Showing papers on "Sine wave published in 2021"

A four-state adaptive Hopf oscillator.

Abstract: Adaptive oscillators (AOs) are nonlinear oscillators with plastic states that encode information. Here, an analog implementation of a four-state adaptive oscillator, including design, fabrication, and verification through hardware measurement, is presented. The result is an oscillator that can learn the frequency and amplitude of an external stimulus over a large range. Notably, the adaptive oscillator learns parameters of external stimuli through its ability to completely synchronize without using any pre- or post-processing methods. Previously, Hopf oscillators have been built as two-state (a regular Hopf oscillator) and three-state (a Hopf oscillator with adaptive frequency) systems via VLSI and FPGA designs. Building on these important implementations, a continuous-time, analog circuit implementation of a Hopf oscillator with adaptive frequency and amplitude is achieved. The hardware measurements and SPICE simulation show good agreement. To demonstrate some of its functionality, the circuit’s response to several complex waveforms, including the response of a square wave, a sawtooth wave, strain gauge data of an impact of a nonlinear beam, and audio data of a noisy microphone recording, are reported. By learning both the frequency and amplitude, this circuit could be used to enhance applications of AOs for robotic gait, clock oscillators, analog frequency analyzers, and energy harvesting.

Stability Analysis of Voltage Controlled Buck Converter Feed From a Periodic Input

Abstract: The ripples of dc input voltage belong to cascaded systems are usually close to the sinusoidal voltage, and its stability is quite different from that of dc constant voltage converters. Under the premise of no loss of generality, this article takes the output voltage of front-end converter in a cascaded system as sine wave, discusses the principle of closed-loop switching converters driven by sinusoidal input voltage, and calculates the average value of fixed-point state variables by using a discrete-time mathematical model. In addition, Filippov method is adopted to predict bifurcation by calculating the eigenvalues of Monodromy matrix belonging to the whole system, and the mechanism of nonlinear phenomena is also addressed. The results show that bifurcation points change obviously under different input conditions. Moreover, the influence of sinusoidal ripples amplitude and phase shift on bifurcation behavior is discussed, the compensation technique is used to prevent bifurcation and obtain the extended stability region of the circuit parameters. The experimental results prove the validity of the analysis.

A General and Accurate Iron Loss Calculation Method Considering Harmonics Based on Loss Surface Hysteresis Model and Finite-Element Method

Abstract: In order to predict the performance of designed electric machines, and also based on which the high efficiency of the drive systems can be obtained, the accurate calculation of the iron loss is necessary. Taking modeling accuracy versus modeling complexity into account, this article proposes a general and accurate iron loss calculation method considering harmonics based on the loss surface (LS) hysteresis model and finite-element method (FEM). Compared with the previous triangular wave excitation, this article uses the data under sinusoidal wave excitation to establish the LS model, which is more convenient for engineering application. A specimen is tested for different flux densities with harmonics, the extensive results verify the modeling method. Due to a powerful hysteresis model, the iron loss calculation can be realized by the direct integration of hysteresis loops. A separated iron loss calculation package is developed, and it is combined with the commercial finite-element software to compute the iron loss distribution. The method that combines the LS model and FEM is proved feasible by comparing the calculated iron loss with the measured one for the Epstein frame.

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

Abstract: The paper presents a method for the frequency characterization of voltage transformers (VTs) for medium voltage (MV) grids which involves only sine waves. It is called extended SINDICOMP, since it is an extended version of the previously developed technique SINDICOMP. It requires, in the first step, an evaluation and a compensation of the non-linearity introduced by the VT when it is supplied with a 50 Hz sinusoidal input at rated value. Then, the VT is characterized with a low voltage sinusoidal frequency sweep from the second harmonic frequency up to the first resonance frequency. Some rules to build the approximated frequency response, starting from these two sets of data, are given in the paper. The proposed approach is applied to three commercial MV VTs. Significant improvement of the VT performance is obtained, compared to the use of a frequency response obtained from the low voltage characterization.

