Sinusoidal Signal Research Articles

Rayleigh‐Taylor Instability Observed at the Dayside Magnetopause Under Northward Interplanetary Magnetic Field

AbstractUnder northward interplanetary magnetic field, periodical fluctuations with the period of 85 s have been observed by one of the Time History of Events and Macroscale Interactions during Substorms spacecraft at the dayside magnetopause when the solar wind dynamic pressure suddenly dropped. The observed magnetic field distortions, characterized by the compression of the main component as well as the flapping of the perpendicular components, are in line with the theoretical predictions of the Rayleigh‐Taylor (R‐T) instability excited at the magnetopause. With the convective electric field and the mean electric field removed, the perturbations in the electric field are identified as typical two sinusoidal signals with a 90° phase difference, consistent with previous prediction of the attendant electrostatic field arising from the R‐T instability. The transverse motions of the plasmas resulting from the electric drifting driven by the electrostatic field are observed both in pitch‐angle distributions and in distribution functions. The growth rate of the R‐T instability is about 43 s, implying that the instability has time to grow during the disturbances. Using the Gauss theorem, the calculated net charge density based on the electric field observation is one part of 27 compared to the totally observed plasma density, indicating that only a tiny fraction of the charge separates to set up the electrostatic field, which is due to a collective effect in the plasma.

A Control Scheme for a Quasi-Z Source Three-Phase Inverter

This paper presents a novel control scheme for a three-phase quasi-z source inverter (qZSI) using a capacitor voltage and input current-based sinusoidal pulse width modulation (SPWM) technique. The proposed scheme combines the advantages of both qZSI and SPWM techniques to achieve improved performance. The SPWM technique utilizes a sinusoidal modulation signal, which is compared with a high-frequency triangular carrier wave and two shoot-through (ST) references to determine the switching states for the three-phase qZSI. The positive and negative ST references are obtained from the capacitor voltages and input current, allowing for control of the DC bus voltage and ST states of the inverter. Additionally, the proposed control scheme generates the three-phase modulation signal through decoupling control in the dq reference frame. The detailed analysis of the control scheme includes its operating principle, transient state, steady-state responses, and the effects of parameter variations. Simulation studies are conducted using MATLAB/Simulink to assess the performance of the three-phase qZSI under the proposed control scheme. The simulation results demonstrate the effectiveness of the control scheme in terms of output voltage quality, DC bus voltage control, and robustness against reference variations. Overall, the proposed capacitor voltage and input current-based SPWM control scheme for the three-phase qZSI shows promising performance improvements and robustness, as confirmed through comprehensive simulation studies.

Relocking and Locking Range Extension of Partially Locked AMLL Cavity Modes with Two Detuned RF Sinusoids

Actively mode-locked fiber ring lasers (AMLLs) with loss modulators are used to generate approximately 100ps pulses with 100MHz repetition. RF detuning around the fundamental frequency, f0, causes a loss in phase lock (unlocking) of cavity modes and partial mode locking. Multiple RF inputs are shown, theoretically, to relock and extend the locking range of cavity modes in a detuned partially mode-locked AMLL. A custom-built Yb3+-doped AMLL with f0=26MHz, and operating wavelength of 1064nm, was used to experimentally verify the theoretical predictions. Two RF sinusoidal signals with constant phase and equal amplitude resulted in an extension of the range by Xn=6.4kHz in addition to the range Rn=14.34kHz with single input for the mode n=10. An increase in locking range was also observed for higher modes. Pulsewidth reduction to approximately 205ps from about 2ns was also observed in the AMLL.

