Sinusoidal Frequency Research Articles

Sinusoidal Frequency Estimator by Using Interpolation of Four DTFT Spectral Lines

This paper proposes a sinusoid frequency estimator by interpolating four Discrete Time Fourier Transform (DTFT) samples. Firstly, Discrete Fourier Transform (DFT) is performed on the received sinusoid. Then we find the positional information of the maximal DFT bin and obtain the coarse estimation results. Next, the proposed method uses four symmetrical DTFT samples on both sides of the maximal DFT bin to interpolate the signal frequency and obtain accurate estimation results. Simulation experiment results illustrate that the proposed method’s accuracy is higher than that of the competitive methods. When the signal-to-noise ratio (SNR) increases from 0dB to 90dB, the presented estimator performs better than the competitive methods.

A High Frequency Vibration Compensation Approach for Ultra-High Resolution SAR Imaging Based on Sinusoidal Frequency Modulation Fourier-Bessel Transform

A High Frequency Vibration Compensation Approach for Ultra-High Resolution SAR Imaging Based on Sinusoidal Frequency Modulation Fourier-Bessel Transform

Effect of acupuncture in combination with sinusoidal medium frequency electrotherapy on upper limb motor function of stroke patients

Effect of acupuncture in combination with sinusoidal medium frequency electrotherapy on upper limb motor function of stroke patients

Drivers’ Attention to Preview and Its Momentary Persistence

Participants used a position control system to track the center of a simulated winding roadway with preview that ranged from 0.3 to 1.0 s. Participants’ spatial distributions of attention were measured by perturbing the roadway with different frequency sinusoids at different roadway positions and then measuring the degree to which those frequencies were present in their tracking movements. Consistent with Miller's optimal control theory analysis of tracking with preview, participants exhibited a continuous range of attention, and it lengthened with the amount of displayed preview. When the displayed preview disappeared for 5 s, the time to reach a steady-state level of tracking error based only on feedback control was measured. More displayed preview was strongly correlated with longer times to regress to feedback control. One interpretation of this finding is that when preview is withdrawn, visual sensory memory of the previewed roadway can be used for a fraction of a second to prolong the period of feedforward control. Attention can be shifted to relevant positions of the sensory memory image to anticipate the roadway curvature. However, the quality and usefulness of sensory memory gradually diminishes until the participant can only perform feedback control. When preview was restored, the time to reach steady-state feedforward control was correlated with the range of attention. These findings characterize some of the dynamic aspects of attention when drivers are briefly interrupted from viewing the upcoming roadway. This measurement technique may be useful for characterizing spatially distributed attention in other active control contexts.

Fast interpolated DTFT estimators of frequency and damping factor of real-valued damped sinusoids

This paper deals with the estimation of real-valued damped sinusoid frequency and damping factor. To that aim an Interpolated Discrete Time Fourier Transform (IpDTFT) algorithm is proposed which extends to real-valued signal an algorithm proposed in the literature for complex-valued damped sinusoids. The proposed algorithm provides fast estimates of the unknown parameters of either undistorted or distorted real-valued noisy damped sinusoids with accuracy generally better than the one ensured by state-of-the-art estimators, especially when few sinusoid cycles are analysed. Accuracy improvement is obtained by both weighting the acquired signal using a Maximum Sidelobe Decay (MSD) window and compensating the contribution of the spectral image component on the estimated parameters. Analytical expressions for the estimator variances due to wideband noise are also derived.

SDPLL-Based Frequency Estimation of a Sinusoid in Colored Noise

The problem of frequency estimation of a single sinusoid observed in colored noise is addressed. Our estimator is based on the operation of the sinusoidal digital phase-locked loop (SDPLL) which carries the frequency information in its phase error after the noisy sinusoid has been acquired by the SDPLL. We show by computer simulations that this frequency estimator beats the Cramer-Rao bound (CRB) on the frequency error variance for moderate and high SNRs when the colored noise has a general low-pass filtered (LPF) characteristic, thereby outperforming, in terms of frequency error variance, several existing techniques some of which are, in addition, computationally demanding. Moreover, the present approach generalizes on existing work that addresses different methods of sinusoid frequency estimation involvingspecific colored noise models such as the moving average (MA) noise model. An insightful theoretical analysis is presented to support the practical findings.

High-precision frequency estimator by using discrete Fourier transform and asymmetric discrete time Fourier transform samples

Fast and accurate frequency estimation is significant for instrumentation and measurement. A sinusoid frequency estimator using discrete Fourier transform (DFT) is presented. DFT is implemented on the sinusoid and the maximum DFT bin is sought out to obtain the coarse estimate. Different from all the existing methods, two asymmetric discrete-time Fourier transform (DTFT) samples situated at arbitrary positions on the same side of the maximum DFT bin are employed to get the fine estimate. The theoretical mean square error is analyzed. To evaluate the estimation performance, the presented estimator is compared with the Cramer-Rao lower bound (CRLB) and state-of-art estimators through computer simulations. Simulation results demonstrate that the presented algorithm is closer to the CRLB compared with the competing methods when the signal-to-noise ratio (SNR) varies in a large range and is unbiased at high SNR.

