Multi-modal vibration control using adaptive positive position feedback

Abstract

An adaptive controller, Adaptive Positive Position Feedback (APPF) is proposed for the multi-modal vibration control of frequency varying structures. Spillover phenomena and real-time system identification have been obviously difficult obstacles for the multi-modal adaptive vibration control. To overcome these problems, a fast and powerful algorithm is proposed to identify the frequencies of time-varying structures. Variable PPF controllers are adjusted with estimated natural frequencies at every time step. A composite plate with a bonded piezoelectric sensor and an actuator was prepared as an experimental model, and the natural frequencies of the model are changed by attaching masses. The experimental results show that natural frequencies are estimated quite accurately and that the vibration of controlled modes is significantly reduced. No significant performance reduction has been observed with respect to approximately 10% frequency changes of the corresponding modes. On the contrary, the performance of the conventional LQG controller is significantly degraded due to frequency variations.