Piezoelectric Micro-power Generator Research Articles

Quality and Damping Factors Optimization Using Taguchi Methods in Cantilever Beam Based Piezoelectric Micro-Power Generator for Cardiac Pacemaker Applications

Piezoelectric Micro-Power Generator (PMPG) can produce electrical power as a result of piezoelectric effects. Moreover, producing self-powering devices, especially in small electronic devices with low power requirements such as cardiac pacemakers is one of the objectives of the study. This paper optimizes the quality and damping factors for PMPG by using the Taguchi optimization method instead of a trial and error approach. Eight physical control parameters with three levels, including PMPG layer materials and dimensions are selected in order to study the influence of each parameter of PMPG quality and damping factors. Level eighteen Orthogonal arrays is based on signal-to-noise ratio which is conducted and confirmed by using analysis of variance in determining the PMPG with the best quality and damping factor.18 experiments are conducted with three trials using COMSOL Multiphysics software ver. 5.4 for each one. The PMPG maximum quality factor, the lower damping factor, and the highest efficiency are designed at 1.35 Hz, which is equivalent to 81 beats per min. Both Taguchi and the analysis of variance results conclude that the highest PMPG physical control parameters affect the quality and damping factors at 1.35 Hz from higher to lower order as follows: insulator width of 0.12 mm, 0.2 mm piezoelectric layer width, 20 µm of insulator thickness, 2.5 mm of proof mass thickness, piezoelectric material of PZT5A, piezoelectric layer thickness of 60 µm, proof mass material of aluminum, and 5 mm proof mass length respectively. COMSOL Multiphysics is used again to study the PMPG with the best parameters, the PMPG resonates at 1.35 Hz, 5.78 Hz, 7.61 Hz, 32.54 Hz, 424.21 Hz, and 448.59 Hz respectively with a different mode of deflections by using Eigen’s frequency analysis. The high electric field, the electric energy density, and hence the output power are produced at first resonance frequency at 1.35 Hz in the range of 0.5-2.5 Hz by using frequency response analysis. Transient analysis is conducted at 1.35 Hz, which shows that the PMPG reaches the steady-state after seven seconds of sinusoidal signal excitation with quality factor of 166.67 and damping factor of 0.003. This improves that PMPG works nearly at no damping system and keeps oscillating for a long time before stopping for a single excitation, which opens the door widely in front of fabricating self-powered devices that have been working for a long time, which make them suitable to replace lithium iodide battery in cardiac pacemakers

Vibration-based piezoelectric micropower generator for power plant wireless monitoring application

This paper investigates the factors affecting the performance of a vibration based micropower generator for a power plant wireless monitoring application. A bimorph bender, one of micropower generator methods, was used in this work. The ANSYS program was used to study the distribution of stress–strain in each model design, and MATLAB was used to simulate and investigate the extracted power. Triangular, rectangular and trapezoidal cantilevers were chosen to analyse the effect of the bender shape on the power produced. The tests were conducted using the same input excitation conditions (10m/s2), frequency range of (50–150Hz). The effect of the configuration arrangement (horizontal and vertical) of the PZT bimorph cantilever on the power generation (poling series) was also investigated. The simulation result showed that the maximum stress–strain value was produced in the triangular bender shape with equal distribution on all the surface areas. The measurements’ results showed that the triangular cantilever produced maximum power compared to other bender shapes for both horizontal and vertical directions and single test. The horizontal and vertical arrangements of the cantilevers showed that the vertical arrangement could produce more power than the horizontal arrangement. The experimental results showed concurrence with theoretical models.

Design and optimization of cantilever based piezoelectric micro power generator for cardiac pacemaker

