Chan Ho Yang

Study on Application of Piezoelectricity to Korea Train eXpress (KTX)

In this study, we have investigated application of piezoelectricity to actual commercially operating high-speed Korean train. We recorded and analyzed the vibrations of commercial Korea Train eXpress (KTX). We experimented with different cantilever beam thicknesses (0.25 mm, 0.6 mm, and 1.0 mm) and different piezoelectric material dimensions (length × width × thickness, 10.0 mm × 10.0 mm × 0.5 mm, 20.0 mm × 10.0 mm × 0.5 mm, and 30.0 mm × 10.0 mm × 0.5 mm) on real data from recorded random frequencies and train vibration amplitudes. The addition of tip masses on the cantilever beam decreased the resonance frequency range when the vibrations were constant but not when they were random. The optimal condition was experimentally found, to involve decreasing the piezoelectric substrate beam thickness and increasing the piezoelectric substrate beam area rather than merely increasing the tip mass. The most effective method to improve the operational sensitivity was combination of decreasing the resonance frequency by adding tip masses, decreasing beam thicknesses, and increasing beam areas.

Restoration and Reinforcement Method for Damaged Piezoelectric Materials

This study investigated the effects of strain and crack formation on the performance of damaged piezoelectric materials as well as methods to restore damaged electrodes and reinforce the piezoelectric material. Specifically, this study investigated whether Ag paste (thickness: 0.1 mm) could restore electrical contact in damaged electrodes, and whether a coating of UV curable resin could provide reinforcement against crack formation. Experiments were conducted with a piezoelectric material on a steel cantilever substrate. The substrate was subjected to impact at various distances from the free end of the piezoelectric material to vary the applied strain. It was found that the output voltage increased with the strain (distance of impact from free end) until crack formation, which led to a large decrease in output. However, Ag paste could successfully restore electrical contact. Furthermore, before crack formation, coating with UV curable resin increased the maximum strain, and therefore, maximum electrical output, as well as cycle life.

Study on the Strain Effect of a Piezoelectric Energy Harvesting Module

In order to investigate the relationships among strain, frequency, and output power, a novel piezoelectric energy harvesting module with controllable strain was designed. Conventional vibration module can control over strain through variation in tip mass, but it is also affected by vibration frequency. In the contrast, the designed controllable strain module allows more accurate strain control at various frequencies through adjustment of the displacement of the free end of the cantilever from 5 mm to 45 mm. Experimental results proved that both types of modules exhibit an increase in open circuit output voltage with strain. But output voltage was decreased when the piezoelectric ceramic broke at severe strain. In addition, it was confirmed that the proposed module design can keep the strain constant, which allows investigation into the relationship between frequency and output power. At constant strain, the matching impedance was found to be low at high frequency. Thus, as effect of strain to the piezoelectric energy harvesting module, the optimum conditions for harvesting maximum power are found to be high frequency and the largest strain do not degrade the piezoelectric plate.

Design of Piezoelectric Energy Harvesting System by Magnetic Force–Controlled Resonance Frequency

We designed a piezoelectric energy harvesting system that can be controlled the resonance frequency to the frequency of external energy. A permanent magnet (10 mm × 10 mm × 5 mm) was affixed to the free end of cantilever, and a permanent magnet was affixed to each of the four faces of a rotor at 90° angles. The effect of the dimension of the permanent magnets (20 mm × 20 mm × 10 mm, 30 mm × 20 mm × 10 mm, and 40 mm × 20 mm × 10 mm) and the effect of the pole array (NNNN, SSSS, NSNS, and NNSS) were experimentally tested. The optimum conditions were selected by testing varied distances between the magnets at varied rpm. The experiments demonstrated that the maximum output voltage was generated for the largest magnet and the minimum distance. The most effective way to control the resonance frequency was to modify the pole arrays of magnets affixed to the rotor. Furthermore, the optimum conditions were determined at each distance by changing the pole array and rpm. Simulation software supports the experimental results.

Feasibility study on application of piezoelectricity to convert vibrations of Korea Train eXpress

In this study, we have investigated the feasibility of applying piezoelectricity to convert the mechanical vibrations of an operating commercial high-speed Korean train to useful electricity. We recorded and analyzed the vibrations of Korea Train eXpress (KTX). We experimented with different cantilever beam thicknesses (0.25, 0.6, and 1.0 mm) and different piezoelectric material dimensions (10.0 × 10.0 × 0.5 mm3, 20.0 × 10.0 × 0.5 mm3, and 30.0 × 10.0 × 0.5 mm3) on real data from recorded random frequencies and train vibration amplitudes. The addition of tip masses on the cantilever beam decreased the natural resonance frequency range when the vibrations were constant but not when they were random. The optimal condition was experimentally found, to involve decreasing the beam thickness and increasing the beam area rather than merely increasing the tip mass. The most effective method to improve the operational sensitivity was to decrease the resonance frequency by adding tip masses, decreasing beam thicknesses, and increasing beam areas.

