Semi-active control of friction dampers has been proposed to improve the energy dissipation characteristics of passive friction dampers and to broaden the areas of application in which they can successfully be used. In this paper, we propose control laws for friction dampers which maximize energy dissipation in an instantaneous sense by modulating the normal force at the friction interface. In particular, we consider the effect of displacement- and velocity-induced friction dynamics on the design of the control law. A dynamic controller is proposed that prevents stored frictional energy from being returned to the system. Using both simulation and experimental results, we demonstrate under what operating conditions friction dynamics are vital to the control problem and, for these conditions, demonstrate the efficacy of the proposed controller. Furthermore, the experiments reveal that control strategies which, unlike instantaneous optimization, take system dynamics into account could lead to significant additional improvements in energy dissipation.
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Dupont et al. (1997) studied this question.