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This article proposes a triple-mode isolated resonant buck–boost converter over a wide input voltage range for residential applications of photovoltaic arrays and fuel cells. First, in case that the input voltage is smaller than the nominal voltage, it operates in a resonant-boost mode that boosts the input voltage by using a bridgeless structure on the secondary-side. Next, if the input voltage is within the range of the nominal voltage, it operates in a fully series-resonant mode, which results in high efficiency by the soft-switching on the primary-side switches and reduced conduction loss. Last, if the input voltage is more than the nominal voltage, it operates in a pulsewidth modulation series-resonant buck mode, which can achieve the step-down conversion by reducing the duty cycle. Unlike the conventional resonant converters, the proposed converter achieves high efficiency and less number of power components over a wide input voltage range. Finally, the performance of the proposed triple-mode isolated resonant converter has been fully verified on a prototype 400 W test-bed in the wide input voltage of 35–65 V.

This paper investigates a robust model reference adaptive control (MRAC) method for a three-phase constant-voltage constant-frequency (CVCF) inverter with an output LC filter. The proposed MRAC method is designed to stabilize the error dynamics of the system by a feedback control term in the steady state and attenuate the parameter uncertainties of the system by an updated MRAC term. Unlike the conventional proportional–derivative control (PDC) scheme, the proposed MRAC scheme ensures the fast convergence of the output errors to the exponential trajectories predefined by the reference models. Furthermore, the adaptive state-feedback mechanism can guarantee the fast dynamic response in the transient state without using load current sensors or observers. The asymptotic stability is mathematically proven by a Lyapunov theory. The feasibility of the proposed controller is confirmed through extensive experimental studies on a prototype three-phase CVCF inverter with a TI TMS320LF28335 DSP. Finally, comparative experimental results of three control methods (i.e., conventional PDC, feedback linearization control, and proposed MRAC) are provided to validate the superior performance of the proposed method such as fast transient response, low total harmonic distortion, and robustness to parameter uncertainties under critical load conditions (i.e., abrupt load changes, unbalanced loads, and distorted nonlinear loads).

This letter presents a high-gain energy-efficient three-stage amplifier, which employs buffering-based pole relocation and dual-path structure. The proposed design does not rely on the introduction of compensation zero and preserves the unity-gain bandwidth (GBW) of the local feedback loop (LFL). Compared to the topologies using active-zero insertion, the 3rd pole is formed with a much smaller capacitance (parasitic capacitance), enabling it to be placed at a significantly higher frequency while consuming lower power. Moreover, the parasitic pole at the main path is bypassed by using an auxiliary path. Thus, the 3rd pole can be pushed to a higher frequency more easily than the topologies using an active zero. As a result, the GBW of the LFL in the proposed work is less limited. The proposed design improves the state-of-the-art FOM L by 36%, LC-FOM S by 26%, and LC-FOM L by 218%, while preserving robustness of the performance.

The effect of the swirl clocking on three-dimensional nozzle guide vane (NGV) is investigated using computational fluid dynamics. The research reports the loss characteristics of leaned and swept NGVs and the influence of swirl clocking. The three-dimensional NGVs are built by stacking the same 2D profile along different linear axes, characterized by different angles with respect to the normal or radial direction: ε = −12° ~ +12° for the leaned and γ = −5° ~ +10° for the swept airfoils. A total of 40 models are analyzed to study the effects of lean and sweep on aerodynamic performance. To investigate the influence of swirl clocking, the analysis cases include the center of the swirl that was positioned at the leading edge as well as the middle of the passage. The prediction results show that the relationship of the changes in mass flow rate and throat area are not monotonic. Further observation confirms the redistribution of loading and flow angle under different lean and sweep angles, thus, three-dimensional design is a key influencing factor on aerodynamic performance. In the presence of swirl clocking, NGV performance is changed significantly and the findings offer new insight and opportunities to improve three-dimensional NGV airfoil design.

Nanostructured materials synthesized by the hydrothermal and thermal reduction process were tested to detect the dimethyl methylphosphonate (DMMP) as a simulant for chemical warfare agents. Manganese oxide nitrogen-doped graphene oxide with polypyrrole (MnO2@NGO/PPy) exhibited the sensitivity of 51 Hz for 25 ppm of DMMP and showed the selectivity of 1.26 Hz/ppm. Nitrogen-doped multi-walled carbon nanotube (N-MWCNT) demonstrated good linearity with a correlation coefficient of 0.997. A comparison between a surface acoustic wave and quartz crystal microbalance sensor exhibited more than 100-times higher sensitivity of SAW sensor than QCM sensor.

This paper proposes a variable structure speed controller (VSSC) that guarantees the robust transient performance against the external disturbances and parameter uncertainties of an interior permanent magnet synchronous motor (IPMSM) drive. Unlike the conventional VSSC applied to the IPMSMs, the proposed nonlinear compensating control term not only assures the robustness against the system uncertainties, but also implements the maximum torque per ampere technique. Furthermore, the convergence and stability of the proposed VSSC are fully proven through the Lyapunov theory by introducing reasonable bounded uncertainties which determine a feasible range for the system dynamics. The effectiveness of the proposed scheme is investigated through the simulation using MATLAB/Simulink and experiment using a prototype IPMSM drive system with a TI TMS320F28335 DSP. Finally, the proposed VSSC can ensure faster and more robust transient response than the conventional proportional-integral speed controller under the dynamic load conditions including the uncertainties.