Amplitude-frequency characteristics of the "structure–pile foundation" layered model

Taking into account the interaction between a structure and the soil bed during an earthquake is a vital task of the seismic resistance theory. Despite a large amount of research, there is no satisfactory solution of this problem at the time being. The "platform model" applied in engineering practice can be used only for homogeneous soil beds. However, the surface stratum of soil, as a rule, has a multilayer structure, in which each individual layer has its own physical and mechanical characteristics determining the resonant properties of the entire system. The standard methods of analysis do not take into consideration the heterogeneity and layered nature of a soil bed using the averaged stiffness characteristics, which does not allow evaluating the specific features of resonance processes during the joint oscillation of a building and its soil bed. In addition, the dynamic characteristics of soils have a rather high statistical variability even within the same layer, and this can significantly affect the distribution pattern of the resonant frequencies of the system.
 The present article is aimed at investigating the dynamic response of the “building – multilayer soil bed” system based on the analytical model of a horizontal layered medium.
 The following tasks were solved:
 – an analysis of a layered system under the action of a complex sinusoidal signal was carried out with regard to damping;
 – the amplitude-frequency characteristics were constructed both for individual layers and for the system as a whole;
 – the influence of the statistical variability of the velocity of transverse seismic waves propagation on the resonant frequencies of the layered system under consideration was assessed.
 The analytical methods for the solution of the wave problem of seismology were used.

Research on Hydro-pneumatic Suspension Test Bench Based on Electro-hydraulic Proportional Control

Compared with the traditional automotive suspension, hydro-pneumatic suspension has the characteristics of large energy storage ratio, nonlinear stiffness and can change the ground clearance of the vehicle body, which makes the vehicle have good ride comfort and handling stability during driving. In order to improve the performance of hydro-pneumatic suspension, it is necessary to design hydro-pneumatic suspension test bench for performance test. Aiming at the problem that the output signal of the mechanical test bench used in China is single and has large error, which is difficult to meet the performance test requirements of hydro-pneumatic suspension, a hydro-pneumatic suspension test bench based on electro-hydraulic proportional control is designed. Through AMESim/MATLAB joint system modeling and simulation, in the tracking comparison of sinusoidal signal, compared with the traditional PID control method, the fuzzy PID control method reduces the error by 56.8% and the lag time by 70%; Through the experimental analysis of hydro-pneumatic suspension elastic force characteristic diagram, indicator diagram and damping force velocity characteristic diagram, the error rate of the test bench in sinusoidal signal tracking experiment is less than 15%, which meets the test requirements of hydro-pneumatic suspension.

Optical Frequency Comb Generator Employing Two Cascaded Frequency Modulators and Mach–Zehnder Modulator

Optical frequency combs (OFCs) are extensively used in spectroscopy, range finding, metrology, and optical communications. In this paper, we propose a novel technique to achieve a flat OFC by serially cascading two frequency modulators (FMs) followed by a single-drive Mach–Zehnder modulator (MZM). The modulators are driven by a sinusoidal RF signal of frequencies fm, fm2, and 2 fm GHz, respectively. With our proposed approach (fm), an optical spectrum of 71 subcarriers spaced at 4 GHz is realized within a power fluctuation of ∼2 dB. The proposed method is also tested for fm = 16 GHz, showing that this approach can work in all scenarios with lower power fluctuations. In addition, we also studied the impact of the phase of the RF signal on the power variation of the OFC spectrum. A theoretical investigation of the ultra-flat spectrum generated by cascaded FMs and MZM is conducted, and the results of simulations support the findings. The simulation results demonstrate good performance, allowing for the application of our proposed approach in next-generation optical networks.

Random noise test of analog-to-digital converters

The random noise test of analog to digital converters recommended by the IEEE 1057 Standard for digitizing waveform recorders is studied. The heuristically derived expression presented for the estimation of the random noise standard deviation is experimentally validated. The standard suggests a triangular stimulus signal. Here we will show how to use a sinusoidal stimulus signal to carry out the test. The influence of stimulus signal offset and amplitude on the estimation error is also analyzed and an expression is presented to compute the minimum amplitude value that guarantees an upper bound on the estimator bias.

