An experimentally validated bimorph cantilever model for piezoelectric energy harvesting from base excitations

• Published in: Smart materials and structures Vol. 18; no. 2; pp. 025009 - 025009 (18)
• Main Authors: Erturk, A, Inman, D J
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.02.2009; Institute of Physics
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Measurement and testing methods; Physics; Servo and control equipment; robots; Solid mechanics; Structural and continuum mechanics; Transducers; Resistors; Bimorph transducer; Energy recovery; Euler equations; Response functions; Rayleigh-Ritz methods; Steady state; Piezoceramic materials; Exact solution; Vibrations; Short circuit; Added mass; Coupled modes; Modelling; Frequency response; Sinusoidal excitation; Distributed parameter systems
• DOI: 10.1088/0964-1726/18/2/025009
• ISSN: 0964-1726

Piezoelectric transduction has received great attention for vibration-to-electric energy conversion over the last five years. A typical piezoelectric energy harvester is a unimorph or a bimorph cantilever located on a vibrating host structure, to generate electrical energy from base excitations. Several authors have investigated modeling of cantilevered piezoelectric energy harvesters under base excitation. The existing mathematical modeling approaches range from elementary single-degree-of-freedom models to approximate distributed parameter solutions in the sense of Rayleigh-Ritz discretization as well as analytical solution attempts with certain simplifications. Recently, the authors have presented the closed-form analytical solution for a unimorph cantilever under base excitation based on the Euler-Bernoulli beam assumptions. In this paper, the analytical solution is applied to bimorph cantilever configurations with series and parallel connections of piezoceramic layers. The base excitation is assumed to be translation in the transverse direction with a superimposed small rotation. The closed-form steady state response expressions are obtained for harmonic excitations at arbitrary frequencies, which are then reduced to simple but accurate single-mode expressions for modal excitations. The electromechanical frequency response functions (FRFs) that relate the voltage output and vibration response to translational and rotational base accelerations are identified from the multi-mode and single-mode solutions. Experimental validation of the single-mode coupled voltage output and vibration response expressions is presented for a bimorph cantilever with a tip mass. It is observed that the closed-form single-mode FRFs obtained from the analytical solution can successfully predict the coupled system dynamics for a wide range of electrical load resistance. The performance of the bimorph device is analyzed extensively for the short circuit and open circuit resonance frequency excitations and the accuracy of the model is shown in all cases.