We report a schlieren-style stroboscopic phase-contrast field-amplitude imaging of two-dimensional acoustic whispering gallery modes in a circular shell cavity immersed in liquid. A schlieren signal is combined with a presplit reference beam to enable nonscan field-amplitude imaging. Excitation mechanisms of standing and traveling eigenmodes, respectively, are analyzed with acoustic ray simulations presented in a Poincaré surface of sections. The time evolutions for both standing and traveling eigenmodes are reconstructed using the stroboscopic capability.

This paper proposes a fuzzy model predictive direct torque control (FMP-DTC) strategy of interior permanent magnet synchronous motors (IPMSMs) for electric vehicle (EV) applications. The fuzzy logic control technique incorporated into the proposed FMP-DTC scheme dynamically determines the appropriate values of the weighting factors, and then generates the optimal switching states that minimize the electromagnetic torque and stator flux errors. Unlike the conventional model predictive (MP)-DTC strategy, the optimal switching states of the proposed FMP-DTC are selected without retuning the weighting factors. It means that they are updated depending on the specific operating conditions. Therefore, the proposed FMP-DTC is effective in various operating conditions that make it suitable for the EV-traction operating environment. Hence, the proposed FMP-DTC method has a simple control structure and can explicitly handle the system constraints. The performance evaluation is carried out via both MATLAB/Simulink and a prototype IPMSM test-bed with a TMS320F28335 digital signal processor (DSP). Comparative simulation and experimental results present the evidence of the performance improvements based on the proposed FMP-DTC strategy compared with the conventional MP-DTC strategy by indicating a fast transient torque response, low ripples, and an accurate speed tracking even under rapid climbing or emergency braking situations.

This paper proposes an online identification method that can accurately estimate the stator resistance and dq -axis stator inductances for the effective model-based sensorless control of interior permanent magnet synchronous motors (IPMSMs). The proposed affine projection algorithms are uniquely designed in the estimated rotating γ-δ frame to precisely identify the parameters mentioned above. The two time-scale approaches are employed in the affine projection algorithms to estimate the three electrical parameters. Despite the electrical parameter variations due to the temperature change and magnetic saturation during operation, the rich enough data are provided to the affine projection algorithms in the discrete-time domain to accurately retrieve the updated parameters. These correctly estimated parameters are adapted to the extended back electromotive force observer for the sensorless control of IPMSM drives. Hence, the adaptation of online updated parameters makes the observer stable and robust to parameter variations as compared to the conventional observer without updated parameters. The MATLAB/Simulink-based simulation results and experimental results via a prototype IPMSM test-bed having TMS320F28335 DSP are given to verify the accurate convergence of the estimated parameters, which results into a stable sensorless control system under various operating conditions.

G nerve agents are colorless, odorless, and lethal chemical warfare agents (CWAs). The threat of CWAs, which cause critical damage to humans, continues to exist, e.g., in warfare or terrorist attacks. Therefore, it is important to be able to detect these agents rapidly and with a high degree of sensitivity. In this study, a surface acoustic wave (SAW) array device with three SAW sensors coated with different sensing materials and one uncoated sensor was tested to determine the most suitable material for the detection of nerve agents and related simulants. The three materials used were polyhedral oligomeric silsesquioxane (POSS), 1-benzyl-3-phenylthiourea (TU-1), and 1-ethyl-3-(4-fluorobenzyl) thiourea (TU-2). The SAW sensor coated with the POSS-based polymer showed the highest sensitivity and the fastest response time at concentrations below the median lethal concentration (LCt50) for tabun (GA) and sarin (GB). Also, it maintained good performance over the 180 days of exposure tests for dimethyl methylphosphonate (DMMP). A comparison of the sensitivities of analyte vapors also confirmed that the sensitivity for DMMP was similar to that for GB. Considering that DMMP is a simulant which physically and chemically resembles GB, the sensitivity to a real agent of the sensor coated with POSS could be predicted. Therefore, POSS, which has strong hydrogen bond acid properties and which showed similar reaction characteristics between the simulant and the nerve agent, can be considered a suitable material for nerve agent detection.

This paper presents a reconfigurable time-to-digital converter (TDC) used to quantize the phase of the impedance in electrical impedance spectroscopy (EIS). The TDC in the EIS system must handle a wide input-time range for analysis in the low-frequency range and have a high resolution for analysis in the high-frequency range. The proposed TDC adopts a coarse counter to support a wide input-time range and cascaded time interpolators to improve the time resolution in the high-frequency analysis without increasing the counting clock speed. When the same large interpolation factor is adopted, the cascaded time interpolators have shorter measurement time and smaller chip area than a single-stage time interpolator. A reconfigurable time interpolation factor is adopted to maintain the phase resolution with reasonable measurement time. The fabricated TDC has a peak-to-peak phase error of less than 0.72&deg, over the input frequency range from 1 kHz to 512 kHz and the phase error of less than 2.70&deg, when the range is extended to 2.048 MHz, which demonstrates a competitive performance when compared with previously reported designs.