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Two typical characteristics of direct piezoelectric actuators are displacements of ten micrometers and high stiffnesses. Recently, multilayer actuators have been improved, and they now display strains of approximately 1200 ppm at low excitation levels (less than two hundred volts). Thus, they are well suited to perform precise positioning of optical devices. But for industrial needs, this performance is still insufficient for positioning devices with larger displacements (in the range of several hundred micrometers). Numerous designs of mechanical amplifier devices based on the use of flexural hinges have been proposed. Due to their low stiffness, these devices cannot be used in space applications because they would not survive during takeoff. The amplified piezoelectric actuator which we designed and tested, eliminated the low stiffness drawback and ensures good force transmission. Due to the stiffness of the amplifier, the efficiency of the electromechanical transduction is significantly higher than those of conventional amplifier mechanisms. To design this actuator, we performed a numerical finite element simulation that included the piezoelectric effect. Among other things, this model shows the displacement as a function of the excitation and the electrical admittance. The static and the dynamic behaviors were determined. The main features of the actuator are a no-load displacement of 180 micrometers and stiffness of 5 N/m. These characteristics were experimentally verified using an electromechanical test bench including a laser Doppler interferometer, thus confirming the design method. Technological aspects, like the compressive force applied to the piezoelectric material, were considered. Many applications for this amplified actuator already exist. For example, an active mechanism using this actuator can be used to tilt a mirror. Another application of the amplified actuator is in the field of active damping of structures. In this case, the actuator is connected to a resistive shunt so that electrical damping is obtained through the direct piezoelectric effect. The experimental results show that the actuator is interesting because of its high electromechanical coupling, and, consequently, its ability to perform active damping.
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