Formal Chaos Existing Conditions on a Transmission Line Circuit with a Piecewise Linear Resistor

By using one-dimensional (1-D) map methods, some lossless transmission line circuits with a short at one side terminal have been actively studied. Bifurcation results or chaotic states in the circuits have been reported. On the other hand, many weak or strong definitions such that a 1-D map is mathematically chaotic are still being studied. In such definitions, the definition of formal chaos is well known as being the most traditional and most definite. However, formal chaos existences have not been rigorously proven in such circuits. In this paper, a general lossless transmission circuit is considered first with a dc bias voltage source in series with a load resistor at one side terminal and with a three-segment piecewise linear resistor at another side terminal. Secondly, the method for deriving a 1-D map describing the behavior of the circuit is summarized. Thirdly, to provide a basis of chaotic application for the 1-D map, the mathematical definition of formal chaos and the sufficient conditions of the existence of formal chaos are discussed. Furthermore, by using Maple, formal chaos existences and bifurcation behavior of 1-D maps are presented. By using the Lyapunov exponent, the observability of formal chaos in such bifurcation processes is outlined. Finally, the principal results and the future works are summarized.

Exploration of 2D Ti3C2 MXene for all solution processed piezoelectric nanogenerator applications

A new 2D titanium carbide (Ti3C2), a low dimensional material of the MXene family has attracted remarkable interest in several electronic applications, but its unique structure and novel properties are still less explored in piezoelectric energy harvesters. Herein, a systematic study has been conducted to examine the role of Ti3C2 multilayers when it is incorporated in the piezoelectric polymer host. The 0.03 g/L of Ti3C2 has been identified as the most appropriate concentration to ensure the optimum performance of the fabricated device with a generated output voltage of about 6.0 V. The probable reasons might be due to the uniformity of nanofiller distribution in the polyvinylidene difluoride (PVDF) and the incorporation of Ti3C2 in a polymer matrix is found to enhance the β-phase of PVDF and diminish the undesired α-phase configuration. Low tapping frequency and force were demonstrated to scavenge electrical energy from abundant mechanical energy resources particularly human motion and environmental stimuli. The fabricated device attained a power density of 14 µW.cm−2 at 10.8 MΩ of load resistor which is considerably high among 2D material-based piezoelectric nanogenerators. The device has also shown stable electrical performance for up to 4 weeks and is practically able to store energy in a capacitor and light up a LED. Hence, the Ti3C2-based piezoelectric nanogenerator suggests the potential to realize the energy harvesting application for low-power electronic devices.

Rancang Bangun DC Chopper Satu Kuadran Berbasis Simulink Matlab

Catu daya DC merupakan serangkaian komponen elektronik yang dapat menyuplai tegangan DC ke komponen elektronik lainnya. Setiap perangkat elektronik membutuhkan tegangan suplay yang berbeda-beda. Karena penggunaan catu daya yang luas ini, diperlukan suatu sistem yang dapat mengkonversikan tegangan DC dari suatu tingkat tegangan ketingkat tegangan lainnya. Maka salah satu cara untuk mengubah tegangan DC ketegangan DC lainnya digunakan sistem yang dikenal sebagai DC choper. Pada Sistem DC choper satu kuadran nilai rata-rata tegangan keluaran dan arusnya selalu positif dan dayanya selalu mengalir dari sumber ke beban. Paper ini mengusulkan DC chopper satu kuadran berbasis kontroller proportional (P). Sistem kendali diimplementasikan dengan menggunakan mikrokontroller arduino mega 2560 yang diprogram dengan simulink matlab. Peralatan sistem kendali dilengkapi dengan potensiometer sebagai penurunan tegangan input 200 VDC menjadi tegangan yang bervariasi sesuai dengan yang diinginkan yang diinginkan agar tegangan keluaran tetap stabil. Tegangan 200 VDC yang termasuk tegangan tinggi maka dibutuhkan IGBT untuk membuat arus yang lebih besar dan beroperasi dalam tegangan tinggi karena memiliki efesiensi yang lebih baik. Untuk mendeteksi tegangan tersebut dibutuhkan sensor tegangan yang terdiri dua buah resistor yang bernilai 330K dan 6,3K dan sensor arus yang digunakan unyuk mendeteksi arus, sensor arus yang digunakan sensor arus ACS712. Sistem DC choper satu kuadran diverifikasikan melalui percobaan di laboratorium dengan beban load resistor. Hasil pengujian menunjukkan bahwaDC chopper satu kuadran berbasis kontroller proportional yang diusulkan dalam paper ini telah bekerja dengan baik. Hal ini dapat dilihat dari tegangan output yang dihasilkan sesuai dengan tegangan yang diinginkan yang atur melalui pontesiometer.

Analysis, Simulation, and Development of a Low-Cost Fully Active-Electrode Bioimpedance Measurement Module

A low-cost 1 kHz–400 kHz operating frequency fully-active electrode bioimpedance measurement module, based on Howland current source, is presented in this paper. It includes a buffered positive feedback Howland current source, implemented with operational amplifiers, as well as an AD8421 instrumentation amplifier, for the differential voltage measurements. Each active electrode module can be connected to others, assembling a wearable active electrode module array. From this array, 2 electrodes can be selected to be driven from a THS413 fully differential amplifier, activating a mirrored Howland current source. This work performs a complete circuit analysis, verified with MATLAB and SPICE simulations of the current source’s transconductance and output impedance over the frequency range between 1 kHz and 1 MHz. Resistors’ tolerances, possible mismatches, and the operational amplifiers’ non-idealities are considered in both the analysis and simulations. A comparison study between four selected operational amplifiers (ADA4622, OPA2210, AD8034, and AD8672) is additionally performed. The module is also hardware-implemented and tested in the lab for all four operational amplifiers and the transconductance is measured for load resistors of 150 Ω, 660 Ω, and 1200 Ω. Measurements showed that, using the AD8034 operational amplifier, the current source’s transconductance remains constant for frequencies up to 400 KHz for a 150 Ω load and 250 kHz for a 1200 Ω load, while lower performance is achieved with the other 3 operational amplifiers. Finally, transient simulations and measurements are performed at the AD8421 output for bipolar measurements on the 3 aforementioned load resistor values.

