Vibration Control and Periodic External Force Estimation for a Flexible Rotor Suspended by Piezoelectric Stack Actuators

Abstract

Piezoelectric actuators are feasible for vibration control of a flexible rotor because they can provide high forces despite their compact size, and their operating frequency range is quite large. When moderate damping is insufficient for a rotor-bearing system, near critical speeds, excessive vibrations may occur in trial runs of a balancing procedure or the phase angles of rotor displacement may vary considerably with rotational speed, making it impossible to measure their precise values. To overcome these issues, we developed a control system using multilayer piezoelectric actuators in order to suppress the vibration of a flexible rotor and to estimate its modal unbalances simultaneously. The H-infinity controller was designed to achieve robust performance for an uncertainty of the system, and its damping ability was examined in simulation. Large reductions were observed in the response near resonance. Then, steady-state responses of the system excited by sinusoidal forces were calculated to investigate the estimation accuracy of sinusoidal external forces, and good agreement was observed between the estimated and the theoretical results. Furthermore, it was demonstrated that feedforward plus feedback control using the estimated modal force significantly improved the performance of suppression of flexible rotor vibrations compared with simple feedback control.