Sustainable micro-power circuit for piezoelectric energy harvesting tile

ABSTRACT Piezoelectric energy harvesting tiles are used for converting the power of pedestrian footsteps in to electricity and can be used at the micro- and milli-watt level for storage and powering electronics devices. This paper effectively combines the systems and techniques for developing a sustainable circuit with the self-starting and self-power functions to efficiently store energy and drive low power consumption electronic devices from the piezoelectric energy harvester tile. The main part of the system is 80% efficient impedance matching converter with the self-starting and battery-less operation. The presented circuit has an overall efficiency of 63% and can power a wireless sensor node to transmit the information wirelessly.

Design of vibration exciter by using permanent magnets for application to piezoelectric energy harvesting

We designed a piezoelectric energy harvesting system that can shift the resonant frequency to match the fixed external energy frequency. A permanent magnet (10 × 10 × 5 mm3) was attached to the free end of a cantilever beam, and a permanent magnet was attached to each of the four faces of a rotor at 90° angles. The effect of the size of the permanent magnets (40 × 20 × 10 mm3, 30 × 20 × 10 mm3, and 20 × 20 × 10 mm3) and the effect of the pole array distribution (NNNN, SSSS, NSNS, and NNSS) were experimentally investigated. The optimum conditions were determined by testing various distances between the magnets at different rpms. The experiments showed that the maximum output power was generated for the minimum distance and largest magnet. The most effective approach to adjust the resonance frequency was to change the pole arrays of the magnets attached to the rotor. Furthermore, the optimum conditions were determined at each distance by changing the pole array and rpm. Software simulations support the experimental results.

Study on reinforcement and repair of cracked piezoelectric materials

This study investigated the effects of strain and crack formation on the performance of piezoelectric materials as well as methods to repair damaged electrodes and reinforce the piezoelectric material. Specifically, this study investigated whether Ag paste (thickness: 0.1 mm) could restore electrical contact in damaged electrodes, and whether a coating of UV curable resin could provide reinforcement against crack formation. Experiments were conducted with a piezoelectric material on a steel cantilever substrate. The substrate was subjected to impact at various distances from the free end of the piezoelectric material to vary the applied strain. It was found that the output voltage increased with the strain (distance of impact from free end) until crack formation, which led to a large decrease in output. However, Ag paste could successfully restore electrical contact. Furthermore, before crack formation, coating with UV curable resin increased the maximum strain, and therefore, maximum electrical output, as well as cycle life.

Development of impact-based piezoelectric road energy harvester for practical application

Many researches with regard to piezoelectric energy harvesting from pressure exerted by passing cars have been conducted. In this paper, an impact-based road energy harvester as buried-type is developed with the method that the piezoelectric device is deformed directly by the pressure due to passing cars. Based on this, the developed road energy harvester is made to the size of 30 × 30 × 9 cm3. The performance of this new road energy harvester is measured with UTM (Universal Testing Machine) and MMLS3 (Third-scale Model Mobile Load Simulator) which can apply loads similar to the actual traffic loads to the harvester in lab-scale. Finally, the buried harvester is experimented with APT (Accelerated Pavement Testing).

Designing a piezoelectric energy harvester using clicking mechanism

Many researches on developing new energy sources are being actively conducted recently. These new energy sources include renewable energy sources such as solar, wind, rain or wave energy and harvesting energy especially from human activities. In this research, we developed an energy harvester using human footsteps among various sources of energy. This energy harvester generates electricity by hitting and vibrating piezoelectric cantilever beams. It can be applied to stairs or sidewalks to produce electricity from human footsteps. We manufactured the energy harvester having a dimension of 200 × 200 × 160 mm3. There were four piezoelectric beams in the harvester. An experiment was conducted with a man pressing the harvester. When the harvester is pressed and released once, the hitting stick rotates 180°. We measured the output power caused by hitting and vibrating the piezoelectric beams. An impedance matching was conducted and the matched resistance turned out to be 1 kfí and at this value, the average voltage became 7.62 Vrms and the average power, 58.06 mWrms. The peak voltage was 18.44 Vpeak and the peak power was 340.03 mWpeak at the moment.