Showing papers on "Fundamental frequency published in 2018"

Crepe: A Convolutional Representation for Pitch Estimation

Abstract: The task of estimating the fundamental frequency of a monophonic sound recording, also known as pitch tracking, is fundamental to audio processing with multiple applications in speech processing and music information retrieval. To date, the best performing techniques, such as the pYIN algorithm, are based on a combination of DSP pipelines and heuristics. While such techniques perform very well on average, there remain many cases in which they fail to correctly estimate the pitch. In this paper, we propose a data-driven pitch tracking algorithm, CREPE, which is based on a deep convolutional neural network that operates directly on the time-domain waveform. We show that the proposed model produces state-of-the-art results, performing equally or better than pYIN. Furthermore, we evaluate the model's generalizability in terms of noise robustness. A pre-trained version of CREPE is made freely available as an open-source Python module for easy application.

CREPE: A Convolutional Representation for Pitch Estimation

Abstract: The task of estimating the fundamental frequency of a monophonic sound recording, also known as pitch tracking, is fundamental to audio processing with multiple applications in speech processing and music information retrieval. To date, the best performing techniques, such as the pYIN algorithm, are based on a combination of DSP pipelines and heuristics. While such techniques perform very well on average, there remain many cases in which they fail to correctly estimate the pitch. In this paper, we propose a data-driven pitch tracking algorithm, CREPE, which is based on a deep convolutional neural network that operates directly on the time-domain waveform. We show that the proposed model produces state-of-the-art results, performing equally or better than pYIN. Furthermore, we evaluate the model's generalizability in terms of noise robustness. A pre-trained version of CREPE is made freely available as an open-source Python module for easy application.

Manipulation of polarisations for broadband terahertz waves emitted from laser plasma filaments

Abstract: Polarization control of broadband terahertz waves is essential for applications in many areas, such as materials science, medical and biological diagnostics, near-field communications and public securities. Conventional methods for polarization control are limited to narrow bandwidth and often with low efficiency. Here, based on theoretical and experimental studies, we demonstrate that the two-colour laser scheme in gas plasma can provide effective control of elliptically polarized terahertz waves, including their ellipticity, azimuthal angle and chirality. This is achieved with a circularly polarized laser at the fundamental frequency and its linearly polarized second harmonic, a controlled phase difference between these two laser components, as well as a suitable length of the laser plasma filament. Flexible control of ellipticity and azimuthal angle is demonstrated with our theoretical model and systematic experiments. This offers a unique and flexible technique on the polarization control of broadband terahertz radiation suitable for a wide range of applications. Broadband terahertz (THz) pulses are generated from a laser filament with a near-infrared laser at the fundamental frequency and its second harmonic. The azimuthal angle and ellipticity of the THz pulses are arbitrarily controlled by the two lasers.

Sliding-Mode Observer Based Voltage-Sensorless Model Predictive Power Control of PWM Rectifier Under Unbalanced Grid Conditions

Abstract: A sliding-mode grid voltage observer (SMGVO) is proposed and experimentally verified in this paper for voltage-sensorless operation under an unbalanced network. The fundamental positive sequence component (FPSC) and fundamental negative sequence component (FNSC) are inherently separated in the observer without employing any additional filters. Due to embedded filtering effect, high frequency chattering and harmonic ripples can be well suppressed. Additionally, dc components can be completely rejected. As a result, dc offset would not cause fundamental frequency oscillations in magnitude and frequency of the estimated FPSC and FNSC. Owing to the predictive ability of SMGVO, one-step delay can be directly compensated using state variables in the observer. By combining estimation and prediction into one stage, the designed SMGVO turns out to be a compact solution for finite-control-set model predictive power control without voltage sensors. Theoretical proof is derived to verify that FPSC and FNSC can be accurately estimated and separated. Experimental results obtained from a two-level PWM rectifier confirm the effectiveness of the whole control system.

An Adaptive Periodic-Disturbance Observer for Periodic-Disturbance Suppression

Abstract: Repetitive operations are widely conducted by automatic machines in industry. Periodic disturbances induced by the repetitive operations must be compensated to achieve precise functioning. In this paper, a periodic-disturbance observer (PDOB) based on the disturbance observer (DOB) structure is proposed. The PDOB compensates a periodic disturbance including the fundamental wave and harmonics by using a time-delay element. Furthermore, an adaptive PDOB is proposed for the compensation of frequency-varying periodic disturbances. An adaptive notch filter is used in the adaptive PDOB to estimate the fundamental frequency of the periodic disturbance. Simulations compare the proposed methods with a repetitive controller and the DOB. Practical performances are validated in experiments using a multiaxis manipulator. The proposal provides a new framework based on the DOB structure to design controllers using a time-delay element.

