Excitation Signal Research Articles

Research on Measurement Algorithm of Thermocouple Time Constant Under Multiple Incentive Experimental Conditions

ABSTRACTThe time constant is often an important indicator parameter to evaluate the response speed of thermocouples. However, in practical applications, the output signal suffers from interference and deformation due to the excitation signal not satisfying the desired step size, data transmission delay, and the effect of mechanical vibrations, which do not match the output response of the system of the same order. In addition, the measurement results are not reproducible due to the subjective influence of the manual measurement method. In this paper, we propose a method to compute the time constant. The output signal is modified by filtering and fitting to enable the automatic calculation of the time constant, and the parameters of the algorithm are discussed. We developed a thermocouple time constant measurement device using a water bath and laser excitation conditions, obtaining response signals from thermocouples with different wire diameters and laser powers. The results demonstrate the effectiveness of the proposed time constant calculation methods in accurately capturing the changing trend of thermocouples with different wire diameters and laser powers. These methods successfully meet the requirements for processing the dynamic response signals of thermocouples under various excitation conditions.

Automated interferometric stand for determination of amplitude-frequency characteristics of acoustic emitters

An automated interferometric stand (AIS) was created to determine the amplitude-frequency characteristics of acoustic emitters in the range from 0.5 to 200 kHz. The created AIS contains a unit for generating acoustic sinusoidal excitation pulse packets and a recording unit. The unit for generating acoustic pulse packets includes a generator of sinusoidal signals, a microprocessor unit for pulse packets generation and the AIS synchronization, a power amplifier of a sinusoidal signal to create a sufficient power of the acoustic emitter excitation signal. The recording unit includes a Michelson interferometer with a sound-conducting rod in one of the arms. One of the ends of the rod has a mirror surface. The other end is connected to the acoustic emitter through an acoustic contact. The length of the sound-conducting rod is 50 cm, which is enough to ensure measurements at the lower limit of the frequency range of the acoustic emitter radiation. The propagation time of the acoustic wave in the rod is of the order of 75 microseconds. As the end of the rod vibrates due to acoustic excitation, the initial path difference of the optical beams in the interferometer will change, causing a change in the intensity of the illumination produced by the interfering beams. These changes are recorded by photodiode in the other arm of the interferometer. After the photodiode signal is amplified in the amplifier, it is fed to the analog-to-digital converter, the output of which is transferred to the buffer memory, where the discretized values of the response signal amplitude during the time of the measuring pulse are accumulated. The control algorithm of the AIS is carried out with the help of developed software. The results of measuring the amplitude-frequency characteristics of mass-produced broadband acoustic emitters using AIS proved the satisfactory convergence of the obtained frequency responses with the passport data of these serial devices frequency responses. The amplitude-frequency characteristic of experimental sample of a piezoelectric acoustic emitter, made for research on the detection and identification of internal defects in laminated composite structures and "composite-concrete" adhesive joints, was obtained.

Impact resistance characteristics of pipeline system covered with W-shape elastic-porous metallic damper

As a novel elastic-porous damping material fabricated through entangled wire mesh, W-shape elastic-porous metallic damper (W-EPMD) is considered an ideal damping element for coated pipeline system due to the micro dry friction between metal wires, which induces energy dissipation. The complex interwoven cellular formations of metallic wire mesh pose challenges in characterizing its dynamic characteristics. In this work, the dynamic properties of the pipeline system covered with W-EPMD under various impact conditions, including the acceleration response and impact isolation coefficient, were investigated by numerical simulations and experimental analysis. Constitutive models used to characterize the hysteresis behavior of W-EPMD were introduced, comprising Yeoh and Bergström-Boyce models, and parameter identification were conducted through quasi-static experiments. The reliability of the established numerical model was confirmed through drop impact experiments. The results demonstrate that there is a maximum discrepancy of 9.1 % between the simulation predictions and experimental results of the stress-strain curve. The impact isolation coefficient of the pipeline system covered with W-EPMD exhibits a fluctuating trend with the rise of the pulse peak, while the maximum compression of W-EPMD steadily increases. During the pipeline impact process, the increased density of W-EPMD reduces the impact resistance of the pipeline system, while excessively low density leads to over-compression and structural damage to W-EPMD. Furthermore, the discrepancy of the acceleration response between experimental and numerical results under various excitation signals remain within 6 %, demonstrating that the hysteresis model effectively characterizes the impact resistance characteristics of the pipeline system covered the W-EPMD.

