Measured Output Voltage Research Articles

Design and test of a novel two-body direct-drive wave energy converter

As a renewable energy, ocean wave energy is exploited with infinite potential to solve the energy crisis. In this study, we develop a novel two-body direct-drive wave energy converter (DD-WEC) to surmount the problems associated with low power density, low direct-drive speed of the buoys, seawater corrosion and maintenance in the existing two-body WEC. Its prototype consists of two cylindrical buoys that float horizontally at sea level and the Halbach permanent magnet linear generator (HPMLG) that is employed in the power take-off (PTO) system. The energy is extracted from the relative motion between two buoys oscillating. Compared with the existing WEC, the proposed WEC has more vigorous motion between buoys, higher conversion efficiency and little extra underwater structure, due to the utilization of the horizontal buoys and the HPMLG. First, the motion equations of buoys are derived on the basis of linear wave theory. And depending on the motion equations, the structure of buoys and the HPMLG is designed. And we found that compared with the existing WEC, the proposed WEC has more vigorous motion between buoys in the seawater waves oscillation. Then, based on finite-element method (FEM), the performance of the HPMLG is evaluated, and it can generate 19% more power than the traditional permanent magnet linear generator (TPMLG) based on the same wave motion. Finally, the DD-WEC prototype is manufactured based on the designed parameter. The manufactured prototype is tested in the test platform and the wave tank. The measured output voltage is highly consistent with the observed variation trends in FEM simulation data. The results show that the proposed DD-WEC is well suited for wave energy conversion.

Developing and Applying Chaotic Harris Hawks Optimization Technique for Extracting Parameters of Several Proton Exchange Membrane Fuel Cell Stacks

In this paper, an efficient optimization technique called Chaotic Harris Hawks optimization (CHHO) is proposed and applied for estimating the accurate operating parameters of proton exchange membrane fuel cell (PEMFC), which simulate and mimic its electrical performance. The conventional Harris Hawks optimization (HHO) is a recent optimization technique that is based on the hunting approach of Harris hawks. In this proposed optimization technique, ten chaotic functions are applied for tackling with the studied optimization problem. The CHHO is proposed to enhance the search capability of conventional HHO and avoid its trapping into local optima. The sum of squared errors (SSE) between the experimentally measured output voltage and the corresponding simulated ones is adopted as the objective function. The developed CHHO technique is tested on four various commercial PEMFC stacks to assess and validate its effectiveness compared with other well-known optimization techniques. A statistical study is performed to appreciate the stability and reliability of the proposed CHHO technique. However, the results show the effectiveness and superiority of proposed CHHO compared with the conventional HHO and other competitive metaheuristic optimization algorithms under the same study cases.

A High Performance Adaptive Digital LDO Regulator With Dithering and Dynamic Frequency Scaling for IoT Applications

In this paper, a high performance adaptive digital low-dropout voltage regulator (ADLDO) is proposed for Internet-of-Things (IoT) applications. In the proposed ADLDO, a fully synthesizable adaptive digital controller is designed. It automatically senses load variations and adaptively controls multi-loop architecture to reduce quiescent current, minimize output voltage ripples and achieve fast transient response. The multi-loop architecture with hill climbing reduces the total bi-directional shift registers length which results in the reduced leakage current in the transistor-switch-array (TSA), and improves the recovery time and output DC voltage accuracy. A dithering technique is introduced to eliminate the limit cycle oscillation (LCO) and improve the performance of the regulator. The dynamic frequency scaling (DFS) mechanism is proposed for reducing controller power consumption in steady state. In order to reduce the offset and output voltage error, a dynamic latch comparator is utilized. When the input supply voltage is varied from 0.5 V to 1 V, the measured output voltage ranges from 0.45 V to 0.95 V with 50 mV dropout voltage. The operating frequency is 10 MHz with fast transient response and quiescent current of 350 ns and 3.7μA, respectively. The maximum measured power and current efficiencies are 89.7 % and 99.97 %, respectively, with 1.9 mV output voltage ripples. Measured load and line regulations are 2.2 mV/mA and 9.5 mV/V respectively. The proposed circuit is implemented in 28 nm CMOS process and occupies 0.016 mm 2 chip area.