Design of Ultrawideband High-Efficiency Extended Continuous Class-F Power Amplifier

Abstract: Total bandwidth of existing wireless communication technologies covers a wide frequency range of over one octave. But most existing power amplifier configurations cannot meet this requirement while at the same time maintaining a high efficiency. Therefore, a new structure that can achieve multioctave bandwidth is proposed in this paper together with the design methodology. The difficulty in realizing a bandwidth larger than one octave lies in the overlapping of fundamental and harmonic frequencies. Regarding this problem, the continuous class-F mode is extended to allow a resistive second harmonic impedance, rather than the pure reactive one. With the relaxed design requirements and overlapping design space of fundamental and second harmonic frequencies, harmonic tuning and fundamental frequency matching networks can be designed separately. More importantly, broadband matching for fundamental frequencies can be implemented simply by considering only three fundamental frequency points using the multiple frequencies matching method. To verify the validity of the proposed methodology, a multioctave power amplifier was designed, fabricated, and measured. Measured results verify a wide bandwidth of 128.5% from 0.5 to 2.3 GHz. Over this frequency range, drain efficiency was larger than 60% with output power greater than 39.2 dBm and large signal gain larger than 11.7 dB.

Vibration analysis of rotating nanobeam systems using Eringen's two-phase local/nonlocal model

Abstract: Due to the inability of differential form of nonlocal elastic theory in modelling cantilever beams and inaccurate results for some type of boundaries, in this study, a reliable investigation on transverse vibrational behavior of rotating cantilever size-dependent beams is presented. Governing higher order equations are written in the framework of Eringen's two-phase local/nonlocal model and solved using a modified generalized differential quadrature method. In order to indicate the influence of different material and scale parameters, a comprehensive parametric study is presented. It is shown that increasing the nonlocality term leads to lower natural frequency terms for cantilever nanobeams especially for the fundamental frequency parameter which differential nonlocal model is unable to track appropriately. Moreover, it is shown that rotating speed and hub radius have a remarkable effect in varying the mechanical behavior of rotating cantilever nanobeams. This study is a step forward in analyzing nanorotors, nanoturbines, nanoblades, etc.

Study on self-adjustable tuned mass damper with variable mass

Abstract: Summary Tuned mass dampers (TMDs) represent a quite mature technology for controlling human-induced vibrations of footbridges, when they are tuned to the primary structure's fundamental frequency. However, the TMD is very sensitive to even a small change in the tuning ratio. This paper proposes a novel TMD named self-adjustable variable mass TMD (SAVM-TMD), which is capable of varying its mass and retuning its frequency on the basis of the acceleration ratio between the primary system and the TMD. The accelerations are obtained from two acceleration sensors, and the frequency adjustment is achieved by using a microcontroller and actuating devices. The acceleration ratio limit value should be set in the microcontroller firstly, and when the adjustment begins, the microcontroller will retune the TMD to a reasonable frequency region, under a specific harmonic excitation. The SAVM-TMD can be regarded as a passive control device capable of adjusting its frequency. The performance of SAVM-TMD is studied via both experimental studies and numerical simulations under different pedestrian excitations. It is found that the SAVM-TMD is effective in reducing the response and improving the equivalent damping ratio of the primary system when the structural frequency changes, with little power consumption. The results obtained from the experimental studies and the numerical simulations agree with each other very well. More pedestrian vibration situations are studied in the numerical simulations, and the results also show that the SAVM-TMD has excellent performance in controlling human-induced vibrations.

Diversity in pitch perception revealed by task dependence

Abstract: Pitch conveys critical information in speech, music, and other natural sounds, and is conventionally defined as the perceptual correlate of a sound's fundamental frequency (F0). Although pitch is widely assumed to be subserved by a single F0 estimation process, real-world pitch tasks vary enormously, raising the possibility of underlying mechanistic diversity. To probe pitch mechanisms we conducted a battery of pitch-related music and speech tasks using conventional harmonic sounds and inharmonic sounds whose frequencies lack a common F0. Some pitch-related abilities - those relying on musical interval or voice recognition - were strongly impaired by inharmonicity, suggesting a reliance on F0. However, other tasks, including those dependent on pitch contours in speech and music, were unaffected by inharmonicity, suggesting a mechanism that tracks the frequency spectrum rather than the F0. The results suggest that pitch perception is mediated by several different mechanisms, only some of which conform to traditional notions of pitch.

