Journal articles: 'Amplitude-frequency characteristic'

1

Klaerner, Matthias, Mario Wuehrl, Lothar Kroll, and Steffen Marburg. "Characteristic amplitude-frequency functions of the radiated sound power." Journal of the Acoustical Society of America 141, no. 5 (May 2017): 4034. http://dx.doi.org/10.1121/1.4989301.

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Liu, Hai Jiang, and Hong Yan Wang. "Development of the Amplitude-Frequency Characteristic Tester Based on SCM Control." Advanced Materials Research 706-708 (June 2013): 776–80. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.776.

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In this paper, the development of the amplitude-frequency characteristic tester based on SCM control has been introduced. The digital frequency synthesizer has been adopted to generate the automatic sweep frequency sine signals so as to provide the reliable sources for the frequency characteristic tester. The amplitude and the frequency characteristics of the active network and the passive network can be obtained through changing the output signals of circuit measuring network by digital analogy as well as the operation program of the microcontroller under the input signals with different frequencies. In this paper, the working principles of tester, the software and hardware design for the frequency synthesizer signals, the hardware and software design of the data collection channels and the applications of LCD technology have been specially discussed.

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Yu, Liang Jun, Li Hua Sun, and Cui Cui Huang. "Design of Comprehensive Test Instrument Based on FPGA and Cortex-M0." Applied Mechanics and Materials 312 (February 2013): 583–87. http://dx.doi.org/10.4028/www.scientific.net/amm.312.583.

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The design consists of three modules: the voltage amplitude measurement module, the level oscillator module and the amplitude-frequency characteristic test module. The voltage amplitude measurement module uses AD817 to consist three-stage amplifier. The magnification of each level can be adjusted for 1 times/10 times. At the same time, the author uses the Cortex-M0 for controlling the relay switch to achieve automatic range conversion. The principle of DDS is adopted in the level oscillator module. FPGA is used for realizing the phase accumulator, the phase modulator, the sine ROM look-up table. Digital signal is finally outputted by high-speed analog-to-digital conversion chip DAC900. Then, by controlling the 6-channel relay switch to make the magnification in the amplifying circuit,which can be adjusted step-by-step from-30dB to 20dB. Through outputting sine wave whose amplitude is fixed, but frequency is variable to the network under test, amplitude-frequency characteristic test module measures the relation betthe authoren the amplitude change of the output signal and the signal frequency to obtain the amplitude-frequency characteristics of the network under test..

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Паровик, Р. И. "Анализ добротности вынужденных колебаний дробного линейного осциллятора." Журнал технической физики 90, no. 7 (2020): 1059. http://dx.doi.org/10.21883/jtf.2020.07.49436.233-19.

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Using the harmonic balance method, analytical formulas are obtained for calculating the amplitude-frequency and phase-frequency characteristics, as well as the quality factor of the forced oscillations of a linear fractional oscillator. It was established that the characteristics under study depend on the dissipative properties of the medium - memory effects, which are described by derivatives of fractional orders. It is shown that fractional orders affect the attenuation of the oscillatory process and are associated with its quality factor. The calculated curves of the characteristics of the forced oscillations of a linear linear fractional oscillator showed that fractional orders can be considered as control parameters of the oscillatory process in a dissipative medium. Key words: quality factor, amplitude-frequency characteristic, phase-frequency characteristic, fractional derivatives, memory.

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Abramov, Y., V. Kryvtsova, and A. Mikhailyuk. "JUSTIFICATION OF THE METHOD OF DETERMINATION OF THE CONSTANT TIME OF THE GAS GENERATOR OF THE SYSTEM OF STORAGE AND SUPPLY OF HYDROGEN." Municipal economy of cities 3, no. 163 (June 29, 2021): 216–20. http://dx.doi.org/10.33042/2522-1809-2021-3-163-216-220.

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The method of determining the dynamic parameter - the time constant of the gas generator of the storage and supply of hydrogen on the basis of the hydro-reactive composition is substantiated. The method is based on the use of the amplitude-frequency characteristics of the gas generator of the storage and supply system of hydrogen. The method involves the implementation of three stages. At the first stage, the mathematical dependence of the gas generator time constant on its static parameter and amplitude-frequency characteristic at a fixed frequency is obtained. In the second stage, the choice of this fixed frequency is justified. This dependence includes the value of the amplitude-frequency characteristic of the gas generator of the storage and supply of hydrogen at a fixed frequency, the static parameter of such a gas generator – its transmission coefficient, and the value of the fixed frequency. In the second stage, the choice of this fixed frequency is justified. This choice is made provided that the minimum error in determining the time constant of the gas generator. To determine the static parameter of the gas generator and the value of its amplitude-frequency characteristic at a fixed frequency, an array of data is used, which is formed by measuring the values of the transient function of the gas generator through equal moments of time. These time intervals are chosen according to the Kotelnikov-Nyquist-Shannon theorem. The amplitude-frequency characteristic of the gas generator of the hydrogen storage and supply system is determined numerically. According to the research results, an iterative procedure for determining the time constant of the gas generator of the hydrogen storage and supply system is given. Recommendations for using this procedure are given. The choice of the time constant of the gas generator of the hydrogen storage and supply system is made using the tolerance criterion.

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Xu, Lu, Hongsheng Li, Jia Liu, Yunfang Ni, and Libin Huang. "Research on Nonlinear Dynamics of Drive Mode inZ-Axis Silicon Microgyroscope." Journal of Sensors 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/801618.

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A novel drive method is proposed to increase the vibration amplitude of drive mode of silicon vibratory gyroscopes based on the nonlinear dynamics research made in this paper. A nonlinear dynamic equation, considering the nonlinear mechanical-elastic and electrostatic force, was firstly deduced according to the simplified structure schematic of drive mode. Then, experiments were made to characterize the nonlinear amplitude-frequency response characteristic as well as its dependence on drive voltage. Besides, by solving the nondimensional nonlinear dynamics using Matlab and Simulink, the influence of initial status of drive mode, that is, the displacement and the velocity, on the stable vibration amplitude was presented. The amplitude-frequency characteristic was also analyzed by simulation. The result of simulation shows good agreement with that of experiments. When nonlinearity is present in the amplitude-frequency characteristic, there is a wide flat region with larger amplitude than the peak amplitude obtained in the linear characteristic. Finally, a novel drive method was presented to excite the nonlinear vibration of large amplitude in the downwards-sweeping characteristic curve. It is numerically proved that this merit can be utilized to enlarge the drive mode’s vibration amplitude so as to enhance silicon gyroscopes’ performance.