Universal finite-time observer based second-order sliding mode control for DC-DC buck converters with only output voltage measurement

DC-DC buck converters are widely used in industrial applications. Practically, there are parametric uncertainties, external disturbances and nonlinear unmodeled dynamics affecting the control performance of the DC-DC buck converters. Worse still, the current sensor may fail to work normally in practice. Taking the factors aforementioned into account, this paper proposes a universal finite-time observer (UFTO) based second-order sliding mode controller with only output voltage measurement in a simple structure for buck converters subject to mismatched disturbances. Firstly, a universal finite-time observer is designed to give the estimations of unmeasurable states including the current inductor and lumped disturbances. Secondly, introducing the estimations, a second-order sliding mode controller is proposed and a rigorous stability of the whole system is presented. Under the proposed finite-time controller, the system obtains a better convergence property and a better disturbance rejection ability comparing with the asymptotic control method. Moreover, the controller has a simple structure, providing convenience for engineers. As a by-product, only voltage sensor is needed, which reduces the cost and improves the fault tolerant ability for the system. Simulation and experimental results are investigated to validate the effectiveness of the proposed control approach.

Comparison of self-humidification effect on polymer electrolyte membrane fuel cell with anodic and cathodic exhaust gas recirculation

Self-humidification with anode/cathode recirculation was found to be an alternative in the place of external humidifier according to the previous studies in the last decade, however, there is still a lack of quantitative experimental and theoretical comparison between them. In this study, the dynamic PEM fuel cell system model with anodic and cathodic exhaust gas recirculation is proposed and related model calibration and verification are carried out by measured output voltage, gaseous pressure and mole concentration during the dynamic process. The model simulation shows quite good agreement with the experimental result and source of error is discussed. Based on developed model, it is simulated that the humidification effect is much better for cathode recirculation compared with anode recirculation, resulting in performance improvement, especially under the condition of low inlet RH. However, this improved humidification effect is weakened, considering the structure limit of recirculation pump and gas channel in this case. Besides, the power consumption of cathode recirculation pump is found to be much higher than that of anode recirculation. As a result, the anode recirculation is found to be a better solution considering the energy efficiency and mechanical structure limit. In contrast, cathode recirculation conducts better humidification effect, which is more suitable for the short-time low-inlet-humidity working conditions.

Energy harvesting from a novel contact-type dielectric elastomer generator

A novel contact-type (CT) dielectric elastomer generator (DEG), which can harvest energy from two dielectric elastomer membranes (DEMs) under a regular contact-type displacement excitation, is proposed and studied in this paper. The operating principle of the proposed CT DEG is introduced with its electrical outputs under a contact being derived. This is further verified by capacitance and output voltage measurement experiments, thus making the theoretical analysis credible. Furthermore, the energy harvesting (EH) performance of the CT DEG in simulated contact environments is fully investigated through the conducted numerical simulations, and the influences of the excitation parameters, the system structure parameters, the pre-stretched ratio of DEM and input voltage are studied. It was found that the system demonstrates a better EH performance under a larger amplitude and a smaller period of the excitation, and the system EH performance can be enhanced by increasing the plate’s radius, the pre-stretched ratio, the input voltage or decreasing the DEM’s radius. By adjusting these parameters appropriately, the system output voltage can be 10 times higher than the input voltage, and the system output power can be achieved as high as 22.94 mW under a given displacement excitation. The research results can provide some effective solutions for the design and improvement of the proposed CT DEG in contact-type energy harvesting.

Исследование линейных стабилизаторов напряжения на стойкость к воздействию специальных факторов

The paper deals with the issues of resistance of linear voltage stabilizers to the influence of special factors. The conducted researches are described, electric schemes at measurement of output voltage and current of chips are resulted. The calculated estimates of the resistance of linear voltage stabilizers to the influence of various special factors are also considered

Self-adhesive electrode applied to ZnO nanorod-based piezoelectric nanogenerators

