Step Sine Wave Research Articles

Quasi-anechoic frequency response measurement of underwater acoustic devices using exponential sine sweeps

As part of the development of the MITRE BlueTech Lab, an existing 106 × 40 × 15 ft. underground tank is being repurposed as an underwater acoustic test facility. Here, we report on the development of a procedure to extract anechoic frequency responses from measurements made in the otherwise reverberant environment using exponential sine sweeps. A demonstration of the procedure applied to a small-aperture baffled receiver array is shown, and results are compared to time-gated stepped sine wave measurements. Simple geometric rules to maximize measurement bandwidth while ensuring far-field conditions for both transmitter and receiver array are presented.

Simulation of a Low Cost Single Phase to Three Phase Converter using Arduino

This paper proposes a single phase to three phase conversion system composed of a rectifier, capacitive filter, Arduino controller, resistive switching network, buffer circuit and amplifier circuit. The proposed topology permits to operate at different frequencies by changing the coding of Arduino pulse generator. Although the effectiveness of previous work is acknowledged, none have assessed the multilevel wave generation using arduino and resistive switching network. It reduces the cost by using resistive switching technique and better accuracy as the input pulse is divided into 20 steps and finally a stepped sine wave is obtained. This converter can be easily used for motors up-to 5HP. Analysis and simulated results are presented to validate these features.

Three-dimensional laser Doppler vibrometry of the dry human skull.

The results of an experimental study of the vibratory response of the dry human skull at acoustic frequencies (250 Hz–16 kHz) are presented. In three dry skulls, the motor from a clinical bone vibrator, the BAHA Divino, was used to excite vibrations, and the amplitude and phase of the response were measured with a Polytech PSV-300 scanning laser Doppler vibrometer. Data were acquired at 2200 points covering the entire skull surface at ∼5 mm resolution. The experiment followed a stepped-sine paradigm with excitation frequencies spaced linearly at 200 Hz. The experiments show that the dry skull undergoes quasi-rigid motion at low frequencies, which breaks up into modal vibration patterns above 1000 Hz. At frequencies above 8000 Hz, clear standing wave patterns can be seen with wavefronts radiating out from the excitation location. The data are consistent with the response being primarily plate-bending motion. Progress of reproducing the data with a finite element model will also be reported. Geometry for the model was acquired using a high-resolution CT scan imported into HyperMesh® and the simulation was performed in LS-DYNA® hydrocode. [Work supported by the Atlantic Canada Opportunity Agency’s (ACOA) Atlantic Innovation Fund and the Natural Sciences and Engineering Research Council (NSERC).]

Stepped sine wave DC/AC inverter. I. Theoretical analysis

Abstract The DC/AC inverter is a basic building block of both stand alone (supplying AC load) and grid connected photovoltaic systems. A detailed analysis of the stepped sinusoidal waveform and associated harmonic contents is presented. The considered waveform consists of multiple steps of equal amplitudes. The number of steps as well as the duration of each step are optimized. The optimization criterion is the maximum DC/AC inverter efficiency. The analysis is divided into two parts. Firstly the stepped sine wave efficiency is determined in terms of the number of steps and the duration of each step. It is proved that the waveform efficiency improves as the number of steps increases. Secondly, the inverter circuit efficiency is determined in terms of the number of steps. It is shown that the circuit efficiency is independent of the number of steps of the stepped sine wave. Moreover, the inverter cost is related to the number of steps of the stepped sine wave. The inverter circuit complexity and consequently the cost increases as the number of steps increases. The inverter reliability — on the other hand — decreases as the inverter circuit becomes more complex. The optimization criterion depends on the economics of the system where the DC/AC inverter is used.

Stepped sine wave DC/AC inverter II. Circuit design

Abstract This work presents a detailed design and the experimental results of a stepped sine wave DC/AC inverter. The design criterion is to build an inverter of low cost, easy to repair, reliable and of high efficiency. The electronic components used in the inverter are of low cost and commercially available in developing countries. No special components such as toroidal transformers or high cost switching devices are employed. The design with available components enables easy maintenance and short repair periods for the inverter. As a result the inverter reliability increases. Protection circuits against overload, overtemperature of switching devices and low battery voltage are included in the design. A 500 W prototype inverter is built and tested in the laboratory. Good agreement between theory and measurements is observed. The prototype inverter is tested with both resistive and inductive loads and good reliability is observed. An inverter efficiency exceeding 90% is measured.