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Parovik, Roman. "Frequency characteristics of the fractional oscillator Van der Pol." E3S Web of Conferences 127 (2019): 02010. http://dx.doi.org/10.1051/e3sconf/201912702010.

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Into this paper, the amplitude-frequency and phase-frequency characteristics of the Van der Polar fractional oscillator are studied in order to establish their relationship with the orders of fractional derivatives included in the model equation. Using the harmonic balance method, analytical formulas were obtained for the amplitude-frequency, phase-frequency characteristics, as well as the quality factor – the energy characteristic of the oscillatory system. It was shown that the quality factor depends on the orders of fractional derivatives, and change in their values can lead to both an increase and a decrease in the quality factor.

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Li, Li Ping. "Experiment Analysis about Mechanical Properties of Rubber Bushing for Suspension Telescopic Shock Absorber." Applied Mechanics and Materials 670-671 (October 2014): 1008–11. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.1008.

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The experiments of static and dynamic characteristics of rubber bushing for rear suspension telescopic shock absorber were carried out at four directions such as axial, radial, torsion and yaw, by MTS831 and SAGINOMIYA test system. The tests prove that: rubber bushing has great damping, and rubber bushing has obvious nonlinear characteristic; the dynamic stiffness under low frequency and large amplitude excitation is smaller, while the dynamic stiffness under high frequency and small amplitude excitation is greater; at the same amplitude, the dynamic stiffness increases with the increasing excitation frequency. The test results can provide support for the optimization design of rubber bushing.

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Xu, Jinli, Jiwei Zhu, and Feifan Xia. "Modeling and Analysis of Amplitude-Frequency Characteristics of Torsional Vibration for Automotive Powertrain." Shock and Vibration 2020 (August 29, 2020): 1–17. http://dx.doi.org/10.1155/2020/6403413.

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In the present paper, the amplitude-frequency characteristics of torsional vibration are discussed theoretically and experimentally for automotive powertrain. A bending-torsional-lateral-rocking coupled dynamic model with time-dependent mesh stiffness, backlash, transmission error etc. is proposed by the lumped-mass method to analysis the amplitude-frequency characteristic of torsional vibration for practical purposes, and equations of motive are derived. The Runge–Kutta method is employed to conduct a sweep frequency response analysis numerically. Furthermore, a torsional experiment is performed and validates the feasibility of the theoretical model. As a result, some torsional characteristics of automotive powertrain are obtained. The first three-order nature torsional frequencies are predicted. Torsional behaviors only affect the vibration characteristics of a complete vehicle at low-speed condition and will be reinforced expectedly while increasing torque fluctuation. Gear mesh excitations have little effects on torsional responses for such components located before mesh point but a lot for ones behind it. In particular, it is noted that the torsional system has a stiffness-softening characteristic with respect to torque fluctuation.

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Ma, Liang, Jun Wang, and Guichang Zhang. "The Dynamic Characteristic of a Faulted Rotor System with Multi-Objective Optimization Designed SFD." Applied Sciences 9, no. 17 (September 3, 2019): 3628. http://dx.doi.org/10.3390/app9173628.

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As an important part of the turbomachinery, the rotor–bearing system has been upgraded to provide a high rotating speed in order to meet the demand of high power production. With increasing demand for stability, the squeeze film damper (SFD) has been widely used in industrial machinery because it can reduce the vibration amplitude and suppress the external force. Usually, it shows inadaptability under the different working conditions where the SFD parameters didn’t change appropriately. Therefore, the reasonable choice of operational parameters of SFD is the key solution that can provide viscous damping effectively and restrain the nonlinear vibration generated by faults. In this paper, the mathematical model of a rotor-ball bearing-SFD system considering the misalignment fault and misalignment-rubbing coupling fault is built first. Then the dynamic characteristics under typical working conditions (ω = 1000 rad/s) of the faulted rotor are discussed. The vibration attenuation effects of the SFD parameters selected by using the multi-objective optimization method on the dynamic responses are analyzed. The results show that when the rotor system operates under different states, the value and the sensitivity of optimization parameters are altered. With no fault, the amplitude of fundamental frequency decrease 23%. With the misalignment fault, the amplitude of the fundamental frequency decreases by 43.4%, the amplitude of 2× fundamental frequency decreases by 27.5%, and the amplitude of 3× fundamental frequency decreases by 66.7%. With the misalignment-rubbing coupling fault, the amplitude of fundamental frequency reduces by 7.4%, the amplitude of 2× fundamental frequency drops by 51.5%, and the amplitude of 3× fundamental frequency drops by 16.8%. Overall, the feasibility of the optimization method of the variable-structured SFD operational parameters for the faulted rotor system is verified. These parametric analyses are very helpful in the development of a high-speed rotor system and provide a theoretical reference for the vibration control and optimal design of rotating machinery.

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Chu, Hai Rong, Bo Liu, and Yue Zhang. "Three-Loop Autopilot Frequency Characteristic Measurement." Applied Mechanics and Materials 494-495 (February 2014): 1332–34. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.1332.

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In order to measurement frequency characteristic of the missile three loop autopilot, three loop autopilot system model of the missile pitch channel was established. Then the autopilot system open-loop model was analyzed , and also open-loop frequency calculation formula was deduced. On the basis of the autopilot system model, half physical frequency characteristic measurement system was built, and the experimental data were processed by using correlation analysis method. Experimental results shows that when the time delay of measurement system was compensated, three loops autopilot actual cut-off frequency was 47.5rad/s, phase margin was 93°, amplitude margin was infinte, compared with the theoretical value, errors was less than 5%. The correctness of three loops autopilot frequency characteristic measurement method was verified.

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Xu, Qian, Zhong-Qi Wang, Wen-Gong Han, and Cheng-Long Yu. "Seismic wavefield model excited by a finite long cylindrical charge." GEOPHYSICS 87, no. 3 (February 25, 2022): P15—P28. http://dx.doi.org/10.1190/geo2020-0260.1.

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The amplitude-frequency characteristic of a seismic wave excited by explosion sources directly affects the accuracy of seismic exploration. To reveal the effect law related to a cylindrical charge, this research proposes a seismic wavefield model excited by a long cylindrical charge. According to the characteristics of the blasting cavity generated by a finite-length cylindrical charge, the seismic wavefield characteristics of a cylindrical charge excitation are obtained by superposing the seismic wavefield excited by a series of spherical charges. Numerical simulation results show that the calculation error of the blasting cavity characteristics of the theoretical model is within 10%. The comparison with field experimental results shows that the error of the model is within 9.4%. The velocity field of the excited seismic wave is almost the same as that of the spherical charge when the explosion distance to the cylindrical charge with finite length is 16–21 times longer than the charge length, but the frequency of the seismic wave is 30% higher than for a spherical charge. Moreover, the explosive velocity has a certain influence on the amplitude-frequency characteristic of the seismic wave excited by the cylindrical charge. The established theoretical model can accurately describe the amplitude-frequency characteristics of the seismic wavefield excited by a cylindrical charge with finite length.