ZnO nanorod-based piezoelectric devices have gained wide attention in energy harvesting systems as they can be processed at low temperatures onto flexible plastic substrates, giving a good potential for low cost. However, the vacuum-evaporated, precious metal contacts remain a high-cost element of the devices. This paper discusses the use of transparent conductive adhesives (TCAs) as an alternative top contact that is free from both vacuum-evaporation and precious metals. TCA films of various thicknesses were tape-cast onto nickel microgrid on PET substrates and adhered using low-pressure cold-lamination to bond the adhesive component of the TCA to piezoelectric generators with the final device structure of PET/ITO/ZnO-seed/ZnO-nanorods/CuSCN/PEDOT:PSS/TCA. The piezoelectric performances of the devices were compared by measuring output voltage in open-circuit and maximum power output across a range of resistive loads. The voltage output was observed to rise with increasing TCA thickness, reaching a maximum value of 0.72 V generated with 110 μm of TCA as top contact. However, the higher resistance due to increased TCA thickness led to decreased power output; a maximum calculated power of 0.25 μW was obtained from the device with the thinnest TCA layer of 22 μm. Finally, the performance of piezoelectric nanogenerators with TCA contacts were compared to a control device with an evaporated gold contact.

Four-plate capacitive power transfer system with different grounding connections

In this paper, a four-plate capacitive power transfer (CPT) system with different grounding connections is studied by taking the mutual coupling between the plates and the ground into consideration. A 4 * 4 mutual capacitance matrix model including the ground capacitances is established to accurately describe the coupling relationship between the four plates and the ground. Based on the proposed model, eight grounding connections are identified for effective power transfer among fifteen theoretically possible combinations. The electric field distribution and system output performance of a typical CPT system with two pairs of parallel plates are simulated for different grounding connections. A practical coupling setup consisting of two pairs of vertically placed parallel 300 mm * 300 mm square aluminum plates is built to verify the modeling and analysis. Both simulation and experimental results show the measured output voltage under different grounding connections are in good agreement with the theoretical results. It has been found that the ground has minimal impact on power transfer when one pair of the coupled transmitter and receiver plates are grounded, and the highest voltage gain and the lowest leakage electric field are also achieved under this grounding connection. However, considering the practicality, grounding one transmitter plate is the most suitable connection.

A Deep Learning Approach for Microwave and Millimeter-Wave Radiometer Calibration

Deep learning artificial neural network techniques can be applied for on-orbit calibration of microwave and millimeter-wave radiometer spaceborne instruments, including those for small satellites. The noise-wave model has been employed for noise characterization and validation of the proposed deep learning calibration technique for a synthetically generated Dicke-switching radiometer. The developed deep learning neural network radiometer calibrator produces high accuracy estimates of antenna temperatures from the measurements of radiometer output voltage and thermistor readings. Tests with noise-free and noisy samples of the developed model have shown that the proposed calibration method does not add any significant noise to the radiometer calibration. The performance of the proposed method does not degrade with increased nonlinearity for a radiometer, while nonlinearity is a challenging issue for conventional calibration techniques. The deep learning calibration model learns the radiometer noise characteristics from radiometer prelaunch measurements during thermal vacuum chamber testing. The neural network calibrator proposed in this paper has self-learning capability during the on-orbit operation of a radiometer that can be used to improve the performance of on-orbit calibration. The proposed technique is demonstrated by comparing the residual uncertainty of the deep learning calibration with the theoretical value. No numerical study is presented to compare the performance with conventional calibration techniques. The new method may be solely applied to calibrate the radiometer or applied along with conventional calibration techniques.

Dual active capacitive feedbacks for output capacitor-less low-dropout regulator

An output capacitor-less low-dropout (OCL-LDO) voltage regulator with dual active feedback paths is presented in this paper. The dual active feedbacks provide frequency compensation and spike voltage suppression. Two feedback loops are formed by capacitors Cc and Ca, respectively. The capacitor Ca path detects output voltage to suppress undershoot and overshoot during load transient. The frequency compensation is achieved by capacitor Cc, which helps the LDO regulator not only improve stability, but also enhance transient response without large current consumption. The total utilized capacitance values are only 1.5 pF. The proposed OCL-LDO was fabricated in 0.18 μm CMOS technology with supply voltage of 1.8 V. The LDO consumes 21 μA of quiescent current and the chip area is 0.47 mm × 0.49 mm. The measured output voltage difference is 90 mV when the load current is increased from 50 μA to 100 mA with CL= 100 pF and recovery time less than 1 μs. The power supply rejection is − 51.7 dB at 1 kHz.