A dual-mode excitation method of flexure hinge type piezoelectric stick-slip actuator for suppressing backward motion

Abstract: Backward motion directly limits the output performance of piezoelectric stick-slip actuators, and it has been suppressed or eliminated by various means. To suppress the backward motion, a dual-mode excitation method (DMEM) is proposed in this paper, which utilizes a piezoelectric stack and two piezoelectric plates as the main and auxiliary excitation sources of the actuator respectively. When the piezoelectric stack contracts rapidly under the traditional sawtooth wave, two piezoelectric plates excited by high-frequency sine wave make the driving foot generate ultrasonic vibration. Accordingly, the backward motion can be suppressed based on ultrasonic friction reduction to improve the output performance of actuator. To reflect the advantage of the proposed method, a flexure hinge type piezoelectric stick-slip actuator is manufactured, and the characteristic experiments are executed. According to the experimental results, the backward rates of actuator driven only by sawtooth wave are 42 % and 28 % in the clockwise and counterclockwise directions, the corresponding velocities are 252.74 mrad/s and 316.45 mrad/s, the corresponding loads are 8 g and 9 g, respectively. By comparison, the backward rates of actuator under the DMEM decrease by 10 % and 5 % along these two directions, the velocities improve by 17 % and 9 %, and the loads increase by 13 % and 11 %, respectively.

Design and Control of a Three-Phase T-Type Inverter using Reverse-Blocking IGBTs

Abstract: This paper proposes the design and implementation of a 15kW three-phase T-type inverter. Fuji Electric's new generation IGBT module (V series) using RB-IGBT technology is applied for the converter, due to its higher efficiency from conventional IGBTs to reduce switching losses on the semiconductors. Under full load conditions, the overall efficiency of the converter can reach over 98%. The control design and sine PWM modulation are implemented on a DSP kit named TMS320F3F28379D. In addition, the PWM is generated with the fundamental and third harmonics of a sin wave, allowing a modulation factor up to 1,154 compared to traditional PWM. The output voltage of 220V/50Hz with less than 2% of THD can be achieved at the minimum input DC voltage of 550V.

The Power Losses in Cable Lines Supplying Nonlinear Loads

Abstract: This paper presents the skin effect impact on the active power losses in the sheathless single-core cables/wires supplying nonlinear loads. There are significant conductor losses when the current has a distorted waveform (e.g., the current supplying diode rectifiers). The authors present a new method for active power loss calculation. The obtained results have been compared to the IEC-60287-1-1:2006 + A1:2014 standard method and the method based on the Bessel function. For all methods, the active power loss results were convergent for small-cable cross-section areas. The proposed method gives smaller power loss values for these cable sizes than the IEC and Bessel function methods. For cable cross-section areas greater than 185 mm2, the obtained results were better than those for the other methods. There were also analyses of extra power losses for distorted currents compared to an ideal 50 Hz sine wave for all methods. The new method is based on the current penetration depth factor calculated for every considered current harmonics, which allows us to calculate the precise equivalent resistance for any cable size. This research is part of our work on a cable thermal analysis method that has been developed.

Instrument Transformers for Power Quality Measurements: a Review of Literature and Standards

Abstract: Measurements of Power Quality (PQ) are gaining more importance due to increasing presence of switching power converters that deform the waveform of the distributed voltage further and further away from a sine wave. Especially at medium and high voltage levels, PQ measurements are carried out by means of Instrument Transformers (ITs). A recently started European metrology project, EMPIR 19NRM05 IT4PQ, aims at establishing the methods and procedures for assessing the accuracy of ITs used for PQ measurements. This paper, that is written in the framework of the IT4PQ project, presents a thorough review of the current state-of-the-art of literature and international standards about ITs and PQ. The main results from several papers and the main information from IT and PQ related international standards are summarized.