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Zeng, Xiang Kun. "Experimental Analysis of Dynamic Characteristic for Automatic Tensioner." Advanced Materials Research 915-916 (April 2014): 49–52. http://dx.doi.org/10.4028/www.scientific.net/amr.915-916.49.

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Experimental method and parameters to investigate the dynamic performances of an automatic tensioner are discussed. Parameters to evaluate the dynamic performances of a tensioner include dynamic stiffness, loss angle and equivalent viscous coefficient. Dynamic stiffness and loss angle can be measured directly, and the equivalent viscous coefficient can be calculated by torque-angular displacement loop which identified with the parameters including dynamic stiffness, loss angle, pre-load torque, pre-load angular displacement, excitation amplitude and excitation frequency. In this paper, the influences of excitation amplitude, excitation frequency and pre-load torque on the dynamic characteristics of tensioner are measured and investigated.

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Chaari, Fakher, Walter Bartelmus, Radoslaw Zimroz, Tahar Fakhfakh, and Mohamed Haddar. "Gearbox Vibration Signal Amplitude and Frequency Modulation." Shock and Vibration 19, no. 4 (2012): 635–52. http://dx.doi.org/10.1155/2012/839420.

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Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity) and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case.The experimental validation presented at the end of the paper confirms the obtained results. Such results offer useful information when diagnosing gear transmissions by avoiding confusing conclusions from vibration signals.

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Liu and Zhong. "Research on an Electromagnetic Interference Test Method Based on Fast Fourier Transform and Dot Frequency Scanning for New Energy Vehicles under Dynamic Conditions." Symmetry 11, no. 9 (September 1, 2019): 1092. http://dx.doi.org/10.3390/sym11091092.

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In recent years, electromagnetic interference (EMI) of new energy vehicles, including difference mode symmetric interference and common mode asymmetry interference, has attracted the attention of many scholars. So far, EMI tests for new energy vehicles under steady conditions cannot reflect the actual EMI of the running vehicle. The results of EMI test methods based on fast Fourier transform (FFT) under dynamic conditions have worse frequency resolutions, and frequency/amplitude accuracy has low precision. Therefore, this paper proposes an EMI test method based on FFT and dot frequency scanning (DFS) for new energy vehicles under dynamic conditions. The identification method for accelerating, sliding, and braking conditions is studied. A comprehensive EMI key evaluation index system for new energy vehicles is built, including characteristic points with maximum amplitude, area, ratio, and density coefficients for high-amplitude characteristic points. Among them, the maximum amplitude is an index to evaluate extreme values. The ratio of high-amplitude characteristic points is a comprehensive index to evaluate the overall region. The density coefficient is an index to evaluate the local region. Finally, this method is applied to three vehicles. With the same instruments, by reducing the FFT frequency span, the frequency resolution and frequency accuracy increase. The results indicate that the EMI of new energy vehicles can be tested under dynamic conditions with high accuracy according to the operable evaluation indexes.

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Zhao, Yan Ping, Zi Long Zhao, and Guo Yun Lu. "Analysis of Steel Rope Shock Absorber Amplitude Frequency Characteristics under the Basic Excitation." Applied Mechanics and Materials 312 (February 2013): 287–91. http://dx.doi.org/10.4028/www.scientific.net/amm.312.287.

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In this paper, the differential equations of the steel rope shock absorber are established under the basic excitation, using the Fourier series expansion method and the Harmonic balance method, the corresponding frequency response equations are derived, then their numerical solutions is got, and the influence of the mass, damping, stiffness, and hysteretic force on the frequency response characteristic is analyzed under the basic excitation. It can be drawn by analyzing and comparing. Under the basic excitation, with the basic simplified mass increasing, the natural frequency will decrease, while the resonance amplitude will increase. With the steel rope damping, stiffness and the foundation damping increasing, the natural frequency will not change significantly, while the resonance amplitude will decrease. With the foundation stiffness increasing, the natural frequency and the resonance amplitude will increase significantly. The equipment mass and steel rope hysteretic force have no significant effect on the frequency response characteristics.

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Abramov, Y., V. Kryvtsova, and A. Mikhailyuk. "ALGORITHM FOR DETERMINATION OF RELIABILITY INDICATOR OF GAS GENERATOR OF HYDROGEN STORAGE AND SUPPLY SYSTEM." Municipal economy of cities 4, no. 164 (October 1, 2021): 153–57. http://dx.doi.org/10.33042/2522-1809-2021-4-164-153-157.

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An algorithm for determining one of the indicators of reliability of the main element of the hydrogen storage and supply system – a gas generator has been developed. Such an algorithm is an integral part of the general algorithm to ensure the required level of fire safety of hydrogen storage and supply systems. The algorithm involves the implementation of several stages. At the first stage, using the expression for the amplitude-frequency characteristic of the gas generator, the functional dependences for its time constants are obtained. These functional dependencies include the values of the transmission coefficient and amplitude-frequency characteristics, which are determined at three a priori set values of frequency. In the second stage, the amplitude-frequency characteristic of the gas generator is determined. For this purpose, an array of data is used, which characterizes the reaction of the gas generator to the test effect in the form of an abrupt change in the area of its outlet. The amplitude-frequency characteristic of the gas generator is determined numerically, and its parameters are the increase in the pressure in the cavity of the gas generator and the time interval at which this increase is determined. The Kotelnikov-Nyquist-Shannon theorem is used to determine this time interval. At the third stage, the probability of the values of the time constants of the gas generator outside the tolerance zone is determined. For this purpose, models of gas generator time constants and their metrological characteristics are used. In the fourth stage, the probability of failure of the gas generator is determined, for which the information of the previous stage is used. At the last stage, the algorithm for determining the probability of failure of the gas generator of the storage and supply system of hydrogen, which is given in verbal form.

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Xu, Hui, Zeng Tian Yan, Yang Wang, and Song Wei Gao. "Transmission Design of the Ultrasonic Flow Measurement Based on the Correlation Method." Advanced Materials Research 503-504 (April 2012): 1441–44. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.1441.