Ultralow power voltage reference circuit for implantable devices in standard CMOS technology

SummaryAn ultralow power CMOS voltage reference for body implantable devices is presented in this paper. The circuit core consists of only regular threshold voltage PMOS transistors, thus leading to a very reduced output voltage dispersion, defined as σ/μ, and extremely low power consumption. A mathematical model of the generated reference voltage was obtained by solving circuit equations, and its numerical solution has been validated by extensive electrical simulations using a commercial circuit simulator. The proposed solution incorporates a passive RC low‐pass filter, to enhance power supply rejection (PSR) over a wide frequency range, and a speed‐up section, to accelerate the switching‐on of the circuit. The prototype was implemented in 0.18 μm standard CMOS technology and is able to operate with supply voltages ranging from 0.7 to 1.8 V providing a measured output voltage value of 584.2 mV at the target temperature of 36° C. The measured σ/μ dispersion of the reference voltage generated is 0.65% without the need of trimming. At the minimum supply of 0.7 V, the experimental power consumption is 64.5 pW, while the measured PSR is kept below –60 dB from DC up to the MHz frequency range.

Possibilities of the application magnetoelectric current sensor for the power supply in transport systems

The paper presents the review of the magnetoelectric current sensors. The possibility of output voltage measurement of the sensor in the function of DC magnetic field is also presented.

Enzyme-Functionalized Piezoresistive Hydrogel Biosensors for the Detection of Urea.

Urea is used in a wide variety of industrial applications such as the production of fertilizers. Furthermore, urea as a metabolic product is an important indicator in biomedical diagnostics. For these applications, reliable urea sensors are essential. In this work, we present a novel hydrogel-based biosensor for the detection of urea. The hydrolysis of urea by the enzyme urease leads to an alkaline pH change, which is detected with a pH-sensitive poly(acrylic acid-co-dimethylaminoethyl methacrylate) hydrogel. For this purpose, the enzyme is physically entrapped during polymerization. This enzyme-hydrogel system shows a large sensitivity in the range from 1 mmol/L up to 20 mmol/L urea with a high long-term stability over at least eight weeks. Furthermore, this urea-sensitive hydrogel is highly selective to urea in comparison to similar species like thiourea or N-methylurea. For sensory applications, the swelling pressure of this hydrogel system is transformed via a piezoresistive pressure sensor into a measurable output voltage. In this way, the basic principle of hydrogel-based piezoresistive urea biosensors was demonstrated.

Hole conductivity in the electrolyte of proton-conducting SOFC: Mathematical model and experimental investigation

Proton-conducting solid oxide fuel cell (SOFC) is promising for the intermediate and low temperature applications. The hole conductivity within the electrolyte has noticeable impact on the cell performance. In this article, a new model is proposed to evaluate the hole conductivity of the electrolyte directly. Single cells with different electrolyte thicknesses are fabricated to validate our model. The BaCe0.7Zr0.1Y0.2O3−δ electrolyte and Sm0.5Sr0.5CoO3−δ-Ce0.8Sm0.2O2−δ cathode is employed in our experiments. The predicted cell output capacities are in accord with both our experiments and the reported results, confirming that our proposed method is valid and effective. There are several distinct features of our model compared with previous reports: 1) Hole conductivity could be evaluated directly from the measured output voltages of the full cell, thus it simplifies the relevant experiment; 2) in order to make the cathode reaction model transferable among samples with diverse micro-structures, new parameters named TPB-specific exchange current density is proposed; and 3) for proton-conducting SOFC, an equivalent circuit model with the consideration of both electrolyte hole conductivity and various overpotentials is firstly proposed. Our model points out that the influence of the hole conductivity on the cell capacity could not be neglected in cases of relatively low output current, high temperature and thin membrane. Therefore the hole conductivity of the electrolyte must be taken into consideration in the related simulations.

Hydrogel-Based Sensors for Ethanol Detection in Alcoholic Beverages.

A fast and reliable determination of the ethanol concentration is essential in the analysis of alcoholic beverages. However, different factors like pH value or salt concentration can influence the ethanol measurement. Furthermore, analytical figures of merit for the alcohol sensor, such as limit of detection, sensitivity and measurement uncertainty, are necessary for the application. In this paper, a detailed sensor characterization of a novel sensor based on ethanol-sensitive poly acrylamide hydrogels will be presented. The resulting swelling pressure of the hydrogel was transformed via a piezoresistive pressure sensor into a measurable output voltage. These kinds of sensors can be used over a large measuring range, up to 50 vol% ethanol and more, with a high sensitivity. In the range from pH 7.4 to 4, the pH value had no influence on the sensor signal. Higher salt concentrations can slightly influence the measurement. The detection limit amounts to 0.06–0.65 vol% ethanol. The concentration of a vodka sample was determined with a sufficient measuring uncertainty.

