Low-frequency Sinusoidal Signal Research Articles

Precise pointing angle deviation measurement forbeaconless laser communication.

How to measure the pointing angle precisely without the beacon light is crucial for beaconless laser communication. The conventional intensity method directly measures the intensity of a part of the communication signal beam, which has low sensitivity. We propose the characteristic signal method by superimposing a low-frequency sinusoidal signal on the communication signal to promote the measuring sensitivity. Simultaneously, a fast cyclic cross-correlation algorithm is used to reduce operational complexity. Compared with the experimental results of the direct intensity method, the proposed method can improve the measuring sensitivity about 9.17dB and increase the power budget for communication about 1.96dB.

Magnetic and electric antennas calibration for partial discharge charge estimation in gas-insulated substations

There are no accepted procedures that quantify the apparent charge of partial discharge (PD) in gas-insulated substations (GIS). This paper proposes a calibration method for PD charge estimation using unconventional electromagnetic sensors: a magnetic loop antenna (inductive coupler) and an electric antenna (capacitive coupler.) The calibration procedure is intended for the voltage double integral method, which is reviewed for magnetic antennas and extended for electric antennas. By injecting low-frequency sinusoidal signals, the calibration constants are determined for two different test setups: the first one being a testbench where the characteristic impedance is matched and the second one a full-scale 420 kV GIS. The calibration method is validated in three ways: with a calibrated pulse in the testbench, a calibrated pulse in a full-scale GIS, and PD defects in the full-scale GIS. The calibration procedure revealed a frequency limit range dependent on the GIS length and the sensor’s signal-to-noise ratio. The three validation methods showed low charge estimation errors for the magnetic and electric antennas, demonstrating that the PD calibration method applies to any electric/magnetic detector with a low-frequency derivative response. This research paves the way for better GIS insulation monitoring and PD sensor harmonization.© 2017 Elsevier Inc. All rights reserved.

Design of a Low-Frequency Harmonic Rotary Piezoelectric Actuator

Piezoelectric actuators usually operate under a high frequency driving signal. Here we report a harmonic rotating piezoelectric actuator by coupling a harmonic wave generator and a friction rotor, in which the actuator can be actuated by a low-frequency sinusoidal signal with positive bias. The harmonic wave is generated by a two-stage magnifying mechanism consisting of a displacement amplifier and a harmonic rod. Applying piezoelectricity theory, the actuator’s output characteristic equations are deduced. What is more, the output characteristics of piezoelectric actuators are tested with the established experimental system. Results show that the generated harmonic displacements can drive the actuator to work normally at a driving voltage of larger than 90 V and the maximum total harmonic displacement of the piezoelectric actuator comes up to 427.6 μm under the driving voltage of 150 V. Meanwhile, the error between the measured and calculated values of the harmonic displacement is less than 7%. Furthermore, the rotational speed of the piezoelectric actuator reaches 5.45 rpm/min at 150 V voltage and 5 Hz driving frequency.

An Adaptive Identification of Rotor Time Constant for Speed-Sensorless Induction Motor Drives: A Case Study for Six-Phase Induction Machine

Accurate rotor time constant ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> ) value is necessary to ensure an acceptable performance of the indirect field-oriented control (IFOC) strategy, where a detuned <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> affects rotor flux orientation and, in turn, results in poor dynamic and steady-state response of torque. The problems associated with detuned <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> will be exacerbated in sensorless drives when a model-based speed estimation algorithm is employed. This article investigates the problem of simultaneous identification of the rotor time constant and rotor speed for sensorless IFOC of six-phase induction motor (6PIM) drives. First, an adaptive observer is proposed for online detection of the low-frequency sinusoidal signal, which is intentionally injected into the rotor flux command. Then, a novel model reference adaptive system (MRAS)-based <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> estimator is proposed using the detected signal. The Lyapunov stability theorem is used to ensure the asymptotic stability of the proposed identification system. The proposed method is based on the induction machine (IM) model in primary subspace, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> subspace. Hence, it is usable for other multiphase IM (three phases and higher). Nevertheless, the 6PIM is adopted here as a case study. The simulation and experimental results clarify the effectiveness of the proposed parallel estimation system.