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In design of ultrasonic flow measurement, the reproducibility of constant amplitude periodic signal will lead to a not unique time difference based on the correlation method. The aim of this paper is to design a set of amplitude modulation transmitting signal to solve the multiple values calculation of the time difference. The frequency characteristics of ultrasonic probe and the amplitude frequency characteristic of different duty cycle square wave are researched and tested. We cleverly combine the logic device FPGA with the property of the ultrasonic probe to achieve the amplitude modulation waveform in the circuit design. The experimental results show that FET switch controlled by the logic device FPGA can transmit amplitude modulation signal. The measured error of time difference after correlation is not more than 1.62s.

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Li, Yajie, Zhiqiang Wu, Qixun Lan, Yujie Cai, Huafeng Xu, and Yongtao Sun. "The modulation of response caused by the fractional derivative in the Duffing system under super-harmonic resonance." Thermal Science 25, no. 3 Part B (2021): 2357–67. http://dx.doi.org/10.2298/tsci191201126l.

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The dynamic characteristics of the 3:1 super-harmonic resonance response of the Duffing oscillator with the fractional derivative are studied. Firstly, the approximate solution of the amplitude-frequency response of the system is obtained by using the periodic characteristic of the response. Secondly, a set of critical parameters for the qualitative change of amplitude-frequency response of the system is derived according to the singularity theory and the two types of the responses are obtained. Finally, the components of the 1X and 3X frequencies of the system?s time history are extracted by the spectrum analysis, and then the correctness of the theoretical analysis is verified by comparing them with the approximate solution. It is found that the amplitude-frequency responses of the system can be changed essentially by changing the order and coefficient of the fractional derivative. The method used in this paper can be used to design a fractional order controller for adjusting the amplitude-frequency response of the fractional dynamical system.

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Yong, Yang, Shuai Zhang, and Yan Huai Qu. "HHT Based Analysis on Experiments of Rotor System with Rub-Impact." Advanced Engineering Forum 2-3 (December 2011): 111–16. http://dx.doi.org/10.4028/www.scientific.net/aef.2-3.111.

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Based on the demand of engineering, the motion characteristics and time-frequency properties of rotor system with rub-impact at fixed limiter are studied by experiment. Three typical cases at different rotating speeds are chosen from the experiment. On the basis of traditional amplitude spectrum and shaft center orbit methods, Hilbert-Huang transformation is applied to the fault signals analysis. Fault features are characterized completely and accurately by Hilbert spectrum. It is show that the vibration of the system is with typical characteristic of periodic motions and corresponding time-frequency (instantaneous frequency) -amplitude /energy representations in the rotor system with rub-impact at fixed limiter.

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Wan, Di Qing, Bo Lin He, Jin Cheng Wang, and Gen Cang Yang. "Strain Amplitude Dependence of Damping Capacity in High Damping Mg-Based Alloys Continuously Extending to Microplastic Strain." Advanced Materials Research 97-101 (March 2010): 937–40. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.937.

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An investigation on low frequency strain amplitude dependence damping characteristic of as-cast high damping Mg-based alloys continuously extending to microplastic strain was carried out. Two-stage damping behavior via strain amplitude was particularly reported. The first is the strain amplitude strongly dependent part due to breakaway loss and the second is the strain amplitude weakly dependent part due to microplastic deformation loss, which is also frequency dependent. The damping mechanism is discussed in detail.

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Власов, В. С., В. Г. Шавров, and В. И. Щеглов. "Нелинейное расщепление линии магнитоупругого резонанса в сильно возбужденном феррите." Журнал технической физики 92, no. 1 (2022): 62. http://dx.doi.org/10.21883/jtf.2022.01.51853.167-21.

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The nonlinear splitting of magnetoelastic resonance line in powerfully excited ferrite is investigated. It is shown that the amplitude of splited resonance has the same order of value that the amplitude of basis resonance and its frequency is determined by the upper boundary of nonlinear amplitude-frequency characteristic of magnetic system. It is found the threshold character of splitting additional resonance from general. It is determined the possibility of operation of splited elastic resonance frequency by changing of exited magnetic field value which has practical importance.

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Fernanda, E., A. Bilqis, L. Julio, K. Nursal, Y. H. Christ, T. Adiansyah, S. K. Suhardja, and M. Ramdhan. "Early Result for Microtremor Characteristic Observation in Merapi and Merbabu." IOP Conference Series: Earth and Environmental Science 873, no. 1 (October 1, 2021): 012077. http://dx.doi.org/10.1088/1755-1315/873/1/012077.

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Abstract The arc magmatism and volcanic activity in Java are dominated by the subducting plate of Indo-Australian into the Eurasian plate. Merapi volcano is located in Central Java and known as one of the most active volcanoes in the world. Several studies have tried to estimate the magma reservoir zone in Mt. Merapi and suggested multiple layers of reservoirs with the shallow one at 1-2 km and a deeper at 6 -9 km or 15 km. The Low-Frequency Passive Seismic is one method to analyze the frequency spectrum below the recording station. Previous related studies show a promising a relation between hydrocarbon reservoir and higher amplitude at vertical component at a frequency between 0.1 – 6 Hz. An observation at the volcano sites have also been reported to display a different spectrum amplitude at the vertical component. This study exploited the same method in LFPS to analyze the frequency spectrum at Mt. Merapi and Mt. Merbabu. We use seismic data from the DOMERAPI temporary seismic network installed in the neighborhood of Merapi and Merbabu volcano. We analyze 53 broad-band seismometers data from October 2013 to mid-April 2015. We also add several stations from MERAMEX network instruments to compare spectrum analysis outside the Merapi and Merbabu volcano. We also removed some tele-seismic and regional events from the data to better analyze the LFPS signal. We have seen a higher amplitude in vertical component near Mt. Merapi and will proceed to analyze all stations.

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Gavrilov, A. M. "A nonlinear method of measuring the amplitude-frequency characteristic of an acoustic emitter." Acoustical Physics 61, no. 4 (July 2015): 407–15. http://dx.doi.org/10.1134/s1063771015030069.

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Chen, Tao, Songbai Xue, Peizhuo Zhai, Bo Wang, and Weimin Long. "Study on Penetration Sensing Method Based on Pool Oscillation and Arc Voltage during Pulsed GMAW." Applied Sciences 10, no. 8 (April 15, 2020): 2735. http://dx.doi.org/10.3390/app10082735.

