JVE International
Not a member yet
1200 research outputs found
Sort by
Efficient FPGA-based FIR – architecture and its significance in ultrasonic signal processing
Get PDFThe presented work demonstrates the most suitable architecture for the FPGA-based signal processing which makes available various real-time filtering algorithms, such as band pass, high pass, low pass, and band-reject for FIR filters. The processor was implemented with the fixed-point arithmetic using VHDL, which can be downloadable on FPGA device. The FPGA device can be interfaced with an analog-to-digital converter (ADC), digital-to-analog converter (DAC) and a personal computer with MATLAB for the user interface and feeding coefficients and order of the filter. The core part of this paper was to find the reconfigurable and efficient architecture of the processor with only one multiplier which can work for Finite Impulse response (FIR) filter with the best- suited structure. The system will be used for automatic generation of fixed-point FIR filters. The model was also implemented in MATLAB script and the verification of results in the case of low-pass filtering confirmed that both models in MATLAB and VHDL matched to each other. All components of architecture in VHDL were designed using generics which allow changing its structure and behavior by generic values. Therefore, it is a universal filter platform where user can process the data while changing the filter parameters as per the requirement of applications. The complete design was verified by taking the example of audio signal frequency, but parameterized components of system architecture can also facilitate its applicability at ultrasonic frequencies by changing the algorithm. The significance and applicability of FPGAs in ultrasonic signal processing were also studied and reviewed
Dynamics analysis of the pitch control reducer for MW wind turbine
Get PDFAn analytic dynamics model was presented for the three-stage planetary transmission in the pitch control reducer for MW wind turbine based on the lumped-parameter method. The mechanical characteristic of the contact components was analyzed using the stiffness factor method. All the stiffness sub-matrices were combined to form the overall stiffness matrix of the three-stage transmission. According to the analytic model and the parameters of the pitch control gearbox, the movement differential equations were solved to investigate the natural frequencies and the vibration modes. Then, the undamped and damping forced vibration response were studied. A test rig was set up to measure the vibration displacement of the ring at the second stage and the output shaft under the nominal load condition, the comparison of the analytic forced vibration response with the experimental results validates the effectiveness of the lumped-parameter dynamics model for the pitch control reducer. This paper provides a reference for the dynamics optimization of multistage planetary transmission
Study on acoustic target strength characteristics of underwater composite rudder
Get PDFIn order to investigate the acoustic behavior of composite material, in this paper, the acoustic target strength (TS) of rudders is obtained by combining the finite element method with the automatically matched layer technique. However, besides the composite material mentioned above, the considered materials of rudder models also include steel. In addition, the results of abeam direction and other angles are computed. Finally, the magnitude of abeam TS versus frequency shows that the acoustic scattering property of composite model is better than that of steel one when the frequency is higher than 1600 Hz. Moreover, the acoustic scattering properties are totally different when frequency is lower than 600 Hz for models with composite and steel materials. As for directivity patterns, the TS of composite model in each direction is lower than that of steel model at 3800 Hz, which matches the conclusions mentioned above
Test and analysis of three axis vibration of harmonic drives
Get PDFA new vibration testing method is introduced to measure three-axis vibration of harmonic drives used in industrial robots. To simulate the working state of industrial robots, a harmonic drive loading device was designed. In the case of loading, the vibration of a harmonic drive in three axes was measured. Experimental data was used to evaluate the vibration performance, analyze the vibration characteristics of the harmonic drive, and determine the cause of the vibration abnormality. The research results showed that the presented measuring method is helpful to monitor the vibration performance of harmonic drives, and control the quality of the product
Axisymmetric scattering of a fluid spheroid illuminated by an acoustical Bessel beam
Get PDFDepending on the partial wave series expression, the scattering of a fluid spheroid illuminated by a zeroth-order Bessel beam is calculated in the spherical coordinate. For a fluid spheroid, the scattering is associated with the host medium, and the immersed spheroid medium. Although spherical and cylinder fluid objects has been discussed a lot before, a prolate and oblate fluid spheroid has not been investigated deeply. In the paper, two limited boundary conditions (Neumann and Dirichlet) are presented and discussed about far-field scattering form functions. By comparing these two limited conditions, the analysis could be applied into underwater detection and acoustic tweezers, or other fields. For other fluid materials, this method could also be utilized to calculate and analyze
Research on consumption prediction of spare parts based on fuzzy C-means clustering algorithm and fractional order model
Get PDFIn order to achieve the non-stationary de-noising signal effectively, and to solve the prediction of less sample, a hybrid model composed of FCCA (Fuzzy C-means clustering algorithm) and FOM (Fractional Order Model) was constructed. The degree of each data point was determined by FCCA to de-noise and the p order cumulative matrix was extended to r fractional cumulative matrix, so that the fractional order cumulative grey model was established to make forecasting. The results of numerical example showed that the hybrid model can obtain better prediction accuracy
