Applied Mechanics and Materials Vols. 568-570

Abstract: The least square algorithms were widely used in the estimation of localizing and tracing situation in military fields. In this paper, we proposed a method of using a full rank matrix instead of using singular value decomposition to solving the non-full rank matrix. Therefore the improving least square (ILS) algorithm was emerged at this situation. The simulation results show that the proposed tracing algorithm exhibits higher accuracy compared with the least square algorithm. This new method can take full application of the measured information to improved the tracing accuracy in the whole controlled area.

Abstract: In asynchronous sampling, discrete Fourier transform (DFT) spectrum involves errors. Scholars have done great investigations on the correction techniques of DFT spectrum, but the errors have not been completely eliminated all along. In this paper, spectrums were examined from the principle of conservation of energy. It is unnoticed before that the energy of the digital signal, which is the analysis object of DFT, isn't equal to that of the finite continuous signal truncated by rectangular window. Thus the energy of their spectrums are different according to the Parseval's theorem. The Energy Loss-Gain (ELG) error was introduced to express the energy difference between these two spectrums. The ELG error is zero if the observed continuous signal is truncated in integral multiple of half cycle and it is related to the cycle number and sampling number in one cycle. Analysis show that the ELG error decreases with the increment of these two parameters, which are helpful to the engineering.

Abstract: The Doppler frequency shift of the signal received from receiver carrier in high dynamic environment which means high speed and high acceleration represents different changing rules. The changing rules can make the positioning accuracy become worse and even make the receiver unable to track the signal. On the basis of modeling and simulation of three high dynamic carriers including the aircraft, satellite and ballistic missile, the changing rules of Doppler frequency shift were analyzed using the calculation equation of the Doppler frequency shift. The results show that for the high dyanmic carriers, the larger the velocity of the carrier is, the larger corresponding Doppler frequency shift is and the larger the acceleration of the carrier is, the larger corresponding changing rate of Doppler frequency shift is.

Abstract: After introducing the ambiguity function theory of radar analysis, wideband ambiguity function about Direct Spread/Frequency Hopping (DS/FH) signal is derived out in this paper. From the point of signal simulation ambiguity figure, the tracking performance is studied and analyzed, that includes ambiguity character and signal resolution under the influence of frequency switching time and phase discontinuous. Conclusion shows the following design difficulty based on feasibility in DS/FH TT&C.

Abstract: A class of the balanced biorthogonal multiwavelets was constructed by defining a specific matrix filter structure, in which the multifilter banks of multiwavelets have had the desired symmetry. Here, the multifilter banks have possess symmetric/antisymmetric, which resembled filters of scalar wavelet and have in favor of application, notwithstanding the multiwavelets constructed in this paper have lost the linear phase, so they have formed a new type of multiwavelets undoubtedly.

Abstract: Discrete Fourier transform (DFT/FFT) spectrums contain a variety of inherent errors in asynchronous sampling. Spectrum analysis with the accuracy above 10^-3 are generally challenging issues. This work divides the DFT procedure into four signal transforms and exams six spectrum errors originated from these distortions. Besides the review of traditional errors, a so-called energy loss-gain (ELG) error is briefly introduced, which is proved to be a considerable error on the basis of Parseval's theorem. With the help of full error analysis mentioned here and the further development of analytical error estimators, it is expectable to obtain a DFT spectrum with a specified accuracy.

Abstract: A High-Speed LVDS Data Acquisition system is designed, with XILINX’s Virtex-5 FPGA as core processor as well as TI’s TMS320C6748 DSP for pre-processing and storing data. This system achieved a greater amount of image processing and faster image processing requirement. The system completed the dual LVDS image data acquisition according to the demand. The resolution of the image data is 320x257. Each image transmission frame rate of not less than 150 / sec. large amount of data throughout the system as well as real-time demanding is a big challenge for designer. The designer uses simulation tools from Mentor Graphics Hyperlynx to complete the stack and impedance calculation and signal quality simulation to ensure that the system is stable and reliable. This system also has better scalability and more reliable storage method than past designs. Recently, the system has completed testing verification and results show that this design is feasible and reliable.

Abstract: Using power spectrum density estimation method, analyzed the digital observational data of water-tube tiltmeters of Shaanxi deformation monitoring network in 6 seismic stations as QL, HZ, HY, BJ, XA and NQ, which detected the earth’s free oscillations stimulated by the Mw8.3 Okhotsk Sea Earthquake in May 24th, 2013. The results show that radical shock of spherical oscillation (₀S₀₅~₀S₃₂), harmonic spherical oscillation (₃S₀₁, ₁S₀₄, ₂S₀₄, ₁S₀₆) and toroidal oscillations (₀T₀₅~₀T₀₉) are detected effectively. Comparing the period of the extracted oscillation with that the theoretical oscillation of the Preliminary Reference Earth Model (PREM), finding that they are accordant with each other and the relative error is less than 0.2%. And the result is consistent with the CDSN Urumqi observatory recorded in M8.1 Kunlun Mountains Earthquake in 2001.

Abstract: A data acquisition and control system for a safety valve test bench with high pressure and large flow rate, was developed based on the host-slave architecture, which takes an Industrial Personal Computer (IPC) as host computer and a Programmable Automatic Controller (PAC) as salve computer. The hardware architecture and software design of this system were introduced in detail. This system was verified by the experiment, and the results indicate that it can fulfill the requirement of data acquisition and control with high speed and long distance. This study can provide reference for many automation control fields.

Abstract: The aliasing error resulted from truncating signals incoherently is one of main spectrum errors. The investigation on the error remains quite limited. This restricted the development of high accuracy spectrum analysis. This work discussed the truncation effect and the corresponding aliasing error in quantity, and revealed its dependence upon the truncation conditions. Then a concise technique was proposed to suppress the truncation aliasing error of DFT spectrum by modifying the first datum of the digital signal in time domain. Under general truncation conditions, the simulations show that the error correction of the 5 spectral lines near the main lobe is effective and the maximum absolute error of the main spectral line is decreased from ±2.4‰ to ±0.5‰.