Fabio Casciati

Fuzzy control of structural vibration. An active mass system driven by a fuzzy controller

The authors are engaged in a long-term research project studying the potential of fuzzy control strategies for active structural control in civil engineering applications. The advantage of this approach is its inherent robustness and its ability to handle the non-linear behaviour of the structure. Moreover, the computations for driving the controller are quite simple and can easily be implemented into a fuzzy chip. In this paper attention is focused on the response of a three-storey frame, subjected to earthquake excitation, controlled by an active mass driver located on the top floor. The design and the implementation of the controller driving the AMD system are discussed.

Active and semi-active control of structures – theory and applications: A review of recent advances

It is internationally recognized that structural control was introduced in civil engineering through a pioneering article by Yao and through the implementations promoted by Kobori. The concepts of active and semi-active structural control in civil and infrastructure engineering date back 40 years and much progress has been recorded during these four decades. Periodically, state-of-the-art manuscripts have been published and technical books were also printed to testify the maturation of the topic. This article only covers the period from the second semester of 2009 to the first semester of 2011, emphasizing the developments in terms of theoretical, numerical and experimental studies, as well as the use of control algorithms and devices in actual implementations. It is observed that there are still several operational limitations to prevent from the expected growth of the applications in standard design. Nevertheless, some innovative concepts help to foresee future developments within special sectors of applications.

Performance of Multi-TMD in the Towers of Suspension Bridges:

The convenience of Tuned Mass Dampers for the reduction of the gust response is investigated for the case of the towers of suspension bridges. For this special typology the design must pursue effectiveness, robustness and redundancy performance. Suitable solutions are multi-device provisions (MTMD), with distributed mass, frequency and damping. Increasing the robustness of MTMD against mistuning beyond the optimal configuration produces a loss of efficiency: as a result the final choice is determined only at the end of the constructive process. A brief discussion is reported on the weak performance to seismic excitation.

Technology of Semiactive Devices and Applications in Vibration Mitigation: Casciati/Technology of Semiactive Devices and Applications in Vibration Mitigation

List of Figures. List of Tables. List of Algorithms. List of Symbols. Introduction. Objectives. Organization of the Book. 1 Reliability, Robustness and Structural Control. 1.1 Preliminary Concepts. 1.2 Definitions. 1.3 System Representation. 1.4 A Comparison of Passive, Active and Semiactive Control Strategies. 2 Collocated and Non-collocated Systems. 2.1 Introduction. 2.2 Definition of Collocated System. 2.3 Centralized and Non-centralized Systems. 2.4 Linear and Non-linear Systems. 2.5 The Problem of Spillover. 2.6 Advantages and Disadvantages of Collocated and Non-collocated Systems. 2.7 A Numerical Comparison. 3 Semiactive Devices. 3.1 The Basic Idea and a Brief History. 3.2 Variable Viscous Devices. 3.3 Variable Stiffness Devices. 3.4 Magnetorheological Devices. 3.5 Friction Devices. 3.6 Tuned Liquid Dampers. 3.7 Electro-inductive Device. 3.8 Air-jet Actuators. 3.9 SMA Actuators. 4 Semiactive Control Laws. 4.1 Control Strategies and Algorithms for Semiactive Damping. 4.2 Implementation Schemes. 5 Implementation of Semiactive Control Strategies. 5.1 Introduction. 5.2 Hardware Control Implementation. 5.3 Real-time Software. 5.4 Non-centralized Control Versus Collocated Systems. 6 Experimental Verification. 6.1 Introduction. 6.2 The Challenges of Performance-based Design in Structural Testing. 6.3 Base-isolated Buildings and Bridges. 6.4 Supplemental Damping Devices. 6.5 Experimental Methods in Structural Dynamics. 6.6 Assessment of Structural Control Devices. 7 Stability and Foreseen Developments. 7.1 Preliminary Concepts. 7.2 Semiactive Features. 7.3 Conclusions. Appendix A: Damping. A.1 Types of Damping. A.2 Why Have a Damping Matrix? A.3 Rayleigh Damping. Bibliography. Index.

Stochastic dynamics of hysteretic media

Classic plasticity theory regards the yielding condition as discontinuity between elastic and plastic phases. This discontinuity leads obvious negative consequences in the mathematical features of the algorithm one uses in solving solid and structural mechanics problems.

Methods of stochastic structural dynamics

Abstract A concise review is given of the analytical methods of stochastic structural dynamics which deals with structural systems under time-varying random excitation. Included in the review are both linear and nonlinear structures and both parametric and non-parametric random excitations. Mathematically, parametric excitations appear in the coefficients for the unknowns in the equations of motion, whereas non-parametric excitations appear as inhomogeneous terms on the right hand side. Physically, random parametric excitations represent the variation of structural properties with time; therefore, they can affect the stability of structural response. Approximate methods are described for those cases for which exact solutions are presently not available.

Control of nonlinear structures using the fuzzy control approach

Active control of structures against environmental loads, such as earthquakes and wind, has received much attention in the last decade. Much of this research has involved development of control algorithms based on the assumption of exact knowledge of the system parameters, a condition that does not always exist in real-life applications. In addition, most of this research effort has focused upon linear control. Few active control strategies can effectively handle control of nonlinear behavior.Fuzzy logic control provides a promising opportunity for this purpose. This paper discusses the motivations for using a Fuzzy Logic Controller (FLC) and the guidelines for its design. A brief description of a FLC is first outlined to introduce the appropriate definitions. The application of fuzzy control to nonlinear structures is then illustrated. Some numerical examples are presented to study the controlled response of a hysteretic plane frame under earthquake loading.

Checking the Stability of a Fuzzy Controller for Nonlinear Structures

Standard strategies of active control were applied recently to civil engineering structures excited by environmental loads such as wind and earthquake. Attempts to overcome some technical inconvenience by the exploitation of suitable nonlinearities are in progress. Fuzzy controllers are potential candidates to drive the control in the presence of these structural nonlinearities. This paper pursues the identification of the stability checks to be conducted within the design process of such a fuzzy controller.

A new philosophy for stochastic equivalent linearization

Abstract An extension, to the time-dependent situation, of what is known in static structural reliability as the ‘normal tail approximation’ is presented. This is pursued within the classical stochastic equivalent linearization scheme. Duffing and hysteretic oscillators are studied in detail.

Semi-active Electro-inductive Devices: Characterization and Modelling:

Electro-inductive devices have recently been introduced to implement passive control schemes in special classes of structures. Their fascinating feature is the feasibility of large devices, to be installed, for instance, in long span bridges, much shorter than hydraulic dampers with identical maximum span. The characterization of an electro-inductive device with semi-active behavior is presented in detail in this paper. The paper also discusses ways of building a semi-active device, and details its passive control function.