A revised manuscript submitted to sensors and actuators B: Chemical illumination modification from an LED to a laser to improve the spatial resolution of IGZO thin film light-addressable potentiometric sensors in pH detections

Abstract: Indium Gallium Zinc Oxide (IGZO) on Indium Tin Oxide (ITO) glass has been applied as the semiconductor substrate of a light-addressable potentiometric sensor (LAPS) with the advantages of immunity to room light inference and high photocurrent. For the first time, investigations into this IGZO LAPS including two-dimensional (2D) chemical imaging and reduction of the potential biorelative damage induced by the requirement of an ultraviolet (UV) light source are presented in this study. For the spatial resolution, a smaller aperture for the light spot provided by a light emitting diode (LED) makes the photocurrent decrease. To overcome this natural limitation, the type of AC modulation of light source is changed from a sine wave to a square wave with different duty cycles. The photocurrent and power consumption of a 365 nm LED with square wave and a duty cycle of 40 % are 42.2 % higher and 16.2 % lower than those of the conventional setup of a sine wave, respectively. The pH sensitivity, linearity, hysteresis and drift are comparable. The illumination wavelengths of 365, 405 and 435 nm are studied for photoresponse. 405 nm illumination with acceptable pH sensing performance can be suggested for IGZO LAPS for less bio damage concern. Additionally, a laser with a wavelength of 405 nm with spot size of 25 μm and scanning step of 2 μm is proven to have a clear pattern recognition down to 50 μm in 2D image. Further optimization of the spot size of the laser, thickness and composition of IGZO are suggested for better spatial resolution.

Decomposing Non-Stationary Signals With Time-Varying Wave-Shape Functions

Abstract: Modern time series are usually composed of multiple oscillatory components, with time-varying frequency and amplitude contaminated by noise. The signal processing mission is further challenged if each component has an oscillatory pattern, or the wave-shape function, far from a sinusoidal function, and the oscillatory pattern is even changing from time to time. In practice, if multiple components exist, it is desirable to robustly decompose the signal into each component for various purposes, and extract desired dynamics information. Such challenges have raised a significant amount of interest in the past decade, but a satisfactory solution is still lacking. We propose a novel nonlinear regression scheme to robustly decompose a signal into its constituting multiple oscillatory components with time-varying frequency, amplitude and wave-shape function. We coined the algorithm shape-adaptive mode decomposition (SAMD) . In addition to simulated signals, we apply SAMD to two physiological signals, impedance pneumography and electroencephalography. Comparison with existing solutions, including linear regression, recursive diffeomorphism-based regression and multiresolution mode decomposition, shows that our proposal can provide an accurate and meaningful decomposition with computational efficiency.

Partial Discharge Measurement of Power Module Packaging Insulation Under Square Wave with Short Transition Time Based on SHF-Down-Mixing Method

Abstract: Exploring the partial discharge (PD) characteristics of power modules under square wave high electric fields with short rise and fall time is of great significance for improving the reliability of its packaging insulation. In this paper, a PD detection method based on super high frequency (SHF, 3-30 GHz) technique and signal down-mixing principle is applied to detect the PD under square wave. The power module packaging insulation specimen consisting of metal baseplate, direct bonding copper (DBC), substrate and housing is fabricated. A repetitive square wave generator is built to supply high voltage square waves with short transition time. PD experiments are performed under square wave and sinusoidal wave. Experimental results show that the SHF-down-mixing PD detection system can effectively suppress the electromagnetic interference (EMI) from the square wave and extract PD signals successfully. As the radius of the electrode corner increases, the partial discharge inception voltage (PDIV) values under the sinusoidal wave also gradually increases. The PDIV under square wave does not show a monotonically increasing and is usually higher than that under sinusoidal wave probably because of the effect of space charge accumulation.

Switched Capacitor Based High Bandwidth Envelope Tracking Power Supply

Abstract: The envelope tracking (ET) power supply can output a variable voltage which tracks the envelope of the radio frequency input signal to the power amplifier (PA), and the system efficiency can be significantly improved. To achieve a high tracking bandwidth, the switching frequency of the ET power supply is usually too high. The pulse edge independent distribution (PEID) method has been proposed to reduce the switching frequency to 1/ n ( n ∊ N) of the tracking bandwidth, but a large number of isolated voltage sources are needed, leading to increased power stage and system complexity. In this letter, a switched capacitor based high bandwidth ET power supply is proposed, which employs optimized charging topologies and mechanisms to stabilize the voltages across the switched capacitors, and thus they can fully replace the isolated voltage sources. Since the proposed configuration is derived from the PEID method, all the features of PEID method are retained. A prototype with 6−26-V output voltage and 20-W peak output power is fabricated and tested with a 1-MHz sine wave and a 5-MHz bandwidth communication envelope. The experimental results validate the proposed configuration.