Analytical model and energy harvesting analysis of a vibrating slender rod with added tip mass in three-dimensional space

In the paper, a new 3D energy harvesting system is provided. This work discussed the Lagrange approach to derive the differential equations of motion in the case of energy harvesting systems. An electromechanical system consists of a mechanical resonator, a piezoelectric transducer and electrical circuit with the load resistor. A flexible slender rod clamped at the bottom and loaded by the tip mass is proposed as the resonator. Moving in the 3D space, it enables the system to avoid the gravitational potential barrier of the straight vertical shape in case of buckling. This paper investigates the response of the rod deflection and the root mean square power output of selected vibration mode shapes with an attached tip mass.

Stochastic Thermodynamics of a Piezoelectric Energy Harvester Model

We experimentally study a piezoelectric energy harvester driven by broadband random vibrations. We show that a linear model, consisting of an underdamped Langevin equation for the dynamics of the tip mass, electromechanically coupled with a capacitor and a load resistor, can accurately describe the experimental data. In particular, the theoretical model allows us to define fluctuating currents and to study the stochastic thermodynamics of the system, with focus on the distribution of the extracted work over different time intervals. Our analytical and numerical analysis of the linear model is succesfully compared to the experiments.

Symmetry and asymmetry from MEMS variable capacitor by nonlinear micro stoppers

Mechanical stoppers in MEMS capacitive systems can dramatically affect electrical performances and result in complicated mechanical dynamic responses. This paper introduces electromechanical coupling nonlinear dynamic responses in MEMS variable dual-capacitor with an effect of nonlinear and asymmetrical stoppers. We found that the capacitance in the electrical circuit system related to the first-order derivative of the output voltage on a load resistor, and the variable dual-capacitor was strongly affected by the coupling of up and down superposition instantaneous electrostatic force and limited space by the length of nonlinear stoppers. The numerical calculation results and the experimental results in our analysis based on our system had a good agreement, and the numerical simulation results presented rich nonlinear impacts dynamic responses through the imposed voltage and the height of stoppers in MEMS variable dual-capacitive device. The device in operation cannot reach the 0.6 time's initial gap due to small forcing amplitude (1.026 g). However, we observed that the movable plate and stoppers (across the 0.6 time's initial gap) had fierce impacts due to big forcing amplitude (4 g) on to the device. With asymmetric stopper each impact, we also concluded that the movable plate would experience attenuations of the displacement until the moment to the next impacts. Moreover, the height of stoppers can not only result in complicated dynamic motion of the movable plate, but also can modulate a voltage of the fixed plate with its asymmetry structure.

Effect of Electromechanical Coupling on Locally Resonant Metastructures for Simultaneous Energy Harvesting and Vibration Attenuation Applications

The study of simultaneous energy harvesting and vibration attenuation has recently been the focus in many acoustic meta-materials investigations. The studies have reported the possibility of harvesting electric power using electromechanical coupling; however, the effect of the electromechanical resonator on the obtained bandgap’s boundaries has not been explored yet. In this paper, we investigate metamaterial coupled to electromechanical resonators to demonstrate the effect of electromechanical coupling on the wave propagation analytically and experimentally. The electromechanical resonator is shunted to an external load resistor to harvest energy. We derive the analytical dispersion curve of the system and show the band structure for different load resistors and electromechanical coupling coefficients. To verify the analytical dispersion relations, we also simulate the system numerically. Furthermore, experiment is carried out to validate the analytical observations. The obtained observations can guide designers in selecting electromechanical resonator parameters for effective energy harvesting from meta-materials.

The construction and testing of an acoustic energy harvester consisting of a Helmholtz resonator and a loudspeaker

Sound energy is all around but not properly utilized despite being a source of electricity. This research was conducted to construct and test an acoustic energy harvester consisting of a Helmholtz resonator and a loudspeaker. The resonator cavity was made of 10 mm-thick cube-shaped acrylic plates with an inner side length of 300 mm while its neck was made of PVC (polyvinyl chloride) pipes with an inner diameter of 55 mm and three length variations at 50 mm, 70 mm, and 90 mm. A 6-inch subwoofer loudspeaker was mounted on the resonator back wall facing the cavity with its terminals connected to a 100-ohm load resistor. The sound waves entering the resonator cavity through the neck were converted into the alternating electric current flowing through the resistor. The test was conducted experimentally by exposing the harvester to sound waves at a maximum sound pressure level (SPL) of 100 dB and frequency variations from 25 Hz to 200 Hz. The root-mean-square (rms) voltages across the resistor were measured to calculate the output rms values for electric power. The results showed seven spectrum peaks which appeared at frequencies of 31 Hz, 37 Hz, 41 Hz, 49 Hz, 58 Hz, 73 Hz, and 82 Hz. Moreover, a shorter neck was also observed to have produced higher output power as indicated by the highest value of 2.75 mW obtained by using a 50 mm-long resonator neck at 37 Hz frequency and 100 dB SPL. These findings showed the acoustic energy harvester used to be effective due to its ability to produce electricity even at low frequencies below 100 Hz.