Investigation of harmonic and inharmonic domain wall oscillation by sinusoidal magnetic field in the notched Permalloy nanowire using micromagnetic approach

In this work, the harmonic and inharmonic domain wall (DW) oscillations by sinusoidal magnetic field in double triangular notched Permalloy nanowires were investigated by micromagnetic simulation. The simulation results show the DW resonant frequencies were linearly related to the induced field frequency. It is shown that in the wire thickness of 2.5 ​nm, there is a minimum value of sinusoidal field frequency so that the DW can be harmonically oscillating as the induced magnetic field. Below the certain value, the DW will be moving out of the notch as depinning process occurs. In the higher frequency, the DW resonant frequency fluctuates and the phase-lag is larger, so that the DW oscillates inharmonically with the injected sinusoidal field and the resonant frequency decreases significantly. These phenomena could be understood by the slight change of the DW approximated mass as its position shifted around notch area. Therefore, the understanding of DW structures and dynamics under the effect of oscillating magnetic field could be a consideration on the selection of optimized nanowire geometries in the development of the domain wall-based memory storage system.

Numerical study of periodically heated wall effect on natural convection in an enclosure

The present numerical study focuses on sinusoidal heating and aspect ratio effects on heat flow of free convection of fluid inside the enclosure. The side walls are maintained at ambient temperature and the middle horizontal wall that divides the enclosure evenly is heated to sinusoidal temperature and the other horizontal walls are adiabatic. The numerical solution of the transport equations is done by the finite difference method to determine the heat transfer and thermal penetration with respect to aspect ratio, sinusoidal frequency and Rayleigh number. The numerical results of heat and fluid flow in the range of controlled governing parameters such as Rayleigh number (Ra = 105), sinusoidal frequency (1 ⩽N⩽ 4 ) and aspect ratio (0.2 ⩽A⩽ 4) are analysed in terms of streamlines, isotherms, heat penetration length and Nusselt number. It has been found that the 100% thermal penetration in the upper part of the enclosure of the aspect ratio A = 1 is obtained on continuous heating, while in the lower section, the maximum thermal penetration is limited to 98%, which is obtained on non-continuous heating in the enclosure of aspect ratio A = 0.2, 0.5.

Breakdown voltages in thrust bearings: Behavior and Measurement

This paper investigates breakdown characteristics in the bearings of variable speed electric drive trains. The analyses reveal that breakdown phenomena previously known from high-voltage technology appear to also occur in the bearing contact, though at significantly lower voltages. By loading the bearing with AC voltage of different frequencies at various mechanical load points, five states, which range from partial discharge through arc discharge to a completely conductive channel, emerge. Consistent with the concept that the magnitude of the breakdown voltage depends on the lubricant film height, the contact force, and the frequency of the AC voltage, a thicker lubricant film results in a higher breakdown voltage, analogously to a capacitor with a larger plate spacing, which requires a higher potential difference to be punctured. Furthermore, the sinusoidal frequency of the AC load correlates with the breakdown voltage. The breakdown tends to occur earlier at low frequencies, which is illustrated by the fact that at low frequencies, capacitive behaviour can only be observed at higher speeds, i.e., at a larger lubrication gap, while no voltage can be built up over the bearing at lower speeds. An increase of the contact force for the same lubricant film height lowers the breakdown voltages. The reduction of the breakdown voltage by the contact force may result from an increase of the relative permittivity of the lubricant with higher pressure and likewise of the contact area; the increased area may also increase the number of surface-roughness peaks where an increase in the electric field occurs.

Comparison between Two Time Synchronization and Data Alignment Methods for Multi-Channel Wearable Biosensor Systems Using BLE Protocol

Wireless wearable sensor systems for biomedical signal acquisition have developed rapidly in recent years. Multiple sensors are often deployed for monitoring common bioelectric signals, such as EEG (electroencephalogram), ECG (electrocardiogram), and EMG (electromyogram). Compared with ZigBee and low-power Wi-Fi, Bluetooth Low Energy (BLE) can be a more suitable wireless protocol for such systems. However, current time synchronization methods for BLE multi-channel systems, via either BLE beacon transmissions or additional hardware, cannot satisfy the requirements of high throughput with low latency, transferability between commercial devices, and low energy consumption. We developed a time synchronization and simple data alignment (SDA) algorithm, which was implemented in the BLE application layer without the need for additional hardware. We further developed a linear interpolation data alignment (LIDA) algorithm to improve upon SDA. We tested our algorithms using sinusoidal input signals at different frequencies (10 to 210 Hz in increments of 20 Hz-frequencies spanning much of the relevant range of EEG, ECG, and EMG signals) on Texas Instruments (TI) CC26XX family devices, with two peripheral nodes communicating with one central node. The analysis was performed offline. The lowest average (±standard deviation) absolute time alignment error between the two peripheral nodes achieved by the SDA algorithm was 384.3 ± 386.5 μs, while that of the LIDA algorithm was 189.9 ± 204.7 μs. For all sinusoidal frequencies tested, the performance of LIDA was always statistically better than that of SDA. These average alignment errors were quite low-well below one sample period for commonly acquired bioelectric signals.

