The development of a novel piezoelectric induced-strain actuator possessing an innovative internal amplifying structure is presented in this paper. This actuator basically consists of a metal frame and two lead zirconate titanate (PZT) piezoelectric ceramic patches. The metal frame is bent to form an open trapezoid, where its center part has a specially designed saddle-like unit and its slanting legs are attached with PZT patches. The saddle-like unit has an amplifying-lever mechanism at the corners to increase the displacement output of the whole actuator even its legs are mechanically clamped. When an electric field is applied across the thickness of the PZT patches, the patches induce deformations on the whole actuator through the piezoelectric d31 effect. The saddle-like unit can relax the constraints at the joints between the unit and the legs by stretching itself during bending. Piezoelectric finite element analysis is used to maximize the work output of displacement and blocked force of the actuator under different geometric parameters. The results are in good agreement with those obtained from quasi-static measurements, showing that the actuator has work output comparable to and larger than the existing induced-strain actuators (e.g., THUNDER) under fixed mounting conditions. Therefore, the actuator has great potential for use in various practical smart structures and integrated systems, including active-passive vibration isolation and micro-positioning.
A novel tunable mass damper (TMD) is developed using the sensitivity of transversal bending stiffness and resonance frequencies of a beam to its axial force. This smart TMD consists of a force actuator-sensor unit suspended in a rigid frame by two flexible beams coupled to the axial ends of the unit and the frame. The force actuator-sensor unit is composed of a giant magnetostrictive composite-based force actuator for producing an axial force to the beams and a pair of piezoelectric ceramic-based force sensors for generating a tuning signal. Through adjusting the magnetic field strength applied to the force actuator to change the axial force exerted on the beams, the transversal bending stiffness of the beams and hence the natural frequency of the smart TMD is tuned. In this paper, the design, fabrication, and characterized of the smart TMD is described. The measured resonance frequency of the smart TMD is 65 Hz at zero magnetic tuning field and 50 Hz at an applied magnetic field of 686 Oe. Tunability of the resonance frequency as high as 23 % is achieved with the reasonably low magnetic tuning field. The frequency response functions as measured using the force sensors agree well with those obtained using a commercial accelerometer, indicating a great possibility of directly deploying the force sensors for active or semi-active tuning or control purposes.