Feasibility of Using a Mobile Device to Identify the Axle Whine Noise in a Vehicle

This article investigates the feasibility of using the built-in microphones of mobile devices to diagnose axle whine noise in a vehicle. Three sound pressure measuring sensors or devices are selected. The first one is a high-end condenser microphone, which is calibrated during the measurements; this data is taken as a reference for the other devices. Then two different types of mobile devices are selected and relative calibrations are carried out. Measurements are first performed inside a hemi-anechoic room; artificially generated sinusoidal and random sound signals are played through a calibrated sound source and data is acquired with all devices. This setup is placed inside a vehicle cabin (for a non-running engine) and measurements are repeated. The onboard entertainment system of the vehicle is used as well in addition to the calibrated sound source. Measurements reveal that one of the mobile devices has superior performance when compared to the other one though calibration improves the performance of the latter. Finally, measurements are performed inside the vehicle cabin while the vehicle is being driven along a certain path to assess the diagnostic performance. The axle whine noise problem in two vehicles is successfully detected by employing an empirical mode decomposition process.

Analysis and Design of Direct Force Control for Robots in Contact with Uneven Surfaces

Robots executing contact tasks are essential in a wide range of industrial processes such as polishing, welding, debugging, drilling, etc. Force control is indispensable in these type of tasks since it is required to keep the interaction force (between the robot and the environment/surface) within acceptable values. In this paper, we present a methodology to analyze and to design the force control system needed to regulate the force as close as possible to the desired value. The proposed methods are presented using a widely used generic contact task consisting of exerting a desired force on the normal direction to the surface while a desired velocity/position is tracked on the tangent direction to the surface. The analysis considers environments/surfaces with certain uneven characteristics, i.e., not perfectly flat. The uneven characteristic is studied using ramp or sinusoidal signals disturbing the position on the normal direction to the surface, and we present how the velocity on the tangent direction is related with the slope of the ramp or the frequency of the sinusoidal disturbance. Then, we provide a method to design the force controller that keeps the force error within desired limits and preserves stability, despite the uneven surface. Furthermore, considering the relation between the disturbance (ramp or sinusoidal) and the tangent velocity, we present a method to compute the maximum velocity for which the task can be executed. Simulations exemplifying and verifying the proposed methods are presented.

Design of Cascaded Multilevel Inverter and Enhanced MPPT Method for Large-Scale Photovoltaic System Integration

The key goal of this effort is to develop an efficient control system for a three-phase cascaded H-bridge multilevel inverter powered by the photovoltaic (PV) system. The power for the system is generated through the use of PV modules, which serve as DC inputs for the cascaded H-bridge multilevel inverter. The authors aim to achieve a nearly sinusoidal signal at the voltage level and are specifically focused on minimizing the total harmonic distortion (THD) to the smallest possible value. Hence, an advanced N-level space vector modulation (SVM) is developed to ensure an appropriate control for the cascaded inverter. The aim is to design an effective control strategy to increase inverter efficacy and, thus, supply the best output quality. In addition, a robust approach to the maximum power point (MPP) tracking (MPPT) technique is developed based on an adaptive perturb and observe (P&O) algorithm to ensure superior tracking of the MPP. The developed algorithm eliminates 90% of the power curve area in the search space process and only maintains 10% of the area that includes the MPP. Each PV system employs its own improved MPPT control. The numerical results confirm that the enhanced P&O algorithm attains a precise response with superior efficiency and a fast response under the fast alteration of environmental conditions. Hence, the energy loss is reduced. The simulation results validate the effectiveness of this study, highlighting the high efficiency of the control strategy and the enhanced performance of the proposed scheme with lesser THD values.

MODELLING AND SIMULATION OF DYNAMIC PROCESSES OF PNEUMATIC LINES

The paper presents the simulation of dynamic processes of pneumatic lines using the program "SIMULINK" from the product " MatLab". Simulation is a process of forming, preparing and entering a mathematical model in a computational environment and obtaining the results of the calculations performed in this environment. The mathematical model of the pneumatic line to be simulated is according to previously presented equations. For the simulation of the dynamic processes, various real parameters of the dimensions and lengths of the pneumatic lines with the corresponding coefficients are introduced into the model. The simulation of the transient responses was carried out with stepwise variation and sinusoidal input signal supplied by the set point device and pneumatic line lengths of 1 m, 5 m and 10 m. The simulation output data were output to the interface in the form of graphs showing the dependence of the observed quantities, the input and output pressure through the pneumatic line, and the input and output flow rates. From the mathematical model and the experiments performed, it can be concluded that the transient responses in the simulations correspond to the dynamic processes of pneumatic lines of different lengths.

