A resonant frequency tunable, extensional mode piezoelectric vibration harvesting mechanism

Abstract

Electrical power for distributed, wireless sensors may be harvested from vibrations in the ambient through the use of electromechanical transducers. To be most useful, the electromechanical transducer should maximize the harvested power by matching its resonant frequency to the strongest vibration amplitude in the source’s vibration spectrum. This paper introduces a new frequency tunable mechanism wherein the deformation of the piezoelectric elements is primarily in-plane extension, and bending effects may be neglected. The extensional mode resonator (XMR) is formed by suspending a seismic mass with two piezoelectric sheets. The mechanism is made frequency tunable by an adjustable link that symmetrically pre-tensions both piezoelectric sheets. A prototype XMR has been built and tested that has demonstrated adjustable and repeatable resonant frequency variation from 80 to 235 Hz. The electrical power generated by the XMR is also insensitive to the driving frequency, when the resonant frequency is matched to the driving frequency.

Toward Broadband Vibration-based Energy Harvesting

“…Rather than bending mode, some researchers also investigated the tunable resonator working in extensional mode, termed XMR (Morris et al, 2008;Youngsman et al, 2010).…”

“…The XMR presented by Morris et al (2008) was formed by suspending a seismic mass with two piezoelectric membranes (PVDF). Pre-tensioning two rectangular membranes (with dimensions of 2l×w×h and Young's modulus E) by a rigid link with length of 2u p and deflecting the link by Δu, as shown in Figure 6, the force-deflection characteristics of the rigid link was found to be ( )…”

Vibration Energy Harvesting: Linear and Nonlinear Oscillator Approaches

“…Various attempts to design tuneable harvesters have been proposed (Challa V.R. et al, 2008, Morris D. et al, 2008. Thus most of the present working solutions for vibration-to-electricity conversion are based on linear, i.e.…”

Design and fabrication of a novel resonant surface sensitive to out-of-plane forces for the indentation and injection of living cells

“…As in [10], we assume that small deflections of the beam about a mean deflection D s can be described approximately by a single stiffness value. An effective spring constant is found by deflecting the beam from its equilibrium position by an arbitrary amount ∆ d (see Fig.5), so that…”