The validity of the proposed solution is underlined by showing simulation results on an adaptive optics case study

Multi-model unfalsified adaptive switching supervisory control

The paper studies how on-line inferring stability of a potential control-loop consisting of an uncertain plant interconnected in feedback with a candidate controller using plant I/O pairs recorded while the plant is possibly driven by a different controller. In such a context, a convenient tool to work with is to resort to the conceptual entity of a virtual reference (VR). The adopted approach consists of embedding, in the so-called unfalsified adaptive switching control schemes based on VR, a family of nominal models pairwise associated with the given candidate controllers. The result is that the supervised switching mechanism can moderate the chance that destabilizing controllers be switched-on and, hence, reduce both the magnitude and time durations of “learning” transients after start-up, while, in contrast with pre-existing multi-model based methods, stability in-the-large is guaranteed under the minimal conceivable assumption that a stabilizing candidate controller exist.

A New Approach to Multi-Model Adaptive Control

Adaptive control is an approach used to deal with systems with uncertain or time-varying parameters. A classical adaptive controller typically consists of a linear time-invariant (LTI) control law together with a tuning mechanism which adjusts its parameters. Usually, though not exclusively, discrete-time adaptive controllers provide only asymptotic stability and possibly bounded-noise bounded-state stability; neither exponential stability nor a bounded noise gain is typically proven. Recently it has been shown that if we employ a parameter estimator based on the original Projection Algorithm together with projecting the parameter estimates onto a given compact and convex set, then the adaptive controller guarantees linear-like closed-loop behavior: exponential stability, a bounded noise gain and a convolution bound on the exogenous inputs. In this thesis, the overarching objective is to show that we can prove these same desirable linear-like properties in a wide range of adaptive control problems without the convexity assumption: the main idea is to use multiple estimators and a switching algorithm. Indeed, we show that those properties arise in a surprisingly natural way. We first prove a general result that exponential stability and a convolution bound on the closed-loop behavior can be leveraged to show tolerance to a degree of time-variations and unmodelled dynamics, i.e. such closed-loop properties guarantee robustness. After reviewing the original Projection Algorithm and introducing the reader to our slightly revised version, we turn our attention to controller design, with a focus on a non-convex set of plant uncertainty. As a starting point, we first consider first-order plants incorporating a simple switching algorithm. We then extend the approach to a class of nonlinear plants (which have stable zero dynamics); we consider both cases of convex and non-convex sets of parameter uncertainty. Afterwards, we turn to possibly non-minimum phase LTI plants; first we consider the stabilization problem for which we have two convex sets of uncertainty; then, we turn to the problem of tracking the sum of a finite number of sinusoids of known frequencies subject to an unknown plant order and a general compact set of uncertainty

Ingegneri & Ingegneria a Firenze

The initial idea for this volume was born while rethinking the organisation of the University of Florence following the recent reform, with the aim of retracing the evolution of the Faculty of Engineering throughout its 40 years, telling and documenting its history, collecting memories and documents from a period characterised by significant changes. The research carried out by the curators and many colleagues has progressively broadened the horizon of the work to collect not only the contents of the academic history but also those of the "civil" history of the Faculty, observing its laborious growth, affirmation and consolidation in the Florentine University, and also noting the relationships with the social and economic context (the city, the region, the national and international involvement) that surrounds a significant collective entity such as “our” Faculty of Engineering. This made it possible to explore and document relevant areas that are fundamental for a non-trivial knowledge of how many actors have crossed the scenario of the Faculty and of which phenomena the Faculty itself has been an observer and protagonist. Thus, the work has been enriched with a great number of contents, declined in each chapter with pleasant energy and that are difficult to summarise in a purely historical or celebratory paradigm. If we try and visualise the readers of this volume, we think of those who will find there the path of their life, who will there find the roots of the present and who will want to discover the reasons for the future

Ingegneri & Ingegneria a Firenze

This volume takes up part of the content of the one published on the occasion of the 40th anniversary of the foundation of the Faculty of Engineering of the University of Florence and constitutes, after 10 years, only for the first and second part of that volume, the natural continuation with all the necessary updates, while the third part will be resumed in a new volume. These 10 years have been characterized by a reform of the University which has significantly changed its structure with the abolition of the Faculties and the transfer of teaching organization to the Departments which, as it is well known, were originally constituted only as research bodies. This evolution will be discussed in the new volume