Implementation of 5-Level H-Bridge Inverter with Multicarrier based Modulation Techniques

Paper Setup must be in A4 size with Margin: Top In the present paper multi carrier sinusoidal modulation technique which is an efficient method of producing control signals is used for a symmetrical inverter with several levels in cascade H Bridge is discussed. The Cascaded H-Bridge performance output levels depend on the DC voltage sources used at the input side. With the help of two DC voltage sources, five level output can be obtained whereas three sources gives levels of seven in output voltage. In this paper, multi-carrier SPWM switching is obtained for switching of multilevel inverter based switches. Two signals are used in this switching method, among which one of the signals is reference which is a low frequency sinusoidal signal and the one is a carrier signal. In case of sinusoidal PWM method of modulation technique, the reference signal is a sinusoidal one and triangular signal can be used as a carrier signal. These types of inverters have the ability to generate inverted output voltage with an efficient harmonic spectrum and reliable output results. This document provides switching signal for H-bridge inverter structure which can improve harmonic performance. The 5-level multilevel inverter is simulated for traditional carrier-based pulse-width modulation (PWM) phase change carrier techniques. The total harmonic performance of the output voltages is analyzed for the two PWM control methods. The performance of the symmetrical PWM CHB is simulated using MATLAB-SIMULINK model. Model results show that THD can be minimized to a limit with level shifted modulation method of the sinusoidal pulse width. The results from the simulations show that the quality of the waveform of the output voltage improves with less loss and with a lower THD.

Control of crossflow-vortex-induced transition by unsteady control vortices

The fundamental mechanisms of a hitherto unstudied approach to control the crossflow-induced transition in a three-dimensional boundary layer employing unsteady control vortices are investigated by means of direct numerical simulations. Using a spanwise row of blowing/suction or volume-force actuators, subcritical travelling crossflow vortex modes are excited to impose a stabilizing (upstream) flow deformation (UFD). Volume forcing mimics the effects of alternating current plasma actuators driven by a low-frequency sinusoidal signal. In this case the axes of the actuators are aligned with the wave crests of the desired travelling mode to maximize receptivity and abate the influence of other unwanted, misaligned modes. The resulting travelling crossflow vortices generate a beneficial mean-flow distortion reducing the amplification rate of naturally occurring steady or unsteady crossflow modes without invoking significant secondary instabilities. It is found that the stabilizing effect achieved by travelling control modes is somewhat weaker than that achieved by the steady modes in the classical UFD method. However, the energy requirements for unsteady-UFD plasma actuators would be significantly lower than for steady UFD because the approach makes full use of the inherent unsteadiness of the plasma-induced volume force with alternating-current-driven actuators. Also, the input control amplitude can be lower since unsteady crossflow vortex modes grow stronger in the flow.

Design and performance analysis of a many-to-one configuration precise cable drive mechanism with high precision and large torque

Precise cable drive is a flexible frictional transmission method that transmits power from drive capstans to driven pulleys by a properly preloaded transmission medium. Since most of precise cable drive mechanism with high pointing precision proposed in previous studies suffer from low transmission stiffness and small output torque, this paper presents a novel many-to-one configuration precise cable drive mechanism (MCCDM) with high precision and large torque. The design methods of many-to-one configuration are studied including the system optimal design and cable wrapping design. The transmission characteristics of the developed configuration are analyzed, considering transmission capacity, transmission backlash, and transmission stiffness. The corresponding parameter sensitivities are also investigated. Moreover, a prototype of the MCCDM has been built, with which a series of experiments are carried out. It is noted that the developed mechanism has a motion range of ±2 rad. The steady-state error to a step reference of 1 rad amplitude is only 1.39 µrad and the position resolution is better than 0.5 µrad. This mechanism could achieve maximum output torque of 35 Nċm with compact size and light weight. It has reached a considerable toque-to-weight ratio of 8.997 N·m/kg. The experimental results show that the self-excited oscillation and backlash are dominant nonlinear effects in the MCCDM system. It shows that the self-excited oscillation is a function of the rotational displacement in such a system, with the highest peak at 0.1669 cycle/mrad and the amplitude of 34.63 µrad. The backlash could be measured about 60 µrad under exciting of a small amplitude and low frequency sinusoidal signal. The proposed technologies could have strong technological implications in some special applications such as antenna servo system.

Simulation Method for Complex Multivalued Curves in Injection-Locked Oscillators

A new methodology is presented for the efficient harmonic-balance simulation of injection-locked oscillators with complex multivalued and disconnected curves. It is illustrated through its application to high-order subharmonically injection-locked oscillators. A graphical technique is applied to analyze the oscillator-phase sensitivity with respect to the input signal, required for the injection-locked operation. The intricate synchronized-solution curves are obtained with the new method, which enables a global exploration of all the coexistent periodic solutions. These solutions can belong to different curve sections, in a multivalued response, or to disconnected synchronization curves. The method is based on the calculation of a series of phase-dependent outer-tier admittance functions, which provide the oscillator response to the injection signal. Coexistent solutions are simultaneously obtained through a contour-plot intersection, without the need for continuation techniques. The method is illustrated through application to an oscillator synchronized to low-frequency sinusoidal signal by means of a nonlinear-transmission line. The analysis and design techniques have been successfully validated through comparison with independent simulations and measurements.