Research on design and mechanical behavior of a new horizontal connection device of prefabricated shear wall

The mechanical properties of the connection joints/horizontal joints of the fabricated shear wall structure play a vital role in the fabricated structure. In order to improve the seismic performance of the fabricated shear wall structure, a new type of assembled shear wall horizontal connection device is designed and developed based on the principle of energy dissipation in this study. Two horizontal connection devices with different bolt number are designed and manufactured. The device comprises of high-strength bolts and Q345 steel. The dynamic mechanical behaviors are tested for the horizontal connection device under different sinusoidal loading frequencies. The influence laws of different bolt preload, loading frequencies and bolt numbers are explored on the mechanical properties of the device. The effect of friction temperature rise on the mechanical properties of the device is investigated. The experimental results indicate that the device can not only ensure the reliable connection of the structure, but also dissipate significant seismic energy by the internal friction of the device, so as to effectively reduce the seismic response of the structure and protect the main structure. Additionally, the energy dissipation capacity and secant stiffness of the device is proportional to the bolt preload, but the equivalent damping ratio is independent of the preload; the mechanical properties of the horizontal connection device hardly depend on the loading frequency; the increase of the bolt number can considerably enhance the energy dissipation of the device; Both the preload and loading frequency are important factors affecting the temperature rise of the device, but the temperature change has little effect on its mechanical behaviors.

Ivrr-PPG: An Illumination Variation Robust Remote-PPG Algorithm for Monitoring Heart Rate of Drivers

Heart rate can be accurately measured by Remote PhotoPlethysmoGraphy (rPPG) in stable illumination and noise-controlled environments such as indoors. However, heart rate measure in automotive scene is still faced with several challenges since the lighting illumination in the cab often changes dramatically. To address such issues, a novel method named Illumination Variation Robust Remote-PhotoPlethysmoGraphy (Ivrr-PPG) is proposed for monitoring the heart rate of drivers during on-road driving. The prototype is based on a commercial off-the-shelf imaging system, which includes a monochrome camera with 940 nm narrowband NIR filter and two 940 nm NIR active light sources to collect real-time video of drivers. Based on a dichromatic model, the core idea of our method is to model the non-linear relationship between illumination changing and the rPPG signal. This paper also proposed to use a background region to sense the illumination changing and consequently suppress its impact on the pulse signal. A singletone sinusoidal signal-based frequency estimation method is then used to compute the heart rate. Experimental results conducted on four different on-road driving scenarios show that the Ivrr-PPG significantly outperforms the state-of-the-art single-channel narrowband NIR algorithms.

Pulsed Active Sonar Using Generalized Sinusoidal Frequency Modulation for High-Speed Underwater Target Detection and Tracking

Pulsed Active Sonar Using Generalized Sinusoidal Frequency Modulation for High-Speed Underwater Target Detection and Tracking

Waveform design and signal processing method for integrated underwater detection and communication system

AbstractFor the integrated system of underwater detection and communication, an emitted waveform should satisfy both detection and communication requirements. The signal processing method at the receiving end must also accomplish target detection and communication accordingly. This study uses a generalised sinusoidal frequency modulated (GSFM) waveform with a carrier to ensure detection performance. At the same time, the communication information encoding with Gaussian Minimum Shift Keying is modulated to the GSFM signal for communication purposes. Unlike previous work, an improved Blind Source Separation algorithm is utilised at the receiving end, which is better adapted to waveform separation and processing in the underwater time‐varying unknown environment. The analysis of detection probability, peak‐to‐average ratio, and signal processing results show that the proposed waveform and corresponding signal processing scheme can effectively meet the need for integrated underwater detection and communication system.

