Optimal semi-active damping of cables with bending stiffness

Abstract

The problem of optimal semi-active damping of cables with bending stiffness isinvestigated with an evolutionary algorithm. The developed damping strategyis validated on a single strand cable with a linear motor attached close to theanchor position. The motor is operated in force feedback mode during free decayof cable vibrations, during which time the decay ratios of the cable modes aremeasured. It is shown from these experiments that the damping ratios predicted insimulation are close to those measured. The semi-active damping strategy found by theevolutionary algorithm is very similar in character to that for a cable withoutbending stiffness, being the superposition of an amplitude-dependent friction andnegative stiffness element. However, due to the bending stiffness of the cable,the tuning of the above elements as a function of the relevant cable parametersis greatly altered, especially for damper positions close to a fixed end anchor,where the mode shape depends strongly on bending stiffness. It is furthermoredemonstrated that a semi-active damper is able to dissipate significantly moreenergy for a cable with simply supported ends compared to fixed ends due tolarger damper strokes and thereby increased energy dissipation in the device.