Piezoelectric micro-power generator (PMPG) converts mechanical vibration energy into electric energy via piezoelectric effects. In cardiac pace makers, the use of PMPG eliminates the need for a traditional lithium iodide battery replacement. In this paper we design and optimize PMPG that is able to harvest the mechanical movement of the heart beat to be converted into usable electrical power in frequency range 1---1.7 Hz. Eight control parameters are selected: which are proof mass material, piezoelectric material, proof mass length, proof mass thickness, piezoelectric layer width, piezoelectric layer thickness, silicon nitride layer width, silicon nitride layer thickness. Orthogonal arrays of Taguchi method for these eight parameters mentioned with three levels and signal-to-noise (S/N) ratio, and ANOVA analysis is studied to determine the optimum design. COMSOL Multiphysics ver. 4.2 is used in 18 different simulations. The maximum output power and highest efficiency designed at 1.2 Hz is equivalent to 72 beat per min. Both Taguchi and ANOVA confirms the same results of determining the parameter of having the most influence on the generated output power at 1.2 Hz in descending order: which are piezoelectric material of PZT-5A, proof mass length of 5 mm, piezoelectric layer thickness of 30 µm, proof mass thickness of 4 mm, piezoelectric layer width of 0.12 mm, silicon nitride layer width of 0.16 mm, silicon nitride layer thickness of 30 µm, and proof mass material of aluminum. Eigen frequency analysis for the first six modes of operation for PMPG frequencies are: 1.2 HZ, 5.4 Hz, 6.9 Hz, 29,7 Hz, 694.8 Hz, 708.3 Hz. The first mode of operation is selected as operation mode and shows that 93 % of PMPG's total displacement and output power was produced in the range of 1---1.4 Hz, therefore PMPG can work when the heart rate between 60 and 84 bpm. Transient analysis performed at 1.2 Hz reaches the steady state before the first 10 cycles with output power density of 23.13 µW/cm3, which is suitable for powering cardiac pace maker.

Fabrication and characterization of vibration-driven AlN piezoelectric micropower generator compatible with complementary metal-oxide semiconductor process

This article describes the aluminum nitride (AlN)-based piezoelectric microgenerator for scavenging energy from ambient vibration. To achieve the low resonance frequency and maximize power density, a parametric study has been carried out by analytical modeling and finite element analysis. The piezoelectric microgenerator consists of AlN piezoelectric thin film with molybdenum (Mo) electrodes and silicon (Si) proof mass. The AlN was deposited on silicon-on-insulator wafer which is used as an insulating layer to defend the leakage current. The Mo electrode provides the excellent c-axis crystal growth of AlN. The fabricated AlN piezoelectric microgenerator can generate up to 6.4 nW at a frequency of 389 Hz and acceleration of 1.0 g (1 g = 9.81 m/s2). In addition, the output voltage and power density are 22.6 mVrms and 11.3 nW/mm3, respectively. The proposed generator is highly suitable for batch processing and has the possibility of harvesting energy from the ambient vibration.

A Low-Power Stand-Alone Adaptive Circuit for Harvesting Energy From a Piezoelectric Micropower Generator

An adaptive energy-harvesting circuit with low power dissipation is presented and demonstrated, which is useful for efficient ac/dc voltage conversion of a piezoelectric micropower generator. The circuit operates stand-alone, and it extracts the piezoelectric strain energy independent of the load and piezoelectric parameters without using any external sensor. The circuit consists of a voltage-doubler rectifier, a step-down switching converter, and an analog controller operating with a single supply voltage in the range of 2.5-15 V. The controller uses the piezoelectric voltage as a feedback and regulates the rectified voltage to adaptively improve the extracted power. The nonscalable power dissipation of the controller unit is less than 0.05 mW, and the efficiency of the circuit is about 60% for output power levels above 0.5 mW. Experimental verifications of the circuit show the following: 1) the circuit notably increases the extracted power from a piezoelectric element compared to a simple full-bridge diode rectifier without control circuitry, and 2) the efficiency of the circuit is dominantly determined by its switching converter. The simplicity of the circuit facilitates the development of efficient piezoelectric energy harvesters for low-power applications such as wireless sensors and portable devices.

Piezoelectric Micro-Power Generation Interface Circuits

New power conversion circuits to interface to a piezoelectric micro-power generator have been fabricated and tested. Circuit designs and measurement results are presented for a half-wave synchronous rectifier with voltage doubler, a full-wave synchronous rectifier and a passive full-wave rectifier circuit connected to the piezoelectric micro-power generator. The measured power efficiency of the synchronous rectifier and voltage doubler circuit fabricated in a 0.35-/spl mu/m CMOS process is 88% and the output power exceeds 2.5 /spl mu/W with a 100-k/spl Omega/, 100-nF load. The two full-wave rectifiers (passive and synchronous) were fabricated in a 0.25-/spl mu/m CMOS process. The measured peak power efficiency for the passive full-wave rectifier circuit is 66% with a 220-k/spl Omega/ load and supplies a peak output power of 16 /spl mu/W with a 68-k/spl Omega/ load. Although the active full-wave synchronous rectifier requires quiescent current for operation, it has a higher peak efficiency of 86% with an 82-k/spl Omega/ load, and also exhibits a higher peak power of 22 /spl mu/W with a 68-k/spl Omega/ load which is 37% higher than the passive full-wave rectifier.