Sinusoidal Phase Shift Research Articles

Sinusoidal Phase Shift Modulation for V2H Operational Mode in Current-Fed Bidirectional Onboard Charger

Sinusoidal Phase Shift Modulation for V2H Operational Mode in Current-Fed Bidirectional Onboard Charger

Optimization of the effect of sinusoidal phase shift heating on mixed convective in an enclosure: LBM approach

This paper investigates the influence of mixed convective heat transfer in a two-dimensional enclosure with sinusoidal heat applied on the vertical walls by the Lattice Boltzmann Approach. Governing equations are resolved by the Single-Relaxation-Time Bhatnagar-Gross-Krook model. A two-dimensional, nine-directional lattice arrangement is chosen to attain better numerical stability with good accuracy. The results are presented for four different fluids having Prandtl numbers equal to 0.015, 0.7, 1.38, and 7.0 respectively for mercury, gaseous ammonia, noble gases, and water. This analysis is performed for selected Reynolds numbers (100 ≤ Re ≤ 2000) and Richardson numbers (0.0 ≤ Ri ≤ 10.0). The above parameters are optimized using the Design of the Experiment to achieve maximum heat transfer rate. Taguchi method is used to conduct the required numbers of numerical studies and the dominant parameters are quantitatively found using Analysis of Variance (ANOVA). The present numerical results are compared with the existing literature and found good agreements. Results show that the right-side wall has always a higher heat transfer rate than the left-side wall. The factor levels combination for maximum heat transfer rate is found as Pr = 7.0, Re = 2000, and Ri = 10.

Flattop Modulation Technique for a Low-Device Count Single-Stage AC-DC DAB Converter to Improve Its Overall Efficiency

This article proposes a flattop modulation technique for a single-stage, single-phase bidirectional ac-dc dual-active-bridge (DAB) converter for achieving a flattopped DAB inductor current. The flattopped DAB inductor current has a low root mean square (rms) value, and it improves the soft-switching performance of the converter. The novelty of the proposed technique is that it guarantees flattopped DAB inductor current throughout the ac line cycle and has direct control over the ac current. In this technique, sinusoidal pulse width modulation (PWM) is performed at the ac side bridge for direct ac current control. Sinusoidal phase shift modulation is performed at the dc side to generate a bridge output voltage with a pulsewidth identical to the ac side bridge. The high-frequency (HF) transformer turns ratio is appropriately selected to match the voltages at the DAB inductor’s ends. Thereby, flattop DAB inductor current is achieved throughout the line cycle. The proposed modulation technique ensures a regulated dc bus at the ac side and provides a ripple-free ac current by interleaving. The operation of the converter under the flattop modulation technique is analyzed in detail, and parameter design guideline is provided. Experimental results from a 2-kW converter prototype support the theoretical claims.

Design and performance analysis of asymmetric multilevel inverter with reduced switches based on SPWM

<span lang="EN-US">Multilevel inverters have the benefit of producing high output voltage values with little distortion. This paper deals with decreasing total harmonic distortion (THD) and providing an output voltage with various step levels switching devices. In this study, a 27-level inverter with three asymmetric H-Bridge was designed and simulated based on level shift sinusoidal pulse-width modulation and phase shift sinusoidal pulse-width modulation methods. MATLAB/Simulink has been used to create this model and test it at different types of loads. The results showed that a multilevel inverter with (PS-PWM) produces less (THD) than a multilevel with (LS-PWM), when the resistive load was used, the produced voltage and current THD in (PS-PWM) and (LS-PWM) are 3.02% and 4.30% respectively, that has resulted from the linearity between voltage and current in the resistive load. While in the case of applying an inductive load, the THD in the voltage is constant in both (PS-PWM) and (LS-PWM) methods and has the same values as the THD in a resistive load. However, the THD in the current with inductive load decreased to 2.79% in (PS-PWM) and 4.04% in (LS-PWM). Finally, these results show that the performance of the proposed power circuit with PS-PWM is better than (LS-PWM).</span>

Encoding technology of an asymmetric combined structured light for 3D measurement.

Sinusoidal phase-shifting symmetrically combined with cyclic code is one of the most important encoding methods in the field of 3D measurement. Due to the modulation of the object surface and the influence of the noise of the image acquisition system, the periods of the cyclic code and the sinusoidal phase-shifting in the intensity image do not coincide completely, and they lead to large absolute phase decoding errors near the cycle boundaries, which are called cycle dislocation errors. In order to eliminate these errors in principle, the concept and method of region encoding for four-step sinusoidal phase-shifting are proposed, and the sinusoidal phase-shifting is combined with cyclic code asymmetrically. Under the premise that the cyclic code and the region code change at different times, the cycle dislocation error is reduced from one cycle of cyclic code to one pixel by the dual constraint of cyclic code and region code. The simulation measurement results of 3ds max and the physical measurement results show that the asymmetric combination encoding method effectively eliminates the cycle dislocation errors; the maximum measurement error is reduced by an order of magnitude, and the root mean square measurement error is reduced by 70%.

