Farid Ullah Khan

Copper foil-type vibration-based electromagnetic energy harvester

This paper presents the modeling, simulation, fabrication and experimental results of a vibration-based electromagnetic power generator (EMPG). A novel, low-cost, one-mask technique is used to fabricate the planar coils and the planar spring. This fabrication technique can provide an alternative for processes such as lithographie galvanoformung abformung (LIGA) or SU-8 molding and MEMS electroplating. Commercially available copper foils of 20 µm and 350 µm thicknesses are used for the planar coils and planar spring, respectively. The design with planar coils on either side of the magnets provides enhanced power generation for the same footprint of the device. The harvesters overall volume is 1 cm3. Excitation of the EMPG, at the fundamental frequency of 371 Hz, base acceleration of 13.5 g and base amplitude of 24.4 µm, yields an open circuit voltage of 60.1 mV, as well as 46.3 mV load voltage and 10.7 µW power for a 100 Ω load resistance. At a matching impedance of 7.5 Ω the device produced a maximum power of 23.56 µW and a power density of 23.56 µW cm−3. The simulations based on the analytical model of the device show good agreement with the experimental results.

State of the art in acoustic energy harvesting

For portable and embedded smart, wireless electronic systems, energy harvesting from the ambient energy sources has gained immense interest in recent years. Several ambient energies exist in the environment of wireless sensor nodes (WSNs) that include thermal, solar, vibration and acoustic energy. This paper presents the recent development in the field of acoustic energy harvesters (AEHs). AEHs convert the acoustic energy into useful electrical energy for the operation of autonomous wireless sensors. Mainly, two types of AEHs (electromagnetic and piezoelectric based) have been developed and reported in literature. The power produced by the reported piezoelectric AEHs ranges from 0.68 pW to 30 mW; however, the power generation of the developed electromagnetic AEHs is in the range of 1.5–1.96 mW. The overall size of most of the developed piezoelectric and electromagnetic AEHs are quite comparable and in millimeter scale. The resonant frequencies of electromagnetic AEHs are on the lower side (143–470 Hz), than that of piezoelectric AEHs (146 Hz–16.7 kHz).

Modeling and simulation of linear and nonlinear MEMS scale electromagnetic energy harvesters for random vibration environments.

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency.

State-of-the-art in vibration-based electrostatic energy harvesting

Recently, embedded systems and wireless sensor nodes have been gaining importance. For operating these devices several vibration-based energy harvesters have been successfully developed and reported, such as piezoelectric, electromagnetic, and electrostatic energy harvesters (EEHs). This paper presents the state-of-the-art in the field of vibration-based EEHs. Mainly, two types of EEHs, electret-free and electret-based, are reported in the literature. The developed EEHs are mostly of the centimeter scale. These energy harvesters, with resonant frequencies ranging from 2 Hz to 1.7 kHz, when subjected to excitation on the order of 0.25 g to 14.2 g, generate power that ranges from 0.46 nW to 2.1 mW.

Review of Energy Harvesters Utilizing Bridge Vibrations

For health monitoring of bridges, wireless acceleration sensor nodes (WASNs) are normally used. In bridge environment, several forms of energy are available for operating WASNs that include wind, solar, acoustic, and vibration energy. However, only bridge vibration has the tendency to be utilized for embedded WASNs application in bridge structures. This paper reports on the recent advancements in the area of vibration energy harvesters (VEHs) utilizing bridge oscillations. The bridge vibration is narrowband (1 to 40 Hz) with low acceleration levels (0.01 to 3.8 g). For utilization of bridge vibration, electromagnetic based vibration energy harvesters (EM-VEHs) and piezoelectric based vibration energy harvesters (PE-VEHs) have been developed. The power generation of the reported EM-VEHs is in the range from 0.7 to 1450000 μW. However, the power production by the developed PE-VEHs ranges from 0.6 to 7700 μW. The overall size of most of the bridge VEHs is quite comparable and is in mesoscale. The resonant frequencies of EM-VEHs are on the lower side (0.13 to 27 Hz) in comparison to PE-VEHs (1 to 120 Hz). The power densities reported for these bridge VEHs range from 0.01 to 9539.5 μW/cm3 and are quite enough to operate most of the commercial WASNs.

Experimental Study of Direct Laser Deposition of Ti-6Al-4V and Inconel 718 by Using Pulsed Parameters

Laser direct metal deposition (LDMD) has developed from a prototyping to a single metal manufacturing tool. Its potential for creating multimaterial and functionally graded structures is now beginning to be explored. This work is a first part of a study in which a single layer of Inconel 718 is deposited on Ti-6Al-4V substrate. Single layer tracks were built at a range of powder mass flow rates using a coaxial nozzle and 1.5 kW diode laser operating in both continuous and pulsed beam modes. This part of the study focused on the experimental findings during the deposition of Inconel 718 powder on Ti-6Al-4V substrate. Scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for characterization and phase identification. Residual stress measurement had been carried out to ascertain the effects of laser pulse parameters on the crack development during the deposition process.