Lamb wave imaging via dual-frequency fusion for grating lobe effect compensation

In Lamb wave imaging based on a phased array, higher frequencies narrowband excitation pulses enable more precise damage detection and localization. However, due to the size constraints of individual transducer elements, the spacing between array elements may exceed half the wavelength of the excitation signal. This can lead to a grating lobe effect. To overcome this limitation, a Lamb wave imaging method via dual-frequency fusion for grating lobe effect compensation is proposed in this study. Analyses indicate that the grating lobe effect may introduce artifacts or distortions in the imaging results. This method utilizes two frequencies of narrowband excitation pulses for imaging and subsequently fuses the results. By doing so, the imaging artifacts caused by the grating lobes produced by high-frequency narrowband excitation pulses are effectively compensated. The proposed method is validated through simulations and experiments on an aluminum plate, showing superior accuracy, contrast, and imaging quality.

Rayleigh wave-based monitoring of mortar coating and concrete core cracking on prestressed concrete cylinder pipe under external pressure using piezoelectric lead zirconate titanate

Prestressed concrete cylinder pipe (PCCP) is a critical type of pressure pipe widely used in major water conveyance projects worldwide. As essential components of a PCCP, the mortar coating and concrete core are directly linked to its operational safety. This study employed piezoelectric lead zirconate titanate (PZT) devices as transducers to generate excitation vibrations and measure the resulting Rayleigh waves, thereby providing a means to detect cracking in and monitor the health of the mortar coating and concrete core of a prototype 1400 mm inner-diameter PCCP under external pressure. First, a theoretical analysis was conducted to define the propagation laws of Rayleigh waves. Next, a finite element analysis was undertaken to identify the tensile regions of the PCCP mortar coating and concrete core when under external pressure applied along the length of the PCCP and thereby establish the locations for the PZT devices. Experiments were subsequently conducted by incrementally increasing the external pressure load from 0 to 700 kN while monitoring the cracking in the mortar coating and concrete core using sinusoidal excitation signals with frequencies of 5, 10, and 20 kHz. The voltage amplitudes measured at each external pressure load were analysed, confirming the Rayleigh wave propagation laws and revealing that the change in the measured voltage amplitude curve aligned with the experimental observations, thereby validating the proposed measurement method. Finally, the relative percentage deviation of amplitude (RPDA) and relative percentage deviation of energy (RPDE) damage indices were established based on the voltage measurements to further evaluate the damage state of the mortar coating and concrete core. The RPDA measured at an excitation frequency of 20 kHz was best for detecting cracks in the PCCP mortar coating, whereas the RPDA and RPDE measured at excitation frequencies of 20 and 10 kHz, respectively, were best for monitoring concrete core cracking.

Enhancing the performance of a resonance-based sensor network for soft robots using binary excitation

Embedded, flexible, multi-sensor sensing networks have shown the potential to provide soft robots with reliable feedback while navigating unstructured environments. Time delay associated with extracting information from these sensing networks and the complexity of constructing them are significant obstacles to their development. This paper presents a novel enhancement to an existing class of embedded sensor network with the potential to overcome these challenges. In its original version, this sensor network extracts information from multiple reactive sensors on a two-wire electrical circuit simultaneously. This paper proposes to change the excitation signal applied to this sensor network to a binary signal. This change offers two key advantages: it provides the ability to employ small, inexpensive microcontrollers and results in a faster data extraction process. The potential of this enhanced system is demonstrated here with a proof of concept implementation. The self-inductance of all inductance-based sensors within this proof of concept sensor network can be measured at a rate of over 5000 times per second with an average measurement error of less than 2%.

Standardization of metal coil configuration in thermoacoustic imaging.

Existing TAI systems mostly use metal wires to calibrate their spatial resolution. However, research on the imaging mechanism of the metal wire and the setting of the wire parameters that can affect the system's spatial resolution is not sufficient in this context. In general, there is a lack of understanding of the factors affecting spatial resolution. A TAI system, consisting of parallel plate irradiation structures has been developed. Results show that the source of the thermoacoustic signals is the ohmic loss generated by the induced electromotive force. Moreover, the pulse width of the induced electromotive force signal is narrower than that of the system excitation signal, which holds the potential benefits for improving the spatial resolution of the TAI.

