310 PASSIVE AND SEMI-ACTIVE CONTROL OF SELF-EXCITED OSCILLAIONS BY TRANSFER OF INTERNAL ENERGY TO HIGHER MODES OF VIBRATION

概要

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This paper presents a remedy to control wind-induced self-excited oscillations of long and flexible structures with low internal damping, such as cables. A simple magnetic or mechanical device is used to disturb the motion in the lower modes of vibration in order to transfer a portion of the internal energy to higher modes. It is assumed that the aerodynamic damping of the higher modes of vibration is positive for the wind velocities at which the lower modes develop aeroelastic instabilities. This assumption is reasonable with vortex-induced vibration (the lock-in phenomenon occurs when the vortex shedding frequency approaches a natural frequency of the vibrating structure) and with galloping, if the modal damping is in the same orders in all modes of vibration. In these cases, the onset wind velocity increases with the natural frequency of the mode. Because of the positive aerodynamic damping of the higher modes of vibration, the energy transferred from lower modes to higher modes is dissipated in high frequency decay, thus reducing the overall amplitude of oscillation of the cable. In an analytical study of a two-degree-of-freedom model, the authors gave the main characteristics of a passive control using energy transfer. To improve the performance by optimizing the energy transfer, semi-active control schemes are proposed and tested on a cable via simulation, in the case of galloping forces.
一般社団法人日本機械学会の論文
2001-04-20