A New Performance Optimization Method for Linear Motor Feeding System

The linear motor feeding system is a typical electromechanical coupling system. Conventional characteristic analyses of electromechanical coupling often overlook the influence of flexible deformation in critical components of the linear motor feeding system. Moreover, when employing genetic algorithms to optimize servo system PID control parameters, slow convergence, nonconvergence, or premature convergence problems may arise. To address these issues, this paper proposes a new performance optimization method for a linear motor feeding system. The method uses a combination of “multi-body theory + finite element” to accurately account for the flexible deformation of critical components of the feeding system, establishes a rigid–flexible electromechanical coupling model of the linear motor feeding system, and optimizes the PID parameters of the established model with an improved adaptive genetic algorithm. Simulation results demonstrate that, when utilizing an adaptive genetic algorithm to optimize the rigid–flexible electromechanical coupling model and a control system model that disregards flexible body deformation, the system achieves stability in 0.02 s and 0.027 s with overshoots of 13% and 27%, respectively. These outcomes confirm the accuracy and importance of considering flexible body deformation in the optimization performance of a linear motor feeding system. At the same time, the time required to reach the steady state of the rigid–flexible electromechanical coupling model optimized by the adaptive genetic algorithm is shortened from 0.035 s to 0.02 s. The sinusoidal signal response curve of the optimized system does not exhibit any peak overshoot compared with that of the nonoptimized system, and the response speed is also faster. These results demonstrate the effectiveness of the rigid–flexible electromechanical coupling model optimized by the nonlinear adaptive genetic algorithm. The displacement response curves of the linear motor feeding system under different workbench loads are obtained through experiments and compared with those obtained from simulations to verify the established model and the correctness of the proposed method.

Frequency estimation for underwater CW pulse by interpolation on fractional Fourier coefficients based on amplitude ratio method

Fast and accurate estimation of sinusoidal signals plays an important role in many fields like communications, radar, sonar, etc. In underwater signal processing applications, sinusoidal signals usually take the form of CW pulses in most practical applications, therefore, zero-padding and duty-cycle show their great importance to the estimation of sinusoidal signals. In this paper, a high-precision estimation algorithm of sinusoidal signal is proposed, which combines amplitude ratio algorithm and fractional Fourier coefficient interpolation algorithm. The proposed algorithm uses the adjacent spectral line ratio algorithm instead of the Fourier coefficient maximum amplitude discrete spectral line search algorithm for coarse estimation, and modifies the traditional interpolation method. The proposed algorithm improves the Fourier coefficient interpolation algorithm by combining zero-padded signals to achieve the accurate frequency estimation for zero-padded sinusoidal signal. The performance of the algorithm is also in accordance with theoretical level for zero-padded signals, which is a great improvement over the frequency estimation algorithm for non-padded signals as well as the algorithm for zero-padding signals. The theoretical results are verified by extensive computer simulations which show that the proposed algorithm can both achieve better results for zero-padding cases and maintain comparable performance with competing algorithms for the non-padded signal. Therefore, the algorithm can be better applied to practical underwater detection or communication signals.

Decoupling control of radial 4 degree of freedom system of magnetic-liquid double suspension bearing based on generalized extended state observer.