Computer-aided analysis of stepped sinewave inverters

Abstract A stepped sinewave full-bridge inverter was analysed theoretically to determine its optimum working conditions, its minimum number of components, and characteristic of its constituent components and control circuit of its power switches. A computer program, written in FORTRAN-77, was developed to analyse this inverter circuit. The program prompts for input data such as the characteristics of the power and control circuit elements, the output fundamental frequency, and the number of available batteries and their voltage. The output of the program is designed to give the optimum stair widths, the loss, the harmonic and the total efficiency, the harmonic distortion, the sensitivity of the efficiency and fundamental voltage to the variation in stair width, and the energy withdrawal from each battery for the power switches controlling the circuit. Interesting design data for this circuit were also obtained.

Load independent efficient, transformerless inverter for photovoltaic applications

The overall efficiency of photovoltaic power systems (PVPS) depends on the efficiency of the PV panels, the storage batteries, and the efficiency of the inverter circuitry. The last is greatly influenced by the connected load, as the efficiencies are severly reduced when operating at low loads. This is especially effective when the PVPS is most likely to operate with a fraction of the full load. The suggested inverter has excellent efficiency characteristics over a wide power range, and because it contains only electronic components further cost reduction can be expected. Experimentally this inverter is designed for a 120 W output using thyristor switching devices; the efficiency obtained is 88% at full load and 85.2% at 10% of full load, with a maximum output voltage of 60 V stepped sinewave with frequency of 50 Hz. However, higher power outputs could also be achieved with this type of inverter.

Determination of the Number of Cells in a Stepped Sine Wave Inverter for Equal Charge Transfer

The synthesis of an inverter sine wave output voltage by a staircase wave shape of low level voltage sources (cells) is accomplished by combining the cells in series at specific time intervals. Different cells of the inverter are then connected to the load for different time durations which results in unequal discharging of the cells. In order for the cells to transfer equal charge during the system operation, each voltage step should consist of a different number of cells in a parallel combination (module), the number of which depends on the time along the wave shape. The number of cells in each module is determined from the circuit current analysis and the appropriate switching time intervals, and is performed for a resistive and an inductive load. This number depends on the number of inverter voltage steps, the cell internal resistance, and the type of the load. The proper number of cells in the modules ensures identical state of charge of the cells, and equal cell recharging, and simplifies cell inspection, maintenance, and replacement.

Stepped Sinewave Inverter

A stepped sinewave dc/ac inverter was analyzed for an inductive load with respect to load current and voltage, harmonics, power factor, and efficiency. This special inverter of high efficiency and low harmonic content is constructed by synthesizing the sinusoidal output by discrete voltage sources, such as storage batteries, solar cell, etc., with electronic switching of the sources at specific time intervals. The switching times are determined for the condition of minimum distortion of the synthesized wave. A 50 W inverter was built and tested to demonstrate this approach.

Transient signal propagation through an inhomogeneous plasma

The propagation of a transient electromagnetic field through a cold, isotropic, lossless, inhomogeneous plasma is considered. The electron density of the plasma decreases exponentially in the direction of propagation. For incident transient signals whose Laplace transforms are regular at infinity and whose only singularities are poles, the transient electric field propagated through the plasma can be expressed as a sum of exponential waves at discrete complex frequencies. The characteristic frequencies of the inhomogeneous plasma are related to the zeros of the modified Bessel function of the first kind of fixed argument and variable order. When the Laplace transform of the incident signal is not well-behaved at infinity, approximate methods may be used to evaluate the transient electric field. The propagation of a step sine wave and of a quasi-monochromatic Gaussian pulse are considered. It is found that for plasmas characteristic of reentry boundary layers, the effect of the plasma layer on dispersion is very small. The principal effect of the layer is to attenuate a signal propagated through it.