The rebar corrosion length evaluation technique based on nonlinear ultrasonic guided wave energy flow

In offshore reinforced concrete (RC) structures, phenomena of rebar corrosion are widespread, seriously threatening the durability of the structures. However, the issue of entire rebar corrosion process detection, especially for the evaluation of local corrosion states and the scope, is also challengeable. The paper aims at utilizing the nonlinear ultrasonic guided wave (UGW) energy flow to identify reinforcement corrosion level and length during the entire corrosion process in RC structures and establishing a corresponding corrosion evaluation algorithm. Therefore, a corroded rebar with the surrounding concrete cover is simplified into a cylindrical layered structural model. Meanwhile, piezoelectric transducers are used for the actuation and reception of UGWs, and a granular material contact (GMC) model is applied to illustrate the mechanism for generating surface-contact-induced nonlinear components in scattering waves. Then, the propagation behavior of the nonlinear UGWs is analyzed by regarding the corrosion layer as a secondary sound source changing the wave energy flow. A corrosion evaluation algorithm based on the GMC model is established and validated by both experiment and finite element (FE) analysis. The results show that for a harmonic UGW excitation signal, the periodic relationship between the second-order nonlinear coefficient of received signal and the corrosion length is found in which the period is associated with the difference (kd) of 2 times of fundamental frequency wave number (2 kω) and double frequency wave number (k2ω). Particularly, as kd trends to zero, a degraded linear relationship is found for establishing the corrosion length evaluation algorithm with the relatively high evaluation precision and convenient evaluation technique.

Multivariate Structural Vibration Coupling Response of the Self-Propelled Straw Pickup Baler Under Time-Varying Loads

The self-propelled straw pickup baler in agricultural work is responsible for collecting and compressing straw to facilitate transportation and storage, while reducing waste and environmental pollution. Like other agricultural equipment, the straw pickup baler is a complex mechanical system. During operation, its excitation characteristics under multi-source stimuli and the coupling characteristics of various components are not yet clear. This paper analyzed the excitation mechanics property of each component of the self-propelled straw pickup baler and established balance equations. Based on the balance equations, the coupling characteristics of the structures were studied. Through experiments collecting excitation signals from multiple devices under different operating conditions, the vibration excitation signals of each component were obtained. The experiments revealed that the excitation and coupling signals in the Z direction are particularly evident. Based on experiments, the effective Z-direction vibration signal value on the left front of the chassis exceeds 7 m·s2, while on the right front it increases from 1.995 m·s2 to 7.287 m·s2, indicating the most intense vibration direction. It was also found that, at the driver’s cab, the effective Z-direction vibration signal values at two response points, 11 and 12, both exceed 7 m·s2. The data indicate significant vibrations occur in both the longitudinal and vertical directions. Using the Signal Analyzer module in MATLAB for signal processing, it was found that the prominent filtered signals consist of combustion excitation harmonics and continuous low-frequency vibrations from the compression mechanism. The periodic reciprocating compression motion of the crank-slider mechanism causes sustained impacts on the frame, leading to periodic changes in the vibration amplitude of the chassis. Thus, the vibration reduction of the compression mechanism’s periodic motion is key to reducing the overall vibration of the machine.

Physical simulation study of fracturing monitoring of hot dry rock by borehole-surface electromagnetic method in frequency domain

Abstract The Chinese mainland has abundant hot-dry-rock (HDR) resources. However, large-scale application is significantly challenged by the fracturing and stimulation of HDR reservoirs, making monitoring HDR fracturing essential. The borehole-surface electromagnetic method, which involves borehole excitation and surface collection of electromagnetic signals, captures stronger secondary field signals, aiding in assessing and guiding the fracturing effects in HDR reservoirs. Despite its potential, research on this method for HDR fracturing monitoring is limited. To explore and validate the effectiveness and mechanism of the frequency-domain borehole-surface electromagnetic method for HDR fracturing monitoring, this study conducts physical simulation experiments. The experiments use water to simulate HDR caprock, a mixture of water and sand for the HDR layer, and a graphite-cement anomaly model for the HDR fractured zone. Results indicate significant differences in electric field response amplitudes before fracturing, during fracturing, and after fracturing. When excited below and at the center of the anomaly model, the Ey response amplitude decreases with lower model resistivity, and when excited at the center, the Ey response amplitude similarly decreases with reduced resistivity. These findings demonstrate that the borehole-surface electromagnetic method effectively reflects changes in resistivity within the fracturing anomaly model, making it a suitable electromagnetic exploration method for monitoring HDR fracturing.