Electromagnetic-based acoustic energy harvester

The development of an electromagnetic-based acoustic energy harvester using Helmholtz resonator is reported in this paper. The working principle, fabrication and characterization of the harvester are discussed. The developed harvester comprises of an orifice, cavity, flexible membrane, moving magnets and a fixed wound coil. The harvester is characterized under acoustic energy at different sound pressure levels (SPLs) and is subjected to both forward frequency sweep (FFS) and reverse frequency sweep (RFS). At resonance and under 125 dB SPL, the harvester produced a maximum open circuit rms voltage of 667 mV. However, when connected to an optimum load of 52 ohm, it generated an rms load voltage of 319.8 mV. At resonance and when subjected to 125 dB SPL the maximum power of 1966.77 μW is delivered to the load, that leads to a maximum power density of 133.6 μW/cm3 for the developed harvester.

Vibration-based electromagnetic type energy harvester for bridge monitoring sensor application

Fabrication and experimentation of vibration-based electromagnetic energy harvester is reported in this research paper. Energy harvester with both planar and wound coils have been developed and characterized under sinusoidal excitation. Energy harvester consists of two permanent magnets residing on a Latex membrane, two double sided PCB fabricated planar coils, Teflon spacers for providing gap between the permanent magnets and planar coils, and wound coils mounted on sides of Teflon spacers. When the harvester is subjected to vibration, due to the relative movement between the magnets and coils, the coils experience the change in magnetic flux density which causes an emf to generate at the coils terminals. Energy harvester has a dimension of 18 mm × 18 mm. Prototype has been characterized under sinusoidal excitation and are subjected to frequency sweep from 10 to 80 Hz at acceleration levels of 0.3 g, 0.5 g, 1 g, 2 g and 3 g. Single planar and wound coil of prototype generates an open circuit voltage of 15.7 mV and 11.05 mV respectively at 3 g and at resonant frequency 27 Hz. When excited at resonance and 3 g base acceleration a load power of 1.8 μW and 2.1 μW is obtained from single planar and wound coil respectively under matching impedance conditions for prototype.

Vibration-Based Electromagnetic Energy Harvester

This paper presents the simulation, fabrication, and experimental results of a vibration-based electromagnetic power (EMPG) generator. A novel, low cost, one mask technique is used to fabricate the planar coils and the planar spring. This fabrication technique can provide an alternative for processes such as Lithographie Galvanoformung Abformung (LIGA) or SU-8 molding and MEMS electroplating. Commercially available copper foils of 20 μm and 350 μm thicknesses are used for the planar coils and planar spring, respectively. The design with planar coils on either side of the magnets provides enhanced power generation for the same footprint of the device. The device overall size is 1 cm3 . Simulations of the modal analysis of the spring-mass system and the magnetostatic analysis of the magnetic field generated by the magnets are performed with COMSOL multiphysics®. Excitation of the EMPG at the fundamental frequency of 371 Hz and at 13.5 g base acceleration (base amplitude 24.4 μm) yields an open circuit voltage of 60.1 mV, as well as 46.3 mV load voltage and 10.7 μW power for a 100 Ω load resistance. At matching impedance of 7.5 Ω the device produced a maximum power of 23.56 μW and a power density of 23.56 μW/cm3 .Copyright

An improved design of Helmholtz resonator for acoustic energy harvesting devices

Helmholtz resonator (HR) is the key element of acoustic energy harvesting devices. It is used to augment or attenuate the incoming acoustic wave. In acoustic energy harvesters the objective of HR is to augment the incoming acoustic wave. In this work an improved architecture of HR is proposed for acoustic energy harvesting devices. Modeling and simulation of the HR is reported. The HR is modeled as one degree of freedom system. The proposed HR has a high pressure gain as compared to the HR used in previously developed acoustic energy harvesting devices. The proposed design for HR results in high acoustic stiffness of the air entrapped inside the Helmholtz cavity that ultimately improves the pressure gain of the HR. Moreover, for similar dimensions the resonant frequency of the proposed HR is 1693 Hz, while resonant frequency of the reported HRs is 1119.7 Hz. Furthermore, at resonance the pressure gain of the proposed HR is 56.5 dB which is quite high than the pressure gain of the reported HRs with cylindrical shape cavities that is 52.7 dB.