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

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.

Integrating-bucket phase stabilization method for fiber-optic fringe projector

Ac phase tracking technique (PTAC) is an established and effective method for phase stabilization of fiber-optic fringe projectors (FoFP), but it may reduce the fringe visibility owing to the introduction of an extra sinusoidal phase modulation. In this paper we propose an integrating-bucket method to stabilize the phase of FoFPs which is applicable to both linear phase shifting (LPS) profilometry and sinusoidal phase shifting (SiPS) profilometry. The method requires no extra modulation of the interference phase; instead, it divides the interference signal period into N (N > 2) episodes with equal time intervals and directly integrates these episodes to obtain N discrete data. By manipulating these data the interference phase can be calculated and accordingly phase disturbance can be eliminated by the feedback loop. The proposed method is as effective as the PTAC technique but at the same time more computationally efficient because the operations involved are merely add, subtraction and arctangent solution. We built a digital phase controller with the proposed method, and managed to restrict the maximum phase drift of an FoFP to within 15 mrad in 5 min for both LPS and SiPS, which is similar to the result obtained with the PTAC technique. What’s more, we measured the mean value variation of the recovered phase map of a stabilized FoFP profilometer, and results are 30 mrad for LPS and 50 mrad for SiPS in 5 min.

High Accuracy Multi-Channel SPWM Generator Based on Digital Natural Sampling

Principle of triangle carrier amplitude modulation is equivalent with sinusoidal modulator amplitude modulation, and principle of sinusoidal modulator phase-shifting is equivalent with the triangle carrier phase-shifting are proposed. A digital natural sampling based on multi-channel SPWM generator is developed using time-division multiplexed access (TDMA). Flip time computation by CPU is no needed in the generator which has an accuracy flip time. Design principle and implementation based on FPGA are introduced, and testing results are presented.

Design of error-compensating algorithms for sinusoidal phase shifting interferometry

An improved approach to interferometry using sinusoidal phase shifting balances several harmonic components in the interference signal against each other. The resulting computationally efficient phase-estimation algorithms have low sensitivity to errors such as spurious intensity noise, vibration, and errors in the phase shift pattern. Specific example algorithms employing 8 and 12 camera frames illustrate design principles that are extendable to algorithms of any length for applications that would benefit from a simplified, sinusoidal phase shift.

Photorefractive devices

In this paper we review four photorefractive devices which have been investigated and further developed in our laboratories. We discuss the fundamental behavior of a photorefractive Bi12SiO20 autocorrelator optimized for particle image velocimetry. The all optical correlator determines the velocities of particles in a cross section of a flow. We show that the autocorrelator is perfect for investigating both laminar and turbulent flows. Photorefractive materials can also be used for vibration analysis of diffusely scattering structures. We discuss recent work from a four-wave mixing interferometric setup with Bi12SiO20 and show that introducing a proper sinusoidal phase shift in one of the pump beams leads to a complete mapping of the vibrational phase and amplitude everywhere on the vibrating structure. Photorefractive materials are also promising candidates for optical storage devices. We discuss holographic storage in LiNbO3 and describe a detailed procedure to obtain a high signal to noise ratio in this device. Finally, we discuss the photorefractive interference filter which consists of alternating quarter-wave layers of high and low index. It has a unique high wavelength selectivity, and the reflectivity and center wavelength can be controlled dynamically by two external laser beams.

Quantitative measurement of the vibrational amplitude and phase in photorefractive time-average interferometry: A comparison with electronic speckle pattern interferometry

Time-average interferometry is dealt with using four-wave mixing in photorefractive Bi12SiO20. By introducing a proper sinusoidal phase shift in the forward pump beam it is possible to measure the amplitude and phase everywhere on a vibrating object. Quantitative measurements of the phase and amplitude of the vibrating structure are demonstrated in photorefractive time average interferometry. The photorefractive interferometer is compared with the performance of a commercial electronic speckle pattern interferometer (ESPI). It is shown that the dynamic photorefractive holographic interferometer improves the image quality considerably and is able to extend the measurable range for the acoustic vibration amplitude and frequency compared to what is obtainable with the ESPI equipment.

Enhanced four-wave mixing in photorefractive BSO produced by temporal phase shifts

This paper dealt with the experimental observation of enhanced four-wave mixing in BSO. The method used involves sinusoidal phase shift in one of the pump beams. Due to this phase shift a sum of frequencies is present in the temporal modulated intensity on the crystal. The method used provides both phase and amplitude information on the photorefractive effect. Expressions for both these parameters are obtained. A mode operation of the phase conjugator has been demonstrated.