As the novel suspension bearing, Magnetic-Liquid Double Suspension Bearing (MLDSB) is mainly supported by magnetic suspension and supplemented by a liquid hydrostatic bearing. Due to its great bearing capacity and stiffness, rapid response, great active control, and so on, MLDSB is suitable for medium speed heavy loads and has a large carrying capacity and high operating stability. In addition, the radial inertia coupling and gyroscopic coupling between radial 4-DOF control channels can reduce control precision, operation stability, and reliability of MLDSB. Therefore, a mathematical model of radial 4-DOF rotor-dynamics of MLDSB is established in this paper, and the inherent coupling mechanism is explored. Taking inertial coupling, gyroscopic coupling, and external disturbance loads as lumped disturbances, a decoupled controller based on Generalized Extended State Observer (GESO) is established. The influence of the GESO controller on the decoupling and control performance of radial 4-DOF control channels is simulated. The results indicate that the decoupling effect of the GESO controller is great. Under the action of step signal, the steady displacement, maximum displacement, adjustment time, and peak time of the rotor after decoupling are all reduced, among which the steady displacement and maximum displacement are the most obvious. Under the sinusoidal signal, the steady displacement and maximum displacement are reduced by 90%, which can effectively avoid the "gap-impact" fault. Under the pulse signal, the steady displacement, maximum displacement, adjustment time, and peak time are all reduced, among which the maximum displacement is the most obvious. The research in this paper can provide a theoretical reference for the stable support and decoupling control of MLDSB.

An All-Digital Background Calibration Technique for M-Channel Downsampling Time-Interleaved ADCs Based on Interpolation

An all-digital background calibration technique for gain, timing, and bandwidth mismatches in the time-interleaved analog-to-digital converter (TI-ADC) is presented in this brief. The proposed calibration technique employs an interpolation filter and a Hilbert filter to generate a reference sequence for each sub-ADC. Subsequently, adaptive filters are used to calibrate the mismatch errors, the coefficients of which are updated by the least mean square (LMS) algorithm. The advantage of the technique is that it only requires the output sequence of the TI-ADC without any additional information or extra reference channels. Moreover, it is effective for the M-channel TI-ADC sampling of single-tone, multi-tone, and wideband signals in any Nyquist Band. The frequency shifting is analyzed via filter bank theory, avoiding the complex signal introduction. The simulation for 4-channel TI-ADC with 5 sinusoidal input signals, shows that the proposed technique can improve the SNDR and SFDR by 37 dB and 54 dB, respectively.

Position Detection and Speed Recording Method for Power-Off IPMSM in Full-Speed Range Based on Ultrahigh Frequency Signal Injection

For the sensorless interior permanent magnet synchronous motor (IPMSM), this letter proposes a rotor position and speed recording method applied in full-speed range after the main power supply (MPS) is OFF. The proposed method injects ultrahigh-frequency (UHF) sinusoidal voltage into the motor windings after the motor is powered off, and then calculates the motor rotor position and speed in real time by detecting the RMS value of the UHF sinusoidal signals. Based on the UHF signal injection method designed for the low-speed region, this letter improves the injection and detection timing and optimizes the online calculation method of rotor position and speed. The proposed method can work only when there is no power supplied to the motor, and it is used solely for the purpose of recording. This letter implements the first inductance-based full-speed motor power-off rotor position detection and speed calculation. It breaks the cognitive limitation that the inductance-based rotor position detection method is only applicable to the low-speed region.

