Inertial Actuator with Virtual Mass for Active Vibration Control

Inertial actuators (IAs) are often used as control units in active noise and vibration control systems. It is wellknown that the IA’s natural frequency should be far below that of the structure under control to ensure good stability margins. However, under normal circumstances, an IA with low natural frequency either increases the additional weight or causes unwanted static displacement of the IA’s proof-mass. In this study, an IA with virtual mass is presented to reduce the IA’s natural frequency without changing its physical design. The virtual mass of the IA is realized by using the proof-mass acceleration feedback as a local loop within the IA. Thus, the IA’s natural frequency can be shifted to low frequency for active control application. The proposed IA with virtual mass is then applied to actively control a clamped beam’s vibration based on the velocity feedback control system. The experimental results show that the stability of the control system and the control performance can be improved significantly as the IA’s natural frequency is reduced with virtual mass.