Multifrequency electrical impedance tomography system based on undersampling combined with a fast digital demodulation algorithm.

Multifrequency electrical impedance tomography (MFEIT) has shown great application prospects in the field of biomedical imaging. To realize high-precision multifrequency electrical impedance information acquisition, a high-precision MFEIT system with undersampling combined with a fast digital demodulation algorithm is proposed. The system is integrated with 16 electrodes, and semi-parallel acquisition is used. In addition, a novel multifrequency digital demodulation algorithm is applied to enhance the accuracy of multifrequency excitation signal demodulation and achieve rapid demodulation. This improvement is achieved by analyzing the process of the multifrequency digital demodulation algorithm and combining undersampling with a fast digital demodulation technique. To evaluate the proposed method, a systematic comparative experiment is conducted. The experimental results demonstrate that the demodulation error using the undersampling method is less than 0.7% within the frequency range of 5-500kHz. In addition, the system achieves a maximum signal-to-noise ratio of 62.92 dB, an average blur radius of 0.953, and an average position error percentage of 9.3%. The results indicate that the MFEIT system constructed based on the above research has good performance and a high signal-to-noise ratio.

A multimodal rotational acoustic manipulation device for hydrophilic/hydrophobic floating and submerged particles

Rotational acoustic manipulation technology offers precise control of particle motion, making it advantageous for applications in microfluidics, biomedicine, materials research, and so on. Current advanced techniques that use acoustic waves to rotate particles include microstructure vibration, microbubble oscillation, and acoustic holography. Although these methods have achieved some success in rotational acoustic manipulation, they face challenges such as limited types of particles, complex device fabrication, and single-mode manipulation. To address these issues, this study proposes a novel rotational acoustic manipulation device based on traveling wave acoustic fields. The traveling wave acoustic field is achieved by planning the vibration modes of the vibrational source. In this study, a ring-shaped piezoelectric ceramic with four-quadrant dual polarization is designed to excite two orthogonal B11 bending vibration modes of the vibrator. By adjusting the phase difference of the excitation signals, these two B11 bending vibration modes can be coupled into either clockwise or counterclockwise traveling wave vibration modes, thereby establishing unidirectional rotating traveling waves in the water within the PDMS ring. The PDMS ring features an open structure, meeting the requirements for manipulating both floating and submerged particles. The performance of the proposed acoustic manipulation device is validated and analyzed through experiments with hollow glass particles, hollow polystyrene particles, and solid polystyrene particles. The results demonstrate that the proposed acoustic manipulation device can achieve precise fixed-point self-rotation and regional revolution manipulation of particles, regardless of their floating, submerged, hydrophilic, or hydrophobic properties. This indicates the high universality and robustness of the device, making it applicable for the manipulation of various types of particles. Overall, this study introduces a novel acoustic manipulation method for particle rotation, providing strong support for the development and application of acoustic manipulation devices in diverse fields.

Multimodal modeling and identification study of a quadrotor robot

Abstract The flight control system of a flying robot plays a crucial role. Therefore, it is imperative to establish various flight mode control models. Traditional modeling methods face challenges in meeting the demands of rapid research and development due to the emergence of diverse aircraft shapes and load forms. To address these issues, this study focuses on multi-conditions modeling and system identification. Based on flight dynamics theory, a comprehensive quadrotor robot dynamics model along with its state space model was established. Flight tests were designed for system identification under different flight modes. The data obtained from the flight test was preprocessed using an extended Kalman filter algorithm based on flight path reconstruction technology to reduce constant deviation from airborne sensors. Frequency response identification technology was employed to identify control models for hovering mode and forward flight at 10m/s mode in the quadrotor robot. Model structures were determined based on precision index evaluation criteria. Time-domain validation method was utilized to simulate fitting error RMS for each channel model under multiple conditions using different signal excitations derived from datasets collected during experiments. The results confirmed that the proposed aircraft system identification method is effective and feasible.