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The internal relations among the oscillation characteristics of the weld pool, the voltage signal curve and the penetration status of the weld joint in pulsed gas metal arc welding were investigated by using high-speed camera and image analysis system to extract characteristics of weld pool oscillation. The results show that the amplitude of weld pool oscillation decreased with decreasing weld penetration. An abrupt change occurred in the frequency components and amplitude of weld pool oscillation, accompanying the transition from partial to full penetration. The voltage signal curve lost the oscillation frequency characteristic of the pool, due to the curvature of the weld pool surface. While similar to the oscillation amplitude, the fluctuation of the voltage signal caused by the weld pool oscillation reflected the penetration of the weld pool. The abrupt transition in the fluctuation amplitude of the voltage signal in the base duration from partial penetration to full penetration may be used to sense the penetration of the weld pool in real time.

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Belov, Alexey S. "Features of generation and propagation of the extremely low frequency waves excited in the ionosphere under the powerful HF radioemission influence." Physics of Wave Processes and Radio Systems 24, no. 4 (January 16, 2022): 53–62. http://dx.doi.org/10.18469/1810-3189.2021.24.4.53-62.

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The experimental results of the extremely low frequency emission characteristics excited in the outer ionosphere under the ionospheric plasma heating by high-latitude EISCAT facility are presented. The experiments have been conducted in the period of 20062010 yr. using two main schemes of extremely low frequency generation including the impact of the heating facility amplitude modulated emission and two unmodulated pump waves with the frequency detuning. In-situ measurements of the plasma wave disturbances were performed at the outer ionosphere heights using on-board equipment of DEMETER microsatellite. In work the spatial, amplitude and spectral characteristics of the generated extremely low frequency emissions are determined. It is shown that the characteristic size of the extremely low frequency emission is about 400600 km along the trajectory of the DEMETER microsatellite. The registration area spatial position is determined by both the applied generation scheme and the background plasma density distribution. The extremely low frequency emission electric field strength at the Earths outer ionosphere heights is 50330 V/m.

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Altshul, Grigory, Alexander Gouskov, Grigory PanovkoAlexander Shokhin, and Alexander Shokhin. "DYNAMICS FEATURES OF A VIBRATING MACHINE WITH ELASTIC ELEMENT HAVING EXPONENTIAL CHARACTERISTIC OF RESILIENT FORCE." Cybernetics and Physics, Volume 10, 2021, Number 2 (October 1, 2021): 59–62. http://dx.doi.org/10.35470/2226-4116-2021-10-2-59-62.

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The article analyzes the possibility of using nonlinear elastic elements as a suspension of the working element of resonant vibrating machines with two unbalance vibration exciters is analyzed. The elastic characteristic of the suspension is described by an exponential law, which ensures that the natural frequency remains unchanged regardless of the system mass. Static characteristics of the vibration exciter motors are taken into account. A system of differential equations describing movement of the system depending on the processed material mass is obtained. Amplitude-frequency characteristics depending on the power supply voltage, as well as on the debalance rotational speed are obtained for different values of material mass. The stability of the obtained periodic solutions is analyzed. The constancy of resonant amplitude and frequency of the working element vibrations at various values of material mass is shown. The results obtained confirm the advisability of using an equalfrequency suspension of the working element for resonant vibrating machines.

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Wang, Jing, and Jianqiang Sun. "Two types of scale effects on the nonlinear forced vibration of axially moving nanobeams." International Journal of Modern Physics B 34, no. 10 (April 20, 2020): 2050095. http://dx.doi.org/10.1142/s0217979220500952.

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Various non-classical continuum mechanics models appearing in previous studies cannot perfectly explain the mechanical properties of micro- and nanomaterials. Establishing a reasonable continuum mechanics model that comprehensively reflects the scale effect on material deformation is of great practical significance for objectively explaining the variation law of mechanical properties of micro- and nanomaterials under the combined action of different scale effects. Based on nonlocal strain gradient theory, a new scale-dependent model is proposed for axially moving nanobeams. In this study, an asymptotic expansion is performed using the multiscale time method to obtain the amplitude-frequency response curve of the equilibrium solutions for the forced vibration problem. Afterwards, the effects of various system parameters, especially the scale parameters, on the resonance curve are examined. Finally, the effects of nonlocal parameters and material characteristic length parameters on the amplitude-frequency response curves are investigated through typical numerical examples. The numerical results show that the nonlocal parameters promote the emergence of the main resonance, whereas the material characteristic length parameters suppress the emergence of the main resonance. Moreover, these parameters also affect the response amplitude and the skewness and jumping point of the amplitude-frequency characteristic curve.

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CHEN, YANQING, and LIUQING PEI. "ANALYSIS OF THE RECOVERED SIGNAL IN SYNCHRONIZED CHUA’S COMMUNICATION SYSTEM." International Journal of Bifurcation and Chaos 06, no. 08 (August 1996): 1595–600. http://dx.doi.org/10.1142/s0218127496000965.

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The recovered message signal in the synchronized Chua’s system, which is proposed for secure communications, is analyzed by means of both numerical simulations and analytical methods. The results show that the characteristic of “frequency response” of the system is independent of the amplitude of the input message signal, and the amplitude of the recovered signal is suppressed by the system in the lower frequency range and amplified in the higher frequency range. Specifically, we find that, as the frequency of the input signal increases continuously, there is a band of frequency over which a resonance type of phenomenon occurs in the system whereby the input message’s amplitude is amplified, but the location of this band lies beyond the range of the main spectrum of the chaotic driving signal. The phase difference between input signal and output signal is also obtained. Furthermore based on numerical simulations, the characteristic frequency response of a synchronized Lorenz’s system is given, which also shows a band of resonance in the lower range of frequencies.

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Li, Hai Feng, Yu Zhi Luo, Xiao Long Zhang, and Deng Pan. "Vehicle Body and Wheel Motion Simulation Platform Based on LabVIEW." Applied Mechanics and Materials 241-244 (December 2012): 2113–19. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.2113.

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The work in the paper constructed a platform for vehicle’s controllability and stability study conveniently and efficiently. Based on the dynamic model of the two-mass vibration system of vehicle body and wheel, the paper builds a vibration platform using the graphical programming software LabVIEW. It establishes a sinusoidal input road surface model, simulates the sinusoidal road surface under different amplitude and frequencies, and makes it the excitation source of the vibration system. It also obtains the curves of the amplitude-frequency characteristic of vehicle body and wheel displacement on the pavement displacement, and the time-domain response and amplitude-frequency characteristic curve of the body acceleration, suspension spring dynamic deflection and wheel relative dynamic load. This simulation platform provides an intuitive and effective method for vehicle ride comfort both in time domain and frequency domain.

