Semi-passive and semi-active vibration control using new amplified piezoelectric actuators

In space and automotive applications, the use of piezoelectric actuators is limited because of the high voltages the actuators usually require (over one thousand volts) and the low displacement levels they can achieve (about ten micrometers). We designed a series of Amplified Piezoelectric Actuators (APAs) that overcome these two drawbacks. These APAs operate with an input voltage less than 200V because they employ a multilayer technology, and they offer displacement levels ten times greater than Direct Piezoelectic Actuators (DPAs), their direct-actuation counterparts. Part One of this paper is a brief of APA and DPA designs and characteristics. APAs have promising applications in the field of semi-passive and semi-active vibration damping. These damping techniques are based on a combination of piezoelectric material and passive (no power supply required) or active (a power supply is required) electrical networks. In both cases, damping is obtained when the piezoelectric material converts the mechanical energy resulting from the vibration into electrical energy (via the direct piezoelectric effect). This electrical energy is then dissipated, by Joule effect, into a resistive shunt (semi-passive damping) or into more sophisticated electrical networks, such as simulated inductances, negative capacitances, etc. (semi-active damping). Part Two of this paper compares the results obtained using various electrical networks in combination with an APA. Another application where APAs offer better performance than DPAs is in the field of semi-active vibration isolation. In part Three of this paper, we show that a semi-active system can be added to a passive elastic suspension to increase its performance. In this configuration, the APA is inserted between the vibration source and the system that is to be isolated. The active electrical network provides a simulated negative capacitance which compensates for the dielectric and the motional capacitances of the APA. The low stiffness obtained over a wide range of frequencies allows the APA to reduce the vibration that is transmitted from the source to the system.