Study of Wireless Power and Information Transmission Technology Based on the Triangular Current Waveform

Abstract: Wireless power and information transmission (WPIT) technology can realize simultaneous wireless transmission of power and information. In this paper, the fundamental component of the triangular current waveform is employed to transfer power, and its third-order harmonic component is selected to transfer information. The Fourier decomposition method is conducted to analyze the triangular current waveform; two equivalent circuit models of the proposed WPIT system are established based on the relationship between the fundamental component and the third-order harmonic component. Harmonic components have an enlargement effect on the deviation of the fundamental frequency; this feature is used to realize the weakly coupled control between the information transmission and the efficiency of wireless power transfer. Based on the proposed harmonic communication method, the transient process and the maximum communication speed of the circuit are discussed. To achieve the high signal-to-noise ratio (SNR) communication, different space positions of the signal receiving winding are compared. Experimental results show that the proposed method provides a new solution for designing the WPIT system.

Doubly Enhanced Second Harmonic Generation through Structural and Epsilon-near-Zero Resonances in TiN Nanostructures

Abstract: Enhancing the nonlinear frequency conversion efficiency at the nanoscale is important for on-chip communication, information processing and sensing. Plasmonic nanostructures can significantly enhance the nonlinear signal due to localized surface plasmon (LSP) resonance, that is, localized electric field enhancements. Ideally, a double resonance occurs, in which both the excitation and the harmonic wavelengths are enhanced, but this is restricted by the available modes. It has been recently shown that thin films of epsilon-near-zero (ENZ) materials can also enhance optical nonlinear effects if excited at the ENZ wavelength. Here, we report the first demonstration of a new mechanism to enhance the second harmonic generation (SHG), combining a structural LSP resonance at the fundamental frequency, and the material ENZ resonance at the second harmonic frequency. We show that when both resonances are present, the SHG is substantially enhanced. With its refractory nature and CMOS compatibility, our results show...

Fast Amplitude Estimation of Harmonics Using Undecimated Wavelet Packet Transform and Its Hardware Implementation

Abstract: Accurate and fast estimation of time-varying harmonics are essential requirements for online monitoring, analysis, and control of electrical power system. This paper presents a fast algorithm based on the undecimated wavelet packet transform (UWPT) to estimate the amplitude of fundamental and harmonic components of stationary as well as a time-varying power signal. The UWPT uses only one cycle of the fundamental frequency for precise measurement of time-varying harmonics while their amplitude has been determined accurately utilizing the time-invariant property of the UWPT. The robustness and accuracy of the proposed technique have been investigated on synthetic as well as experimental test signals using MATLAB tool. Further, the UWPT algorithm has also been implemented on the Xilinx Virtex-6 FPGA ML-605 board, using XSG/ISE design suite 14.2 and its performance, in terms of hardware accuracy, resource utilization as well as timing requirements have been tested using the experimental test signal.

Prediction and Evaluation of PWM-Induced Current Ripple in IPM Machines Incorporating Slotting, Saturation, and Cross-Coupling Effects

Abstract: This paper presents an improved analytical model for estimating the high-frequency current ripple of interior permanent magnet synchronous machines due to pulsewidth modulation (PWM) switching. The proposed model accounts for the impact of slotting effect, magnetic saturation, and cross-coupling between the $d$ - and $q$ -axis. The model is subsequently used to investigate several factors that influence the PWM-induced current ripple. These include the PWM switching frequency, fundamental frequency (i.e., machine speed), dc-bus voltage, current control angle (i.e., γ angle), and the excitation current amplitude (i.e., saturation level). Experiments have been conducted to verify the analytical prediction results. These results show that the analytical model can predict the PWM-induced current ripple waveshape very well for many operating conditions and accurately estimate its rms value over a complete fundamental period.