Ударное воздействие сверхкороткого импульса света на прецессию намагниченности в магнитоупругой системе

The task about interaction of super-short light pulse on magnetoelastic system which has precession motion of magnetization is investigated. As a main mechanism it is investigated the decreasing of magnetization with power light action on spin system. It is investigated the development of magnetization precession by the action of light pulse. It is found that during the pulse action the amplitude vibrations is decreased and its frequency is increased. It is investigated the precession development in different meanings of light power. It is established the multi-regime character of magnetization vibrations by small pulse duration which is the same order as signal excitation period. It is established three regimes: regime №1 – stabile vibrations, regime №2 – the destroy of stabilization, regime №3 – shock excitation. It is established that the main distinguishing of regime №3 from first two regimes is the sharp jump increasing of amplitude as magnetic so the elastic vibrations which take pulse as a result of pulse action. It is found that as a result of high power long duration pulse it is arising the regime of in-flatness magnetic component stabilization. It is found that the main role in formation of this regime plays the magnetoelastic interaction.

Analysis of the Seismic Vulnerability of a Masonry Pagoda Based on Increasing Dynamic Analysis

ABSTRACTFor the seismic vulnerability analysis method of masonry pagodas, the dynamic characteristic of the Bayun Pagoda in China was conducted by using environmental excitation technology. A numerical model of the masonry pagoda was established with the finite element software Abaqus. Ten seismic waves were selected as excitation signals to conduct incremental dynamic analysis (IDA) on the pagoda. The Sa(T1,5%) served as the seismic intensity indicator, whereas the damage factor (d) and relative stress () were employed as damage indicators for seismic vulnerability analysis of the pagoda. The failure probability of the structure reaching the limit state under different seismic intensities was determined. The results indicate that, comparing the IDA curves and seismic vulnerability curves under two different damage indicators, the Sa(T1,5%) range required for the IDA curves under the damage factor (d) is smaller than the relative stress (), with lower dispersion. Additionally, the failure probability of the pagoda reaching different limit states is higher under the damage factor (d). Considering the existing damage status of the masonry pagoda, the damage factor (d) is more reasonable as the damage indicator.

Design and Signal-Decoding Test Verification of Dual-Channel Round Inductosyn Decoding Circuit

During the in-orbit operation of spacecraft, permanent magnet synchronous motors are commonly used as power sources in the drive mechanisms of solar panel arrays and the high-precision servo control systems based on satellites. Apart from the performance of the motors themselves and the software control algorithms, the accuracy of the entire control system is also influenced by angle sensors used to detect the rotor position of the motors. As a high-precision angular measuring instrument, the inductosyn possesses excellent environmental adaptability and long service life. Effectively utilizing the inductosyn can greatly enhance the performance of servo control systems. To address the complexity of the decoding process for dual-channel round inductosyn-to-digital converters, this paper proposes a design of the decoding circuit for dual-channel round inductosyn based on the parallel-synchronization decoding method of two AD2S1210 Resolver-to-Digital Converter (RDC) decoding chips. The decoding circuit amplifies the excitation signal outputted by the AD2S1210 for driving the round inductosyn, and processes the sine and cosine induction signals outputted by the round inductosyn through filtering, amplification, and other methods; by using analog circuitry, the output signals of the dual-channel round inductosyn are processed to meet the input requirements of the AD2S1210. Finally, through both the Multisim (circuit simulation software Version 14.1) simulation and physical experiments, it was verified that the decoding circuit designed in this paper could process the input/output signals of the dual-channel round inductosyn and AD2S1210, and successfully decoded the analog induction signal of the round inductosyn. This greatly simplifies the signal decoding process for the dual-channel round inductosyn.

