An apparatus for use in low frequency vibration energy harvesting (VEH) and with actuators requiring a low deflection force. The apparatus includes a piezo flexure that is loaded with a compressive pre-load force to place the piezo flexure under compression. The piezo flexure may be supported at an intermediate point or at one end thereof. The compressive pre-load force produces flexes the piezo flexure into one or the other of two stable positions, these positions being offset on opposite sides of a longitudinal centerline representing the position of the piezo flexure that would be produced without the compressive pre-load force applied thereto. The compressive pre-load effectively provides a negative spring constant which "softens" the piezo flexure and enhances a responsiveness of the piezo flexure to low frequency vibration energy. The piezo flexure also operates over a much wider frequency bandwidth than conventional systems incorporating a tip mass.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Patent Application Ser. No. PCT/US/2004/025049 filed Jul. 30, 2004, which in turn claims priority from U.S. Patent Provisional Application No. 60/491,122 filed Jul. 30, 2003, the disclosures of which are incorporated herein by reference.