A MHz LLC Converter Based Single-Stage Soft-Switching Isolated Inverter with Hybrid Modulation Method

Abstract: The inverter that requires isolation typically consists of an isolated dc-dc and a pulse-width-modulated dc-ac stages. However, the component counts, control complexity, efficiency and power density tend to be suffered with such a two-stage configuration. In this paper, a single-stage soft-switching isolated inverter based on MHz LLC converter is introduced with a novel hybrid modulation method, which operates under full-bridge and half-bridge variable frequency conditions for high- and low-line outputs, respectively. A rectified sine wave can be generated at the output of LLC converter and isolated through a high-frequency transformer for additional voltage gains. A lossless line frequency unfolder circuit is added afterwards to convert the rectified sine wave to ac sine output. The optimization method for the resonant tank is also proposed to achieve even lower voltage gains at high frequency to improve the output ac waveform quality. Compared to the traditional two-stage method, this single-stage solution makes the circuit simpler, and the bulky dc bus capacitor can be saved. To verify the circuit design and the proposed hybrid modulation method, a GaN based 380 V dc – 600 V ac , 1.2 kW prototype is built and tested. Under the full load condition, the measured total harmonic distortion of output voltage is 2.67% with 98.30% efficiency for the overall inverter.

Performance Evaluation of Solar Air Heater Using Sine Wave Shape Obstacle

Abstract: Numerical analysis of thermo-hydraulic performance parameter (ƞ) of a solar air heater having sine wave shape obstacles is carried out and compared with a flat plate air heater. The second-order upwind scheme is used for discretization of the fluid domain and governing equations are solved by the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. Shear Stress Transport (SST) k–ω turbulence model is used for modeling turbulence. The numerical analysis encompasses Reynolds number (Re) ranging from 4000 to 16,000, and angle of attack (α) ranging from 0° to 45°, while the relative roughness transverse pitch (p/e) is kept 10. Numerical analysis is performed by using computational software ANSYS Fluent 15.0. The thermo-hydraulic performance parameter (ƞ) based on Nusselt number (Nu) and the friction factor attained maximum value at (p/e) of 10 and α of 30°.

Estimating Parameters of a Sine Wave by the Method of Variable Projection

Abstract: This paper presents a new derivation and implementation of the method of variable projection for the estimation of the parameters of a sine wave model. The new approach yields insights into the cost function associated with the model and how this behaves when there is less than one cycle of the signal in the measurement period. Additionally, the new method delivers the covariance matrix for the linear parameters; permitting computations of prediction and confidence intervals for the approximation. The method is thoroughly tested using Monte Carlo simulations and the results compared with those obtained by Chen.

Temporal optical besselon waves for high-repetition rate picosecond sources

Abstract: We analyse the temporal properties of the optical pulse wave that is obtained by applying a discrete set of spectral π/2 phase shifts to continuous-wave light that is phase-modulated by a temporal sinusoidal wave. We develop an analytical model to describe this new optical waveform that we name ‘besselon’. We also discuss the reduction of sidelobes in the pulse intensity profiles by means of an additional spectral π phase shift, and show that the resulting pulses can be efficiently time-interleaved. The various predicted properties of the besselon are confirmed by experiments demonstrating the generation of low duty cycle, high-quality pulses at repetition rates up to 28 GHz.

FPGA-based digital chaotic anti-interference lidar system.

Abstract: We use the chaotic signal generated by a field-programmable gate array (FPGA) to establish a digital chaotic pulse lidar system, which can achieve mid-range detection and high ranging accuracy without a complex optical structure. We employ the FPGA to generate random sequences with different modulation rates based on different chaotic iterative equations and initial values. By selecting the initial value and improved logistic equations, we successfully achieve centimeter-level ranging accuracy. Experiments have proved that the digital chaotic lidar system can effectively resist the interference of chaotic signals, square wave signals, and sine wave signals with modulation frequencies of 10 MHz, 100 MHz, 200 MHz, and 1 GHz, showing its strong anti-interference capability.