Piezoceramics-based Devices for Active Balancing of Flexible Shafts

This paper focuses on vibration control of flexible shafts by means of rotorfixed piezoelectric materials. The target is to realize compact solutions for the suppression of problematic resonant vibration at so-called flexural critical speeds. For analysis, parametric finite element models of flexible rotors with piezoceramic sheets and strain or displacement sensors are developed, where the number of degrees of freedom is kept low. Several mechanisms which can destabilize flexible rotors are quantisized, such as rotor material damping, dissipation of currents induced in rotor-fixed piezoceramics and active feedback control proportional to rotor strain rates. The effectiveness of low frequency feedback and feedforward control for the suppression of the unbalance response is demonstrated using analytic and experimental results. Emphasis is on the interaction between the dynamics of the rotor and that of the connected electronic circuits. The experimental setup which is used for validation is a flexible shaft equipped with piezoceramic sheets and strain sensors. A slipring assembly is used to simplify measurements with, and control of, the sensors and actuators on the shaft and to facilitate the development of compact drive electronics.