Investigation of an M-Sequence based impedance spectrum acquisition method for lithium-ion batteries from the engineering application perspective

Electrochemical impedance spectroscopy (EIS) is frequently reported to be used in mechanism analysis, state estimation, and fault diagnosis of lithium-ion batteries. For a long time, EIS has been measured in the laboratory using carefully designed equipment, which has the problem of long measurement time and is not convenient for field applications. How to obtain broadband electrochemical impedance spectroscopy quickly and accurately has become a key issue. Being different from the traditional impedance measurement method based on sinusoidal frequency sweep, in this paper, we obtain the EIS by using Fast Fourier Transform (FFT) for maximum length sequence (M-Sequence) excitation current and corresponding response voltage. M-sequence excitation can be generated by fast responding charging and discharging equipment, etc., with higher flexibility. To guide the engineering application, for the first time, the effect of M-Sequence parameters and sampling frequency on the impedance calculation results are investigated through experiments. A series of experimental results show that when given the frequency range to be measured, the parameters of M-Sequence and the sampling frequency can be determined to calculate the EIS quickly and accurately.

An electromagnetic energy harvester for applications in a high-speed rail pavement system

Energy harvesting from ambient environment is one of the effective solutions to supply power for low power electronic devices. There are still some challenges such as poor space utilization and low power density for pavement energy harvesters. In this paper, an electromagnetic energy harvester with the double rockers is proposed to harvest the human footstep energy from high-speed rail pavement environment. Combined with two one-way bearings, the proposed double-rocker structure converts up and down motion of plate into a unidirectional rotation motion of the shaft. As the effect of the inertia flywheel, the velocity attenuation of the shaft of generator is slowed down. The dynamic model of the energy harvester with the engagement and disengagement phase is explored. Moreover, the input force and the angular velocity are simulated under the input of the various sinusoidal displacements and frequencies. The simulation and experimental results show that it can obtain the maximum output power of 466.6 mW under the vibration frequency of 5 Hz and the displacement of 10 mm. Further, the inertia flywheel can enhance the system stability and achieve the improvement of average output power by 49.45 % compared with no flywheel system. A pavement block with four energy harvesters is assembled and the actual field test proves it can obtain the maximum voltage of 54.4 V and the output power of 1.034 W, which proves the proposed electromagnetic energy harvester has great potential to achieve self-powered monitoring system and power for the low power electronic devices in high-speed rail environment.

Invention of a contactless voltage relay with an adjustable reset ratio

The purpose of this article is to apply the relay effect observed in semiconductor circuits to create a contactless relay voltage with an adjustable return coefficient, connected in one device sensitivity to the input voltage and switching of powerful loads to high currents. A dynamic circuit is investigated, consisting of an adjustable semiconductor, in series with a parallel circuit of a capacitor and a resistor, which is one of the parts of the proposed relay device with a sinusoidal frequency of voltage fluctuations on the load. To study the operating modes and analyze the device circuits, it is recommended to use numerical methods using computer technology.The principle of operation and experimental characteristics of the developed device are presented.

Low-Speed Rotating Restart and Speed Recording for Free-Running Sensorless IPMSM Based on Ultrahigh Frequency Sinusoidal Wave Injection

In the low-speed operating range of sensorless interior permanent magnet synchronous motor (IPMSM), this article proposed an ultrahigh frequency (UHF) sinusoidal voltage injection method supplied by the control power supply, and the corresponding signal injection and detection system topology are designed. The proposed method replaces the traditional high-frequency injection method to continuously detect the rotor position by injecting UHF sinusoidal detection voltage into the three-phase motor windings during the main power supply (MPS) down, thereby avoiding the loss of rotor polarity information. When the MPS is restored, there is no need to wait for the convergence process of the position observer and the rotor polarity determination process. The sensorless IPMSM can immediately resume normal operation at low speed. For applications with low load inertia, the proposed method improves the rapidness of rotating restart, realizes zero-wait operation after MPS is restored, and reduces the speed drop during the power down. For electric vehicle (EV) applications, the proposed method meets the requirements of EVs event data recorder to continuously record the motor speed when the MPS is <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> . The experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed method.

Perception Accuracy of a Multi-Channel Tactile Feedback System for Assistive Technology.

Assistive technology uses multi-modal feedback devices, focusing on the visual, auditory, and haptic modalities. Tactile devices provide additional information via touch sense. Perception accuracy of vibrations depends on the spectral and temporal attributes of the signal, as well as on the body parts they are attached to. The widespread use of AR/VR devices, wearables, and gaming interfaces requires information about the usability of feedback devices. This paper presents results of an experiment using an 8-channel tactile feedback system with vibrators placed on the wrists, arms, ankles, and forehead. Different vibration patterns were designed and presented using sinusoidal frequency bursts on 2, 4, and 8 channels. In total, 27 subjects reported their sensation formally and informally on questionnaires. Results indicate that 2 and 4 channels could be used simultaneously with high accuracy, and the transducers' optimal placement (best sensitivity) is on the wrists, followed by the ankles. Arm and head positions were inferior and generally inadequate for signal presentation. For optimal performance, signal length should exceed 500 ms. Furthermore, the amplitude level and temporal pattern of the presented signals have to be used for carrying information rather than the frequency of the vibration.