Optimization of electricity production in a grid-tied solar power system with a three-phase quasi-Z-source inverter

Solar energy can be harnessed in all areas of the world and directly converted to electricity by means of photovoltaic (PV) systems. This leads to a reduced emission of greenhouse gases such as CO2. In this paper, a grid-tied quasi-Z-source inverter (qZSI) is considered with a PV array connected at the inverter input. The PV array is selected so as to ensure currents and voltages required by the qZSI. A novel maximum power point tracking (MPPT) algorithm, proposed in this study, does not require the measurement of the PV array current and does not oscillate around the maximum power point as opposed to most standard MPPT algorithms. The simulation model of the considered system was built in the MATLAB Simulink environment by using basic Simulink blocks only. The simulation analysis was performed with three PV array models of different complexity to establish the impact of the PV array dynamics on the overall system performance. The operation of the considered system was tested over a wide range of the solar irradiation levels and temperatures of the PV array. The proposed MPPT algorithm is additionally compared with the conventional constant-voltage algorithm, which also requires only measurement of the PV array output voltage. In the considered operating range, the proposed algorithm provides up to 453 W more power from the PV array (i.e., about 7% of the respective nominal power).

Piezoresistive Hydrogel-Based Sensors for the Detection of Ammonia.

Ammonia is an essential key compound in the chemical industry. However, excessively high ammonia concentrations can be harmful to the environment. Sensors for the detection of ammonia are therefore particularly important for environmental analysis. In this article, a novel hydrogel-based piezoresistive ammonia sensor is presented. In aqueous solution, ammonia reacts as a base. This alkaline pH change can be detected with stimuli-sensitive hydrogels. For such an application, highly sensitive hydrogels in the alkaline range with sufficient mechanical stability for the sensor application has to be developed. These conditions are fulfilled by the presented hydrogel system based on acrylic acid (AAc) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The hydrogel composition has a significant influence on the swelling behavior of the gel. Furthermore, the hydrogel swelling in ammonia solutions was tested and a detection limit in the range of 1 mmol/L ammonia depending on the buffer solution was determined. Ammonia-sensitive hydrogels can be used multiple times due to the repeatable swelling of the gel over several swelling cycles. To generate a measurable output voltage, the swelling pressure of ammonia-sensitive hydrogels were detected by using piezoresistive pressure sensors. All results of the free hydrogel swelling were verified in the sensor application. This low-cost ammonia sensor with a high sensitivity could be interesting for industrial chemical and biotechnological applications.

Study of coupling configurations of capacitive power transfer system with four metal plates

AbstractIn this paper, possible coupling configurations of a four-plate capacitive power transfer system are studied by varying the combinations of its input and output ports. A voltage source is applied between two of the four plates, and a load is connected to the other two to form different circuit topologies. A mathematical model based on a 4 × 4 mutual capacitance matrix is established for equidistantly placed four identical metal plates. Based on the proposed model, four separate circuit topologies are identified and analysed in detail and described in a general form. The electric field distributions of the coupling configurations are simulated by ANSYS Maxwell. The theoretical modeling and analysis are then verified by a practical system, in which four aluminum plates of 300 mm × 300 mm are used and placed with a gap of 10 mm between adjacent plates. The experimental results show that the measured output voltage and power under the four coupling configurations are in good agreement with the theoretical results. It has found that the voltage gain is the highest when the two inner plates are connected to the source, and this coupling configuration also has the lowest leakage electric field.

Dynamic Force Transducer Calibration Based on Electrostatic Force

Measurements of micro/nano dynamic force transducers (DFTs) in the micro-Newton range are of significant importance in many fields. In this paper, the electrostatic force in the micro-Newton range was used to generate dynamic force to calibrate the DFT, which is traceable to the International System of Units (SI). The relationship between the force input and voltage output of a DFT was investigated. The performance of DFT, such as resolution and reproducibility had been tested by the proposed method. The uncertainties, such as eccentric loading position, electrostatic force, output voltage measurement, and stiffness measurement, were estimated. The results showed that relative standard uncertainty in the determination of the calibration of the transducer was approximately 2.2%. This showed that the proposed system was very stable and repeatable.