A COMMERCIAL-OFF-THE-SHELF FREQUENCY MODULATED CONTINUOUS WAVE RADAR FOR VITAL SIGN MONITORING

Objective: Radar systems are capable of retrieving remotely micro-movements with very high precision. Millimeter-wave radars are already used in several medical applications (e.g. sleep disorders, heart beat rate, patient monitoring) and have shown promising results towards a remote Doppler cardiogram or arterial pulse wave measurements techniques. In this work, we tested a 122 GHz commercial-off-the-shelf (COTS) Frequency Modulated Continuous Wave (FMCW) radar for vital (respiratory and cardiac) signals monitoring. This required the setting up of a very precise experimental bench and the investigation of a robust data processing procedure. Design and method: An experimental bench (see Figure 1-a) has been set up with a high precision Newport linear actuator: a small target can be then displaced with less than 3 μm accuracy. Such system can replicate the thorax displacements due to the respiratory and cardiac activity. Two different motions were simulated: a ‘large’ 8 mm displacement at 0.15 Hz (a.k.a. respiratory) and a ‘small’ 0.5 mm at 1 Hz (a.k.a. cardiac). Furthermore, a shaker system can be used to reproduce completely arbitrary movements, even from real acquired Electrocardiogram (ECG) data. In this case, however, a reference measurement system would be necessary to determine the accuracy. Results: A first measurement set was dedicated to evaluate the accuracy of the radar system: around 50 acquisitions for each type of displacements were carried out. The accuracy of the radar measurements results in the order of ∼10 μm (see Figure 2). A second measurement set tested the dynamic resolution: in this case, a 0.4 Hz sinusoidal signal and a 0.8 Hz pulsation mix were fed to the shaker system. The radar is capable of retrieving both signal signatures (see Figure 3), with errors due to the combination of sharp pulse rise and low radar sampling frequency Conclusions: We show that a COST radar is able to retrieve vital signs chest displacements with a good accuracy in both amplitude and dynamics, thus representing a valid option for a remotely continuous cardiovascular monitoring. Next objectives are In Vivo measurements with an in-house radar system and measurements of blood pulse waves.

A reliability study on the cumulative averaging method for estimating effective stimulus time in vibration studies.

Finding the reflex circuitry responsible for high-frequency vibration-induced muscle contraction takes work. The main challenge is to determine the effective stimulus time (EST) point at which continuous (sinusoidal) stimulation (i.e., vibration) triggers the reflex response. A novel "cumulated averaging method" has been previously proposed for estimating the EST point. In the current study, we aimed to test the reliability of the cumulated average method. We used five different whole-body vibration (WBV) frequencies in two experiments. The consistency between the EST points estimated from the first and second experiments was analysed with the intraclass correlation (ICC) and technical error of measurement (TEM). The ICC coefficient with 95% CI for the EST point estimation was 0.988 (0.950-0.997). The relative TEM was 1.3%. We concluded that the cumulated average method is highly reliable in estimating the effective stimulus time point for high-frequency continuous sinusoidal signals.

Development of a novel strategy based on in-process compensation of charge leakage for static force measurement by piezoelectric force sensors

Ordinary piezoelectric force sensors are only capable of measuring dynamic forces but not static forces because of the charge leakage due to the finite resistance of piezoelectric materials and charge amplifiers. This paper presents a new strategy for in-process compensation of charge leakage for force measurement with wide spectrum from static to dynamic realized by piezoelectric force sensors. The compensation is in-process operated based on the concept of dynamic accumulation. In order to improve the measurement accuracy and long-term stability by the compensation, the zero offset generated by normalization, bias current and temperature drift are all theoretically analyzed and experimentally validated. Measurement experiments of four different types of force signals, which contain static, triangular, sinusoidal and random force signals acting on the piezoelectric force sensor, are conducted to validate the proposed strategy. In addition, the effect of different time constant of the piezoelectric sensor under different applied forces on the compensated results is analyzed. Performance tests containing accuracy, resolution, span and bandwidth have been conducted. It is validated that the proposed method has high sensitivity of sub-millinewton, long-term stability and wide spectrum from static signal to dynamic measurement capabilities, which would provide an effective and precise method for micro force measurement and control in ultra-precision machining, semiconductor industry and biomechanics fields.

Electrochemical micromachining based on sinusoidal signals with variable resistance

ABSTRACT Reducing pulse duration is the sole effective strategy to improve the processing accuracy in ultra-short pulse electrochemical microfabrication. High cost and unsuitability in practical production also restrain its development. This study aims to propose a method based on sinusoidal signals with variable resistance. The bilayer capacitor cannot be fully charged to achieve a transient machining state. An equivalent circuit differential equation is established, and the resistance becomes an effective parameter to control the machining accuracy. The experimental result shows that the machining accuracy increases significantly with the increase in resistance. The approach is applied to machine microstructures and achieves sub-micron scale accuracy on a pure nickel sheet. The same superior machining accuracy can be obtained by machining microstructures on hard-to-cut superalloy plates.