Acoustic communication in fishes: Temperature plays a role

Abstract: Correspondence Friedrich Ladich, Department of Behavioural Biology, University of Vienna, Vienna, Austria. Email: friedrich.ladich@univie.ac.at Abstract Temperature affects peripheral and central mechanisms of signal production and detection in ectothermic animals. This study reviews for the first time the effects of temperature on acoustic communication in fishes and analyses whether changes in sound properties are coupled to changes in auditory sensitivities. Effects of temperature on sound production have been studied in approximately one dozen families of teleosts. Calling activity increased or was unaffected by temperature, in the latter case probably because seasonal, daily and lunar rhythms also influence mating behaviour and calling. Sound characteristics (pulse repetition rate, fundamental frequency) are positively correlated with temperature if pulses are directly based on sonic muscle contractions. In fishes possessing other sonic mechanisms, the dominant frequency of their pulsatile pectoral sounds may increase as well. Auditory sensitivities were mainly determined in otophysines, which possess enhanced hearing abilities. Studies revealed that hearing increased with temperature, in particular at higher frequencies. We know close to nothing about whether temperaturedependent changes in sound characteristics are coupled to changes in auditory sensitivity or mate choice. Female midshipman toadfish appear to choose males based on call frequency, which varies with temperature. Future studies need to address several topics: (i) temperature effects on sound production have to be separated from other sources of variation; (ii) effects on hearing need to be studied in many more taxa; (iii) potential negative effects of global warming on acoustic communication (because of temperature coupling) need to be investigated because fish constitute a major source of protein for humans.

Design of an advanced PLL for accurate phase angle extraction under grid voltage HIHs and DC offset

Abstract: The presence of direct current (DC) offset and harmonics–interharmonics (HIHs) in grid voltage input signal of phase-locked loop (PLL) results in inaccurate controller response. The inaccuracies are due to the low- and high-frequency oscillations that appear in the PLL estimated phase, amplitude and frequency. The suppression of fundamental frequency oscillations caused by DC offset (DO) in the input voltage signal must be carried out without compromising the dynamic response of the system. The use of low-pass filters, for example, results in undesirable, slow response. This study proposes an accurate and fast decoupling of fundamental frequency oscillations using a mathematic-cancellation decoupling cell. Higher-frequency oscillations generated by HIHs are eliminated by a different harmonic compensation network (HCN) that is also proposed in this study. The performance of conventional techniques is limited because they eliminate only specifically selected harmonics. The proposed PLL, however, eliminates any number of HIHs present in the grid with the least computational complexity and without any prior knowledge. Furthermore, its advanced features provide accurate synchronisation under any abnormal grid condition at the lowest computational complexity when compared with the existing state-of-the-art PLLs. The advanced performance of the proposed HIHDO-PLL is verified through simulation and experimental results.

Hybrid Fractional Repetitive Control for Magnetically Suspended Rotor Systems

Abstract: This paper investigates a hybrid fractional repetitive control (HFRC) scheme for magnetically suspended rotor systems to suppress harmonic current caused by mass imbalance and sensor runout. With parallel structure, HFRC consists of a frequency-adaptive dual-mode repetitive controller (DMRC) and a phase-shift notch filter. By introducing fractional delay filters, the proposed DMRC provides frequency adaptability to eliminate odd and even harmonics independently at fixed sampling rate. Its delay time is halved compared with the conventional repetitive control scheme, and the control gains can be weighted to ameliorate system dynamic response according to harmonics distribution. Moreover, as the domination of control current, fundamental frequency current is additionally rejected by the notch filter; thus, achieving smaller overshoot and faster suppression performance. An improved phase compensator is designed in HFRC to expedite current convergence rate while stabilizing the overall system. Experimental results on a magnetically suspended flywheel demonstrate the advantages of the proposed method.

Single-Channel Speech Enhancement With Phase Reconstruction Based on Phase Distortion Averaging

Abstract: Speech enhancement has been widely investigated for several decades, but by modifying only the amplitude spectrum of a speech signal, ignoring the phase spectrum, which has been regarded as an unimportant feature. However, it was recently reported that the phase spectrum plays an important role in speech quality and intelligibility. In this paper, we propose a phase reconstruction method based on harmonic enhancement using the fundamental frequency and phase distortion feature. This feature is known to show fluctuations in the phase spectrum with respect to time and frequency. We estimate the speech phase spectrum by considering the relationship between harmonic phase spectra. Experimental evaluations indicate that the proposed phase reconstruction method improves speech quality in various noisy environments.

