Optimal modal damping control of truss structures using variable friction damper

Abstract

An optimal modal damping control is presented to reduce transient vibrations of a truss structure by which maximum modal damping of the lowest bending mode can be retained as vibration amplitude is reduced. The key idea is to represent the equivalent damping ratio of the truss structure with a friction damper in terms of the modal amplitude and normal force, then, to adjust the normal force for maximum modal damping as the amplitude decreases. This control is implemented in modal domain to maximize overall damping of the truss structure-friction damper system. These are major differences with previous researches, in which the normal force is controlled in physical domain to improve local energy dissipation in the friction damper. Performance of the proposed control technique is evaluated through experiments in terms of settling time and damping ratio of the first mode, which are compared with those by passive, bang-bang and sticking avoidance control to show its effectiveness.