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Brzhezitsky, V. O., Y. O. Haran, A. O. Derzhuk, O. R. Protsenko, Y. O. Trotsenko, and M. M. Dixit. "Ultimate effect of non-identity of capacitive elements of high-voltage arm on frequency characteristics of voltage divider (analytical research)." Electrical Engineering & Electromechanics, no. 4 (July 29, 2021): 46–52. http://dx.doi.org/10.20998/2074-272x.2021.4.06.

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Purpose. Determination in the analytical form of the maximum limiting influence of the non-identity of the capacitive elements of the high-voltage arm on the amplitude-frequency characteristic and phase-frequency characteristic of the voltage divider with parallel-series connection of R-, C-elements of the high-voltage arm. Methodology. Based on the previously developed theory of broadband voltage dividers with parallel-series connection of R-, C-elements, analytical expressions for amplitude-frequency and phase-frequency characteristics of the voltage divider are obtained and investigated taking into account the limit case of non-identical capacitive elements of high-voltage arm. Results. The nature of the dependencies of the frequency characteristics of the broadband voltage divider on the value of the tolerance of the capacitive elements of the high-voltage arm, the division factor of the voltage divider in a wide range of frequency changes is determined. Simplified approximating expressions for the maximum values of frequency characteristics of the voltage divider are proposed and their error is determined. Originality. For the first time in the analytical form the limiting influence of non-identity of capacitive elements of a high-voltage arm of a voltage divider on its frequency characteristics is considered. A mathematical model of this influence is constructed and the limit values of frequency characteristics of the voltage divider are determined. Practical value. It is recommended to introduce into the normative documentation of broadband voltage dividers the corrected value of the division factor, which allows to significantly reduce the deviation of the actual value of the division factor of the voltage divider from the normalized value in a wide range of frequency changes.

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Qiang, Yan, Yingzhou Wang, Lan Luo, Gang Wang, Yuyang Zhao, and Liejiang Wei. "Method for filtering proportional valve-frequency-response test data containing impulsive noise." Advances in Mechanical Engineering 11, no. 3 (March 2019): 168781401983629. http://dx.doi.org/10.1177/1687814019836298.

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Impulsive noise, generated by inverters and other equipment used in the field, tends to easily enter test channels in scenarios where continuous frequency conversion signals are employed to test the frequency response of electrohydraulic proportional valves. Interference caused by such noise reduces the signal-to-response ratio of response signals, thereby influencing the accuracy of the frequency response of proportional valves. To address this concern, in this article, an integrated filtering method that combines ensemble empirical mode decomposition with median filtering is proposed. The proposed method first preprocesses the response signals of the systems and subsequently obtains frequency-response diagrams using fast Fourier transforms. Simulation results demonstrate that the proposed method reduces the root mean square error associated with the amplitude–frequency characteristic curves of the proportional directional valve considered from 2.1 to 0.3, whereas that associated with phase–frequency characteristic curves is reduced from 78.0 to 1.4 with signal-to-noise ratios in the high-frequency band being of the order of –20 dB. Experimental results also reveal that the proposed method reduces the root mean square error of the amplitude–frequency characteristic curves of the proportional directional valve by 52.5% and that of the phase–frequency characteristic curves by 71.2%.

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Xing, Ya Min, Sheng Hu Liu, and Dong Xu Wang. "Design and Research on Piezoelectric Acceleration Geophone." Advanced Materials Research 468-471 (February 2012): 826–30. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.826.

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A kind of piezoelectricity acceleration geophone is studied and discussed. carried on its amplitude frequency, phase-frequency characteristic theoretically, obtained the primary factor of the influence on frequency response, and improved in the piezoelectric crystal choice and geophone structure. The theory and the field test result indicated that, this piezoelectricity acceleration geophone has better response characteristic on low frequency and the high-frequency as well as a higher sensitivity, it is one better detection method.

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Tan, Zong Qi, Hua Ling Zhu, Dao Feng Zhuo, and Ji Feng Ju. "Investigation on Damping Characteristics of Double Chamber Hydro-Pneumatic Suspension Simulation and Experimental Research." Advanced Materials Research 712-715 (June 2013): 1662–67. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1662.

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As to the optimization of double chamber hydro-pneumatic suspension,we researched the influence of excitation signal on the the damping characteristics. First of all, the double chamber hydro-pneumatic suspension nonlinear mathematical model and simulation model were set up to get the damping characteristic curves of different sources.And the influence of different factors was obtained according to the orthogonal test method. The results of the study show that the hydro-pneumatic suspension have nonlinear variable damping characteristics,the excitation signal with higher frequency and larger amplitude have superior damping effect;and the speed of the excitation signal have the biggest influence on its performance.The order of the influence of frequency (f), amplitude (A) and velocity (ν) to suspension performance is: ν>f>A.

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35

Hu, Shi Li, Jian Yong Yang, and Guan Shi Wang. "Attenuation Law of Blasting Seismic Wave Amplitude with Time and Calculation of Equivalent Elastic Modulus." Applied Mechanics and Materials 94-96 (September 2011): 178–85. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.178.

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Abstract. The characteristic frequency was generated when blasting seismic wave propagate in rock mass. The characteristic frequency played an important role in the amplitude attenuation of seismic wave with time and propagation distance. Rock mass was simplified as visco-elastic media. The time attenuation model of seismic wave amplitude was studied by wave equation and the complex number theory. Theoretical analysis demonstrates that attenuation coefficient of seismic wave amplitude with time is mainly affected by rock viscosity coefficient and elastic modulus. The attenuation coefficient decreases with increase of elastic modulus. The attenuation coefficient increases with increase of viscosity coefficient. The test method of equivalent elastic modulus of rock mass was analyzed according to model of time attenuation of seismic wave amplitude in situ. The wave velocity test verified effectiveness of the method. A new method of determining rock mass mechanical parameter was put forward.

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36

Song, Dongli, Yanan Jiang, and Weihua Zhang. "Dynamic performance of a pantograph–catenary system with consideration of the contact surface." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, no. 1 (August 25, 2016): 262–74. http://dx.doi.org/10.1177/0954409716664934.

