Global effect of locally applied active damping illustrated by laser vibrometry

Abstract

Theoretical analysis suggests that decentralized active vibration damping implementing skyhook control (or advanced versions thereof), while applied locally, reduces vibration level over the whole structure by introducing modal damping. That was, however, never directly confirmed experimentally. Laser vibrometry, measuring vibration in multiple points in quick succession and referencing it to the excitation force, provides this opportunity. This paper reports theoretical considerations and experimental results illustrating reduction of total kinetic energy of all-steel optical breadboard by two active dampers. It had been shown (S. Elliott et al.) that the effect of collocated decentralized vibration control is limited by two phenomena: instability and “pinning.” These issues are analyzed by direct measurement of kinetic energy for a range of active control gains. Optimal gains minimizing kinetic energy with sufficient stability margin are demonstrated and discussed.Theoretical analysis suggests that decentralized active vibration damping implementing skyhook control (or advanced versions thereof), while applied locally, reduces vibration level over the whole structure by introducing modal damping. That was, however, never directly confirmed experimentally. Laser vibrometry, measuring vibration in multiple points in quick succession and referencing it to the excitation force, provides this opportunity. This paper reports theoretical considerations and experimental results illustrating reduction of total kinetic energy of all-steel optical breadboard by two active dampers. It had been shown (S. Elliott et al.) that the effect of collocated decentralized vibration control is limited by two phenomena: instability and “pinning.” These issues are analyzed by direct measurement of kinetic energy for a range of active control gains. Optimal gains minimizing kinetic energy with sufficient stability margin are demonstrated and discussed.