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II Vibration Control Nejat Olgac 181 © 2002 by CRC Press LLC 11 Active Damping of Large Trusses 11.1 11.2 Introduction Active Struts Open-Loop Dynamics of an Active Truss • Integral Force Feedback • Modal Damping • Experimental Results A. Preumont Université Libre de Bruxelles 11.3 Active Tendon Control Active Damping of Cable Structures • Modal Damping • Active Tendon Design • Experimental Results Frederic Bossens Université Libre de Bruxelles Nicolas Loix Micromega Dynamics 11.4 11.5 11.6 Active Damping Generic Interface Microvibrations Conclusions Abstract This chapter reviews various ways of damping large space trusses. The first part discusses the use of active struts consisting of a piezoelectric actuator collocated with a force sensor. The guaranteed stability properties of the integral force. | II Vibration Control Nejat Olgac 2002 by CRC Press LLC 11 Active Damping of Large Trusses A. Preumont Université Libre de Bruxelles Frederic Bossens Université Libre de Bruxelles Nicolas Loix Micromega Dynamics 11.1 Introduction 11.2 Active Struts Open-Loop Dynamics of an Active Truss Integral Force Feedback Modal Damping Experimental Results 11.3 Active Tendon Control Active Damping of Cable Structures Modal Damping Active Tendon Design Experimental Results 11.4 Active Damping Generic Interface 11.5 Microvibrations 11.6 Conclusions Abstract This chapter reviews various ways of damping large space trusses. The first part discusses the use of active struts consisting of a piezoelectric actuator collocated with a force sensor. The guaranteed stability properties of the integral force feedback are reviewed and the practical significance of the modal fraction of strain energy is stressed. The second part explains the concept of active tendon control of trusses the similarity of this concept with the previous one is pointed out. The third part describes an active damping generic interface based on a Stewart platform architecture with piezoelectric legs. The similarity with the previous concepts is emphasized. Finally the damping of microvibrations is briefly discussed. 11.1 Introduction The development of future generations of ultralight and large space structures will probably not be possible without active damping enhancement of the structures and active isolation of the scientific payloads that are sensitive to vibrations. Interferometric missions are an example particularly stringent geometric stability requirements.1 2 This chapter addresses the problem of active damping of large trusses with three different concepts i active strut ii active tendon and iii generic interface. In all cases the same control architecture is used a collocated piezoelectric actuator and force sensor connected by a local controller with an integral force feedback IFF . 11.2 Active Struts