Research on dynamic characteristics of spiral basilar membrane after replacing artificial auditory ossicle based on the reconstructed human ear model
Get PDFIn this paper, PATRAN software was used to establish a complete 3D finite element model of human ears, and it was then combined with NASTRAN software to analyze frequency responses. This paper conducted a detailed analysis on the dynamic parameters including umbo and stapes displacements of normal human ears under sound pressures 90 dB and 105 dB. The numerically computational results were compared with experimental data. When the analyzed frequency was less than 1000 Hz, the computational result of numerical simulation was well consistent with the upper limit. When the analyzed frequency was more than 1000 Hz, the computational result of numerical simulation was well consistent with the lower limit. Therefore, the numerically computational model was reliable. In addition, based on the verified model, this paper studied vibration characteristics of spiral basilar membrane after replacing artificial auditory ossicle based on the whole hearing system, and found that vibration characteristics of spiral basilar membrane had an obvious change at low and high frequencies after replacing artificial auditory ossicle TORP. Using finite element method to analyze vibration characteristics of spiral basilar membrane can well predict the hearing recovery effect after replacing artificial auditory ossicle. Compared with normal ears, the vibration level of spiral basilar membrane after replacing artificial auditory ossicle has slowed down in 100 Hz-600 Hz, 2000 Hz-4000 Hz and 7000 Hz-10000 Hz, and has been strengthened in 600 Hz-2000 Hz and 4000 Hz-7000 Hz, which provided some help for the hearing recovery at the high-frequency band
EEMD-Based cICA method for single-channel signal separation and fault feature extraction of gearbox
Get PDFThis paper proposes a novel fault feature extraction method with the aim of extracting the fault feature submerged in the single-channel observation signal. The proposed method integrates the strengths of the constrained independent component analysis (cICA) extracting only the signals of interest (SOIs) with the advantage of ensemble empirical mode decomposition (EEMD) alleviating the mode mixing. The method, which is named EEMD-based cICA, not only enables gear fault feature extraction but also offers a new independent component analysis (ICA) mixing model with source noise and measured noise for the single-channel observation signal. The efficiency of the proposed method is tested on simulated as well as real-world vibration signals acquired from a multi-stage gearbox with a missing tooth and a chipped tooth, respectively
Adaptive mesh refinement method for optimal control based on Hermite-Legendre-Gauss-Lobatto direct transcription
Get PDFDirect transcription has been employed to transcribe the optimal control problem into a nonlinear programming problem. This paper presents a trajectory optimization method based on a combination of the direct transcription and mesh refinement algorithm. Hermite-Simpson method has the advantage of reasonable accuracy with highly sparse Hessian matrix and constraint Jacobians, and the pseudospectral method provides spectral accuracy for optimal control problems. The optimal control problem is discretized at a series of Legendre-Gauss-Lobatto points, then the trajectory states are approximated by using local Hermite interpolating polynomials. Thus, the method produces significantly smaller mesh size with a higher accuracy tolerance solution. The derived relative error estimation is then used to trade the number of mesh polynomials degree within each mesh interval with the number of mesh intervals. As a result, the suggested method can produce more small mesh size, requires less computation solution for the same optimal control problem. The simulation experiment results show that the suggested method has many advantages
Study on aerodynamic characteristics and running safety of two high-speed trains passing each other under crosswinds based on computer simulation technologies
Get PDFWith the continuously increased running speed of high-speed trains, aerodynamic problems become more and more obvious. Running safety of trains under crosswinds is a serious problem among numerous aerodynamic problems. Aiming at this problem, this paper combines computational fluid dynamics with multi-body dynamics to study aerodynamic characteristics and safety problems when the high-speed train is running under crosswinds. Based on fluid software FLUENT, this paper computes the flow field of two high-speed trains passing each other under crosswinds. Meanwhile, with combining the multi-body dynamic software SIMPACK with theories, the paper establishes a multi-body dynamic model of the high-speed train, and applies random aerodynamic loads which act on the high-speed train to this model. Impacts of aerodynamic forces (force moments) on aerodynamic characteristics and running safety of each train compartment in the open air are analyzed. Analyzed results show that: when two high-speed trains are passing each other at the same speed of 350 km/h and the crosswind speed is 15 m/s, maximum pressure fluctuations are at observation points near the lateral windows of the head train; aerodynamic forces and force moments of the head train are more than those of the mid-train and tail-train; the high-speed train still has a high safety performance under crosswinds, where the maximum derailment coefficient is 1.9, the reduction rate of the wheel load is 1.1 and the overturning coefficient is 0.98, all of which are smaller than the limit value. More comprehensive factors are considered by the computational model in this paper. It can be used as an effective method to study and evaluate the performance of two high-speed trains passing each other under crosswinds