Vibration suppression of space structures is an important and challenging problem because the operational requirements are very high whereas the structural damping is expected to be small. The space structures often consist of truss elements which are connected by bolted joints. These junctions turn out to be the major sources of damping. Energy is dissipated in such joints primarily by dry (unlubricated) friction acting at the interface of the connected parts. In the present paper the design of enhanced friction joints for vibration suppression is investigated using semi-active friction elements. The use of active control to vary the normal contact force in a joint by using a piezoelectric element is explored. The technology is termed semi-active because it uses active control to vary the properties of a passive element. Closed-loop semi-active systems are guaranteed to be stable since the control system is 'passive'. A local control law based on an algebraic friction model is implemented in a hybrid MBS (Multibody System) of a triangular truss structure. The structural response is decomposed into large rigid body motion and small elastic deformations. The equations of motion are linearized w.r.t. the deformation coordinates. The flexibility of the MBS is treated by superposition of structural modes calculated by FEM (Finite Element Method) in the sense of a Ritz approximation. To illustrate the efficiency of the semi-active dry friction damper, simulation results for free as well as for forced vibrations of flexible structures with active joints are presented.
Semi-active vibration control of flexible structures
Die semi-aktive Schwingungsdämpfung von flexiblen Strukturen
1998
10 Seiten, 6 Bilder, 1 Tabelle, 11 Quellen
Aufsatz (Konferenz)
Englisch
Raumfahrttechnik , Schwingungsdämpfung , aktives Bauelement , Gitterstab , Schraubverbindung , Trockenreibung , Kontaktkraft , Rechenmodell , Regelungssystem , Modalanalyse , Dreieck , elastische Verformung , Bewegungsgleichung , Linearisierung , Finite-Elemente-Methode , Rechnersimulation , Mehrkörpersystem , Reibungsdämpfer
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