Free vibration characteristics of stiffened plates

Abstract: The free vibration characteristics, such as fundamental frequency and mode shape of stiffened plates employing standard finite element analysis, are investigated in this paper. The parametric study is presented for free vibration characteristics of stiffened plates with various parameters, such as type, orientation and number of stiffeners, boundary conditions and aspect ratio of plates and stiffener depth to plate thickness ratio. Typical mode shapes are also presented for clamped square eccentrically stiffened plates. Finally, design charts with non-dimensional parameters are proposed to determine the fundamental frequency of commonly adopted clamped stiffened plates in construction. These charts will be very much useful for designers for obtaining the fundamental frequencies of the stiffened plates of different dimensions without doing much complicated analysis or using standard computer codes.

A Fundamental Frequency Sorting Algorithm for Capacitor Voltage Balance of Modular Multilevel Converter With Low-Frequency Carrier Phase Shift Modulation

Abstract: This paper proposes a fundamental frequency sorting algorithm for balancing the floating capacitors in modular multilevel converters with low-frequency carrier phase shift modulation. The relationship between the driving pulses and submodules (SMs) is rebuilt in every fundamental period by sorting the voltage increments and present voltages. Besides, an improved and simplified strategy is proposed to predict the charging abilities of the driving pulses, so as to avoid sorting the voltage increments. Based on the proposed method, the switching frequency of each power device and the carrier frequency are identical, which reduces the operational losses for applications regarding high power. At the same time, the sorting frequency is as low as the fundamental frequency, which alleviates a large amount of computational cost, and the necessity to measure arm currents is omitted. In this case, the arm current sensors are eliminated, and simplified communication among the central controller and the local ones is set up. Finally, a three-phase 1-MVA simulation platform with 120 SMs and a down-scaled 6-kVA experimental prototype with 48 SMs are constructed to validate the proposed approach.

Compact Ring Slot Antenna With Harmonic Suppression

Abstract: Harmonic suppression antennas are widely used in the microwave power transmission and active antenna systems. In this letter, a square ring slot loaded with two side slots is constructed as the radiating element. Meanwhile, a bottom transverse slot orthogonal to the microstrip feedline is introduced as the harmonic suppression unit. In fact, the part of microstrip feedline that extends into the slot ring also has an inhibitory effect on the harmonics. In this way, a compact slot antenna with harmonic suppression is constructed. For the proposed antenna, the fundamental frequency and harmonic rejection can also be adjusted independently, so the antenna structure is easy to implement. The experimental results of the prototype antenna show that the designed antenna achieves good suppression for the second- and third-order harmonics.

Quasi-periodic aeroelastic response analysis of an airfoil with external store by incremental harmonic balance method

Abstract: This paper presents an investigation on the nonlinear aeroelastic system of an airfoil with external store by incremental harmonic balance (IHB) method. Besides solving limit cycle (LC) solutions, the IHB method is implemented to obtain quasi-periodic (QP) solutions by introducing multiple irreducible time scales. Steady state responses such as LC and QP oscillations obtained by the presented method are verified by numerical examples. One pair of Floquet multipliers for LC solutions first leave and then enter a unit cycle at complex conjugate values, indicating the existence of a secondary Hopf bifurcation and its reversal one. Along with the fundamental frequency of LC oscillation, an additional frequency arises at the secondary bifurcation, and finally disappears at the reversal bifurcation. The appearance and disappearance of the irreducible frequency cause the steady state responses changing from LC to QP and back to LC oscillation.

A New DC-Offset Removal Method for Distance-Relaying Application Using Intrinsic Time-Scale Decomposition

Abstract: This paper presents a new adaptive method based on the intrinsic time-scale decomposition (ITD) tool for suppressing the decaying dc component effect on phasor estimation. The ITD decomposes a non-stationary fault signal into a proper rotation component (PRC) and a monotonic trend signal. The PRC is the fundamental frequency component, which is used by the discrete Fourier transform (DFT) to estimate the phasor, and the monotonic trend signal is the decaying dc component. The combination of the ITD and the DFT is a simple accurate method for phasor estimation that is applicable to protection schemes with the minimum sampling rate and also to the off-nominal power system frequency. Three types of data, i.e., mathematical, simulated, and real field fault, are examined to assess the performance of the proposed method. The obtained results confirm that the proposed method not only improves the distance relay operation, but it is not also affected by the change in the fault inception angle, fault type, fault location, power system frequency, and network topology. Furthermore, the method works both with a series compensated transmission line and a parallel transmission line.

Optimal lay-up design of variable stiffness laminated composite plates by a layer-wise optimization technique

Abstract: The optimal lay-up design for the maximum fundamental frequency of variable stiffness laminated composite plates is investigated using a layer-wise optimization technique. The design variables are ...