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The influence of contact surface upon the dynamic performance of a pantograph–catenary system is a question that has been highlighted by the increasing use of high speed railways. Using the mode-superposition method, we establish a pantograph–catenary-coupled dynamics model with consideration of the contact surface; we analyse the characteristics of the contact surface based on a large amount of measured data; and we determine the characteristic parameters according to their influence upon the system dynamic performance. The results show that the contact wire irregularity contains a periodic component formed by gravity and a random component formed by wear, local assembly errors, hardpoints and the like. Periodic and low-frequency random irregularities mainly lead to the increase in contact force amplitude at peak points with wavelengths submultiple of the tension length, span or dropper spacing. On the contrary, high-frequency random irregularity has a great influence upon the amplitude of all frequencies and is the main factor leading to the deterioration of the system dynamic performance. The contact strip wear surface achieves quadratic function fitting, and we propose two characteristic quantities of this surface, namely, shape parameter A, and wear depth B. The wear surface of contact strip enhances the periodic characteristics of pantograph–catenary system of each span, leading to the amplitude increase of the contact force in frequency with span submultiple wavelength. The bigger the absolute value of the shape parameter, the poorer the dynamic performance. According to the criteria of the contact force eigenvalues, we determine the threshold value of the contact strip shape parameter A, and the contact wire irregularity amplitude of each frequency. The threshold given in this paper can be used in the condition assessment of parts, and make judgements on whether a servicing is needed, which is part of the technologies for informationisation and intelligent high-speed train health management.

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Qin, Hong Wu, Hai Fu Li, and Qin Sheng Du. "Analysis Technique for the Spectral Characteristic of Acoustic Emission Signals." Advanced Materials Research 663 (February 2013): 503–6. http://dx.doi.org/10.4028/www.scientific.net/amr.663.503.

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AE method of nondestructive check is based on exertion waves radiation and their registration during fast local material structure reorganization. It is used as a means of analysis of materials, constructions, productions control and diagnosis during operating time. When registering signal amplitude it is required to consider its frequency distribution connecting each amplitude rate with the corresponding vibration rate. With the purpose to reduce the measurement error it is required to perform receiving piezoelectric converters calibration right on the tested unit and in the process of test analysis consider “unit-converter” transfer characteristic.

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Liu, Zhaolun, Guixiang Pan, Jiahao Jiang, and Bin Liu. "Vibration Characteristics of Rolling Mill System under Constraints of the Nonlinear Spring Force and Friction Force from Hydraulic Cylinder." Shock and Vibration 2021 (January 18, 2021): 1–10. http://dx.doi.org/10.1155/2021/6632714.

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Considering the two kinds of nonlinear constraints of rolling mill hydraulic cylinder, spring force and friction force, the vibration model of rolling mill system is established. The amplitude frequency response equations are obtained by using the average method. Comparing the time history curves of vertical vibration displacement of rolling mill system under the nonlinear spring force and friction force, the amplitude frequency characteristic curves are simulated. The external excitation amplitude is viewed as the bifurcation parameter, and the system bifurcation response changing with the external excitation amplitude is analyzed. The influence of the external excitation amplitude on the system stability is studied. The results indicate that the increase of the nonlinear spring force makes the rolling mill system’s unstable area to become wider, and the influence on the rolling mill system of nonlinear friction force behaves as the damping characteristics; the vibration of rolling mill system is alternating between the periodic, period-doubling, and the chaotic motion. The research results provide a theoretical support for restraining the vibration of the rolling mill system in the actual production process.

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Cheng, Ching-Wei, Pei-Hsuan Feng, Jun-Hong Xie, and Yu-Kai Weng. "Eggshell Crack Detection and Egg Classification Using Resonance and Support Vector Machine Methods." Applied Engineering in Agriculture 35, no. 1 (2019): 23–30. http://dx.doi.org/10.13031/aea.12749.

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Abstract. Cracks in eggshells not only affect the egg preservation time but also reduce the success rate for the end-processed products. This study was based on the theory of resonant inspection (RI). The use of the support vector machine (SVM) method as a means of more accurate eggshell crack detection was evaluated. The results revealed that comparing the resonant frequency and amplitude by using a microphone as a sensor allowed non-cracked eggs to be distinguished from cracked eggs. The characteristic frequency of a non-cracked egg was between 4130 and 5500 Hz, and its amplitude was between 0.16 and 0.20 V. The spectrum of a cracked egg was fuzzy, with no obvious characteristic frequency, and the maximum amplitude was approximately 0.06 V. The identification accuracy was 99% and 98% for the SVM training set and testing set, respectively. These results prove that the resonance detection method is effective for identifying eggs with cracked shells. Keywords: Eggshells, Resonant inspection, Fast Fourier transform, Support vector machine.

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40

Marsh, Donald J., Olga V. Sosnovtseva, Alexey N. Pavlov, Kay-Pong Yip, and Niels-Henrik Holstein-Rathlou. "Frequency encoding in renal blood flow regulation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 288, no. 5 (May 2005): R1160—R1167. http://dx.doi.org/10.1152/ajpregu.00540.2004.

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With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation of the myogenic oscillation by TGF. Analysis by wavelet transforms of single-nephron blood flow confirms that both amplitude and frequency of the myogenic oscillation are modulated by TGF. We developed a double-wavelet transform technique to estimate modulation frequency. Median value of the ratio of modulation frequency to TGF frequency in measurements from 10 rats was 0.95 for amplitude modulation and 0.97 for frequency modulation, a result consistent with TGF as the modulating signal. The simulation predicted that the modulation was regular, while the experimental data showed much greater variability from one TGF cycle to the next. We used a blood pressure signal recorded by telemetry from a conscious rat as the input to the model. Blood pressure fluctuations induced variability in the modulation records similar to those found in the nephron blood flow results. Frequency and amplitude modulation can provide robust communication between TGF and the myogenic mechanism.

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41

Legeza, Victor P. "Determination of the Amplitude-Frequency Characteristic of the New Roller Damper for Forced Oscillations." Journal of Automation and Information Sciences 34, no. 5 (2002): 8. http://dx.doi.org/10.1615/jautomatinfscien.v34.i5.40.

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Glinkin, E. I., and E. A. Rukhlova. "DETERMINING THE IMPEDANCE COMPONENTS OF A BIOLOGICAL OBJECT ACCORDING TO THE AMPLITUDE-FREQUENCY CHARACTERISTIC." Tambov University Reports. Series: Natural and Technical Sciences 22, no. 5-2 (2017): 1179–83. http://dx.doi.org/10.20310/1810-0198-2017-22-5-1179-1183.

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43

Liu, Ke, Shulin Tian, and Yindong Xiao. "A method for amplitude-frequency characteristic compensation of signal generator based on pseudo interleaving." JOURNAL OF ELECTRONIC MEASUREMENT AND INSTRUMENT 2009, no. 7 (December 9, 2009): 12–16. http://dx.doi.org/10.3724/sp.j.1187.2009.07012.