An Improved Magnetic Tracking Method Using Rotating Uniaxial Coil With Sparse Points and Closed Form Analytic Solution

A set of triaxial magnetic transmitting coils fed with low frequency sinusoidal signals can be tracked with a rotating uniaxial sensing coil. This is because the specific output signal of the sensing coil will reach a maximum value when the direction of its induced magnetic field points to the transmitting coils. Usually, a rotating method is used to find the maximum output direction based on the output signals from the sensing coil. This method needs a horizontal rotation phase and a vertical rotation phase to search for the maximum output and its accuracy depends on the rotation step size. In order to simplify the rotation process while maintaining the accuracy without reducing the rotation step size, an improved magnetic tracking method is proposed in this paper. It is found that when the sensing coil rotates in the horizontal plane, the specific output signals compose a sinusoidal curve. By extracting the amplitude, phase, and dc component of this sinusoidal signal, the distance and direction information between the sensing coil and transmitting coils can be estimated and no vertical rotating phase is needed. Another advantage of this method is that the tracking accuracy does not depend on the rotation step size once the sampling rate fulfills the Nyquist-Shannon sampling theorem. Therefore, we can use sparse points to reconstruct the sinusoidal signal. Experimental results will show the effectiveness of this tracking method.

Frequency estimation of distorted non-stationary signals using complex H∞ filter

Mechanical vibration signals are always composed of harmonics of different order. A novel estimator is proposed for estimating the frequency of sinusoidal signals from measurements corrupted by White Gaussian noise with zero mean. Also low frequency sinusoidal signal is considered along with third and fifth order harmonics in presence of noise for estimating amplitudes and phases of different harmonics. The proposed estimator known as complex H∞ filter is applied to a noisy sinusoidal signal model. State space modeling with two and three state variables is used for estimation of frequency in presence of white noise. Various comparisons in terms of simulation results for time varying frequency reveal that the proposed adaptive filter has significant improvement in noise rejection and estimation accuracy. Comparison in performance between two and three states modeling is presented in terms of mean square error (MSE) under different SNR conditions .The computer simulations clearly indicate that two states modeling based on Hilbert transform performs better than three states modeling under high noisy condition. Frequency estimation performance of the proposed filter is also being compared with extended complex Kalman filter (ECKF) under same noisy conditions through simulations.

Oscillator-Based Reconfigurable Sinusoidal Signal Generator for ADC BIST

In order to perform an on-chip test for characterizing both static and transmission parameters of embedded analog-to-digital converters (ADCs), this paper presents an oscillator-based reconfigurable sinusoidal signal generator which can produce both high and low frequency sinusoidal signals by switching the oscillator into different modes. Analog and digital signals can additionally be produced concurrently in both modes to provide not only test stimuli, but also reference responses for the ADC built-in self-test. The generated oscillation signal amplitude and frequency can be easily and precisely controlled by simply setting the oscillator clock frequency and initial condition coefficients. Except for a 1-bit digital-to-analog converter and smoothing filter, this proposed generator is constructed entirely by digital circuits, and hence easily integrates this silicon function and verifies itself before testing the ADCs.

Dynamic range and intensity discrimination with high-rate pulse-train carriers: predictions from a stochastic model and comparison with performance for noise-modulated pulse-train stimuli

This work investigates the properties of the neural response to a low frequency sinusoidal signal with a high-rate pulse-train carrier using a stochastic auditory nerve model. The agreement between the theoretical predictions, model simulations, and psychophysical data is demonstrated. Theoretical prediction of threshold (THL) and the most uncomfortable level (UCl), thus dynamic range, is considered as a function of various stimulus parameters, including carrier rate. Performance of dynamic range and intensity discrimination are compared for sinusoidal amplitude-modulated stimuli with high-rate pulse-train carriers and noise-modulated pulse-train stimuli.

Possible involvement of the ampullary electroreceptor system in detection of frequency-modulated electrocommunication signals in Eigenmannia.

Behavioral and electrophysiological experiments were conducted to examine whether frequency-modulated electrocommunication signals are detected by the ampullary electroreceptor system in Eigenmannia. First, frequency-modulated electric organ discharges were found to contain a low-frequency component that could be detected by the ampullary system. Second, fish were successfully trained to distinguish a frequency-modulated signal, which contained a low-frequency component as in natural signals, from an artificial signal in which the low-frequency component was eliminated but still modulated in frequency. Subsequently, the trained fish responded without reinforcement to a low-frequency sinusoidal signal which mimicked the low-frequency component in the frequency-modulated signal, suggesting that the fish used the ampullary system to detect frequency modulation. Finally, physiological recording from ampullary afferent fibers demonstrated that they respond to frequency-modulated signals as predicted from the signal's low-frequency component. Electrophysiological study also showed that detection of frequency modulation by the ampullary system is immune to the presence of other constant electric organ discharges.

Estimating the parameters of a low frequency sinusoid with noise and harmonic distortion†

A digital method is presented for measuring the amplitude and frequency of low frequency sinusoidal signals. Theoretical and simulation results show that the proposed method is robust when the sinusoid is contaminated with noise. Moreover, the method can be adapted to eliminate the effect of harmonic distortion.