Active Vibration Isolation System (AVIS) using a Voice Coil Actuator to improve Free Space Optics Communication

In Free Space Optic communication (FSOC), transmitter and receiver's alignment is vital to maintain the line of sight during the whole communication period. This is critical in data transmission over a long-distance. Vibration at either receiver or transmitter, causes misalignment and this affects FSOC. In this paper, AVIS, which can actively isolate FSO devices from low-frequency vibration from the ground, is designed and developed. The main goal is to reduce vibration from the top plate of the system where the telescope of the FSOC system is placed. An analytical model of the active vibration isolation is derived, and then the real prototype is fabricated. An imbalance mass system is used as an exciter for the system. Furthermore, for the cost-saving factor, a voice coil actuator which is modified from a conventional loudspeaker is used as an actuator for the system. LQR controller is implemented by using LabVIEW. The results show that the displacement level of the system with excitation frequencies 6 Hz, 12 Hz and 18 Hz are reduced more than 85 %. Moreover, it is proven that the loudspeaker not only costs lower but also gives a good performance for an AVIS. - 2019 IEEE.Scopu

Vibration Energy Harvesting using Single and Comb-shaped Piezoelectric Beam Structures: Modeling and Simulation

AbstractOf late, many have shown great interests in the area of energy harvesting or energy scavenging. Researchers have been venturing into methods that can generate acceptable level of voltage since decades ago. In line with the spirit of green technology, energy harvesting will be a major contributor towards saving our environment in near future. Vibration energy harvesting, specifically, is getting more and more attention nowadays. With the abundant sources, this type of energy harvesting can generate desired voltage to power any low power devices and wireless sensor; and subsequently high power devices in the future. In this research, unimorph piezoelectric energy harvester is chosen to harvest wideband mechanical energy. The derivation of the mathematical modelling is based on the Euler-Bernoulli beam theory. MATLAB and COMSOL Multiphysics software are used to study the influence of the structure in generating output voltage due to base excitations. Finally, the results of the frequency response are displayed in the form of voltage within frequency range of 0 to 3500Hz, at which the comb-shaped piezoelectric beam structure shows better performance as there exist more natural frequencies in the specified range of frequency

Voltage Generation in Piezoelectric Energy Harvesting with Magnet: FEA Simulation and Experimental Analysis

Energy harvesting devices are needed as an alternative to batteries as it is costly to power up wireless sensor network. However, the power generated and operating bandwidth for the typical energy harvester are still compromised. Therefore, in this work, the use of permanent magnet in Piezoelectric Energy Harvester (PEH) is proposed to increase the operating bandwidth. A simulation study was conducted using COMSOL Multiphysics software to observe the effect of mechanical tuning using magnet on the voltage produced. It shows that PEH with oscillating magnetic field is capable of reaching generated peak power of 0.775 mW and increase the operating bandwidth by 10%. Experimental setup was also fabricated to further validate the observation at different polarities and varying distances with permanent magnets. It is observed that while the peak power achieved in the attractive mode is smaller as compared to its counterpart, however, its bandwidth is larger

Adaptivni elektromagnetni blažilnik vibracij za večmodalne konstrukcije

All structures experience vibrations due to external dynamic force excitations, such as earthquakes and wind loadings. At resonance, the impact of this natural dynamic force on structures may lead to structural failures. Hence, an absorber is mounted to absorb vibrations from the primary system. Unfortunately, passive tuned mass absorbers can only target a single frequency. Since structural buildings possess multiple modes, an adaptive or tune-able vibration absorber is needed to attenuate the vibration in a multi-degree of freedom (MDOF) system. In this work, an adaptive electromagnetic vibration absorber (AEMVA) is proposed to eliminate the effects of vibrations and is dynamically tuned using electromagnets. By varying the current supplied to the coil, the stiffness of the AEMVA can be adjusted, resulting in a varying absorber frequency. A mathematical description of the AEMVA on a three-story prototype model building is also presented. The three-story benchmark model was used to demonstrate the effectiveness of AEMVA in absorbing multiple vibration modes, both analytically and experimentally. It is shown that 68.81 %, 50.49 %, and 33.45 % of vibration amplitude reductions were achieved at the first, second, and third modes, respectively