Friction damping in bolted joint connections of large space structures turned out to be a major source of damping (Gaul and Bohlen, 1987). For vibration suppression, the joints are designed such that the normal force in a frictional interface is controlled which improves damping performance. The use of active control to vary the normal contact force in a joint by means of a piezoelectric element is explored. A model consisting of two elastic beams connected by a single active joint is considered. A friction model with velocity dependent dynamics is used to describe the friction phenomena. A control law for friction dampers which maximizes energy dissipation instantaneously by controlling the normal force at the friction interface is proposed. The effect of displacement- and velocity-induced friction dynamics is considered for the design of the control law. We arrive at a dynamic controller which prevents frictional energy stored as potential energy in a bristle model from being returned to the system.

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