Piezoelectric actuators are well suited for active vibration control. They exhibit a high frequency range, good power density and high forces. Piezoelectric actuators can be applied in two fundamentally different configurations. First, the actuator can be mounted between a supporting structure and the system in which the vibration is to be controlled. However, in this configuration the actuator has to bear the static load of the system. In addition, it may be difficult to find a suitable support to which the actuator can be attached.
In many cases, the second configuration is more efficient. Here, the actuator is attached to the system on one end. The other end of the actuator is connected to a small mass made of any dense material. This configuration is known as an inertial mass actuator. The actuator can displace the inertial mass freely. Any acceleration of the inertial mass requires a force of the actuator proportional to the acceleration. By the principle of action and reaction, the opposite force acts on the structure the actuator is attached to. Therefore an inertial mass actuator can apply forces to any structure at any location without the need of a support.
The maximum force of an actuator depends on the frequency of the force signal. An actuator between the system and a support has an advantage at low frequencies, where an inertial mass actuator cannot apply any significant force. At high frequencies, the inertial mass actuator offers better performance. The performance depends also on the power amplifier needed to drive the piezo stack actuator. Therefore, the characteristics of piezoelectric inertial mass actuators are of great interest in the context of active vibration control.