Fast impedance measurement method for large capacity batteries using chirp and filtered pseudo-random binary sequence

Fast impedance measurement with well-constructed excitation signals is crucial for battery internal states analysis and faults diagnosis. The pseudo-random binary sequence (PRBS) is a promising time-efficient excitation signal, but it lacks power content in the low-frequency range and is susceptible to high-frequency harmonics beyond the measurement limits, especially for square large-capacity batteries. Motivated by this, this paper proposes a novel parallel-connected signal derived from filtered PRBS and chirp sequence to boost low-frequency components while mitigating high-frequency effects. Meanwhile, to enhance accuracy in measuring square large-capacity batteries with low impedance, the paper introduces a differential amplification circuit to improve voltage response robustness against noise. Experimental results confirm the effectiveness of this method, achieving precise impedance measurements across the 0.1 Hz–1000 Hz range in just 10.24 s. With different states of charges, temperatures, and battery types, errors of the measurement are below 3.67 %.

Research on fractional-order memory system signals based on Loop-By-Loop Progressive Iterative Method

This article abandons the traditional Laplace transform and proposes a new method for studying fractional-order circuits, which is the Loop-By-Loop Progressive Iterative Method(LPIM). Firstly, in order to demonstrate the correctness of LPIM, the fractance circuit, which is a relatively mature and simple form in fractional-order circuits, was chosen as the research object. The output signals of fractance circuit were studied for the first time using Laplace transform and LPIM, respectively. The results showed that the conclusions obtained by LPIM were completely consistent with those obtained by Laplace transform method and existing theories, thus verifying the correctness of LPIM. Then, a brand new Fractional-Order Memory Systems (FMS) model is constructed, and based on this model, LPIM is used for the first time to simulate the output signal of Flux-Controlled Fractional-Order Memory Systems (FFMS) that has not been studied so far. The results show that when a sine signal is used as the excitation signal, the output signal of the FFMS intersects at two points, and the output signal is modulated by the frequency of the excitation signal. Finally, combining existing theories, predict the output commonalities of FMS.

Design and optimization of large-range absolute linear displacement sensors based on splicing technology

This paper proposes a high-resolution absolute time-grating displacement sensor, which can splice multiple ruler segments to expand the measurement range. The single-segment range of a ruler using a vernier structure for absolute measurement is 400 mm, through which the method of remodulation (i.e., the output signal of the first-level unit) is used as the excitation signal of the second- and third-level units to increase the measurement period and realize the passive design of the mover. To make a smooth transition of the signal near the joint, we set two independent sets of sensing structures on the mover. We obtain the state judgment coding signal and displacement value through the traveling wave signal received on the ruler and the absolute position judgment is realized by combining the position state and displacement value. The use results indicate that the measurement range of the sensor increases to 1200 mm after splicing, and the measurement accuracy reaches ± 5 μm.

A Universal Plug-and-Play Approach to In Situ Multinuclear Magnetic Resonance Analysis of Electrochemical Phenomena in Commercial Battery Cells.

Advancing electrochemical energy storage devices relies on versatile analytical tools capable of revealing the molecular mechanisms behind the function and degradation of battery materials in situ. The nuclear magnetic resonance phenomenon plays a pivotal role in fundamental studies of energy materials and devices because of its exceptional sensitivity to local environments and the dynamics of many electrochemically relevant elements. The jelly roll architecture is one of the most energy-dense and, therefore, most popular concepts implemented in pouch, prismatic, and cylindrical Li- and Na-ion cells. Such widely commercialized designs, however, represent a significant obstacle for a range of powerful in situ magnetic resonance-based methodologies due to negligible radio frequency electromagnetic field penetration through conductive metal casings and current collectors. In this work, we introduce an experimental setup that enables direct RF wave transmission through the cell terminals and current collectors, and provides efficient excitation and detection of NMR signals. An RF adapter designed as a plug-and-play device effectively turns the battery cell into an NMR probe that can be tuned to a broad range of Larmor frequencies. Due to its exceptional sensitivity, versatility, and multinuclear capability, the proposed methodology is suitable for fundamental research and industrial high-throughput screening applications. In situ NMR lineshapes provide a direct quantitative description of the chemical environments of electrochemically active elements and enable new metrics for the accurate assessment of state-of-charge (SoC) and state-of-health (SoH). Specifically, in commercial pouch cells based on lithium cobalt oxide, lithium nickel manganese cobalt oxide, and sodium nickel iron manganese oxide chemistries, 7Li and 23Na NMR data unambiguously show electrochemical transformations between intercalated and metallic forms of charge carrier ions, and reveal anisotropic magnetic properties of the electrode coating.