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44

Zhao, Chunyu, Bin He, Junjiang Liu, Yanlong Han, and Bangchun Wen. "Design method of dynamic parameters of a self-synchronization vibrating system with dual mass." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 232, no. 1 (January 29, 2017): 3–20. http://dx.doi.org/10.1177/1464419316689643.

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This paper presents a design method of dynamic parameters for the self-synchronization vibrating conveyor with two exciters. The dimensionless coupling equations of the two exciters are derived by using the average method of modified small parameters and the synchronization and stability criteria are deduced from the existence and stability conditions of the dimensionless coupling equations. The two exciters loading coefficient is a periodic function of the phase difference between the two exciters and the extreme point of synchronization is either the minimum or maximum point of the two exciters loading coefficient. There are two ridges in the three-dimensional graphs of the characteristic amplitude and the force transmission coefficient on the plane of the two design frequency ratios, respectively. One ridge of both the characteristic amplitude and the force transmission coefficient is distributed along the curve segment of the one natural frequency ratio in the direction of the working mass frequency ratio approaching to zero, but the other ridge of the characteristic amplitude and that of the force transmission coefficient go along the curve segments of the other natural frequency ratio in the directions that the isolation mass frequency ratio and the working mass frequency ratio approach to infinity, respectively. The design procedure of the dynamic parameters is proposed by numerically and experimentally discussing the effects of the dynamic parameters on the performance parameters of vibrating system. A design example of the vibrating conveyor is given to verify the effectiveness of the proposed design method.

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Li, Yue Hua, and Shi Dong Chen. "Bifurcation Induced by Mass Variation in Piecewise Linear System." Applied Mechanics and Materials 226-228 (November 2012): 531–35. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.531.

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This paper investigates the bifurcations of the periodic solutions in the piecewise linear systems. Firstly the equation about amplitude-frequency response is deduced by the averaging method. Then the bifurcation classification is conducted by applying the singularity theory. The effects of the two parameters, the mass and the excitation amplitude, are discussed. The balance position will be changed when the quality changed, So the system is divided into two kinds of state. The results show that the parameter plane is divided into thirteen regions where bifurcation types are different. At last, discussing the amplitude- frequency response of different regions. this paper provides some theoretical guidance for system of considering load variation, and it is significant to help research the change in amplitude-frequency characteristic of piecewise linear system.

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Tian, Feng, and Hong Jie Si. "The Method of Fast Frequency Response Testing Based on LabVIEW." Applied Mechanics and Materials 433-435 (October 2013): 833–36. http://dx.doi.org/10.4028/www.scientific.net/amm.433-435.833.

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This paper designs a virtual spectrum analyst based on LabVIEW,chirp signal is used for pumping signal of the system. A fast frequency estimation method is realized by the graph programming language LabVIEW. Compared with traditional virtual spectrum analyst, this method can better and faster measure amplitude-frequency characteristic and phase frequency characteristic. The interference factors emerged frequently during the data acquisition were described briefly, and the technology of verification and manipulation of the anomalous signals were studied.

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Meng, Fei, Jien Yang, Peng Song Yang, and Biao Sun. "The Research of Frequency Characteristics of Tracking Differentiator." Applied Mechanics and Materials 182-183 (June 2012): 1474–78. http://dx.doi.org/10.4028/www.scientific.net/amm.182-183.1474.

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Function fhan() and tracking differentiator are important components of Active Disturbance Rejection Control Technique. It is pointed out that function fhan() is not the optimal control synthesis function of discrete system, but function fsun() is. Amplitude and phase frequency characteristic curves of tracking differentiators constructed respectively by function fhan() and fsun() are given by computer simulations. The account formula about turning frequency is also given. Influence of parameter variation on tracking differentiator frequency characteristic is analyszed. The conclusion of this paper is supplement and perfection for the theory of tracking differentiator in Active Disturbance Rejection Control Technique, and it can promote rapid development of Active Disturbance Rejection Control Technique.

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Xu, Yan Chun, Dan Feng Zhao, and Mi Lu. "The Characteristic Parameter Estimation of Low Temperature Target Weak Signal Based on VanderPol-Duffing System." Applied Mechanics and Materials 347-350 (August 2013): 706–10. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.706.

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The weak signal, which is usually submerged in strong noise, is very difficult to detecte for its amplitude and frequency. The dynamic properties of VanderPol-Duffing are studied in this paper. Such system can go into the chaos under certain parameters. In chaotic state the disturbance of weak periodic signals can make the system dynamic behavior change dramatically. Our research results show that the system is from period doubling state to chaotic state when the amplitude of input signal is changed. And it has a remarkable impact influence on the system dynamic performance when the input frequency is varied. The unknown frequency can be detected through counting the numbers of turning point in phase diagram. The simulation results verified that the presented method is feasible and there are a lot of theory values in the research.

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Li, Rui, and Li Xin Guo. "The Research of Vehicle Seat Dynamic Comfort Characteristic." Applied Mechanics and Materials 310 (February 2013): 244–48. http://dx.doi.org/10.4028/www.scientific.net/amm.310.244.

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Increasing consumption of the automobile make vehicle seat comfort characteristic paid more attention to. Damping performance as the third important factors is not allowed to ignore. A three freedom "human - seat" system model has been created for simulation. The result show that as the natural frequency f0 improved, the two resonance peak frequency of the system also improved, the growth of the first order resonance frequency is quite obvious, the second is less growth. And the higher the f0 the less change is. With the improvement of f0, the first order resonance peak to peak value obviously reduced, and the second order resonance peak to peak value increased. So, it is said that the higher the f0 the poor damping effect in high frequency area. The influence of ξ for the damping ratio of work frequency is not big, but the influence for the amplitude value is significant. Increase the natural frequency can make phase angle decreased when resonance, but the change of damping ratio, do not have obviously changes.

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Zeng, Wen, Hong Mei Xia, Yu Xing Wang, and Liu Yi Wang. "Dynamic Characteristic Analysis of Inertial Navigation Platform' Structure." Advanced Materials Research 479-481 (February 2012): 1560–64. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.1560.

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The three-dimensional solid model and finite element model of an inertial navigation platform, is established by using ANSYS software. A modal analysis has been carried out. The former 6 ordered nature frequency and modal shape have been obtained and kept away from the frequency of Laser Gyro. The finite element model of the system vibration is established and is analysed for harmonic response. The calculation data show that vibration amplitude is very small and has no influence for the Laser Gyro working. The theory modal data is the same as the modal test results, so it manifests the accuracy and effectiveness in the modeling and analysis.

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Journal articles on the topic 'Amplitude-frequency characteristic'

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