Papers by Keyword: Phase Difference

Abstract: Fatigue tests have been carried out to investigate the effects of mean-stress and phase-difference on the tension-torsion fatigue failure of 2A12-T4 aluminum alloy. The results show that for fully reversed tension-torsion loading, the fatigue life increases with the increase of phase angle, but the fatigue life decreases with the increase of phase angle, when mean-stress exists, both for shear mean-stress and normal mean-stress. Fracture appearance shows that the crack initiation is on the direction of maximum shear stress amplitude plane. Critical plane criteria based on the linear combination of the maximum shear stress amplitude and maximum normal stress are studied and further discussion on the drawbacks of this kind of criteria are performed.

Abstract: There is a bias drift of silicon microgyroscope when power on which limits its application in higher precision field. This paper analyzes and validates the main cause of bias drift, combined with theoretical analysis of demodulation and experimental results, which has a great significance for improving the performance of silicon microgyroscope. First of all, operating principle of silicon microgyroscope is introduced and theoretical analysis on bias drift is made on the basis of DC output voltage of microgyroscope. Secondly, demodulated signals’ amplitude and phase are analyzed in Matlab with the experimental data. By contrasting theoretical and experimental bias drift, the accuracy of theoretical formula is verified. It turns out that, the relative error of bias drift from 2-hours value to stable value is 5.5%, it’s 6.6% for 1-hour value to stable value and for beginning it’s just 1.7%. Experimental results agrees well with the theoretical analysis, which verifies that the main cause of bias drift of silicon microgyroscope is the phase difference between Vds and Vsense. This conclusion can provide some guidance for structure design optimization and circuits improving.

Abstract: According to the demand of accuracy detection of the motor energy efficiency, the hardware of testing bench for motor based on torque-meter method was designed. A design emphasis on loading equipment and torque sensor was introduced in accordance with the requirements of torque meter method, realized the rapid response of the load, the low speed stability of the work and electrical energy reutilization. The proposed error modification method ensured the accuracy and reliability of test results.

Abstract: Classic RAKE demodulator(RAKEDE), multi-carrier coherent RAKEDE and RAKEDE with two antennas are given in the paper. According to those schemes provided, the G_SNR, which means the gain of signal to noise ratio (SNR), for those three kinds of RAKEDE is derived, and the closed form of the expression for G_SNR of those three kinds of RAKEDE is given in the paper. Comparing with those performance evaluation methods of RAKEDE existed, the method derived in this paper on the basis of diversity reception is more usable and easy to be accept.

Abstract: This paper expounded the principle of using Fast Fourier transform measuring the phase difference and completed the simulation of measuring the phase differences of a plurality of signal. The simulation results show that the method can rapidly and accurately realize the phase difference measurement without considering the AD quantization error and noise interference. In considering the AD quantization error and random noise, Fast Fourier transform measuring the phase difference still has high measurement accuracy, and the measurement error can be controlled within 0.01°. The method can be applied in practical engineering.

Abstract: The output signal of the free-drive three-axis MEMS gyroscope used in Spinning Projectiles contains rolling is sine period signal. In order to demodulate the yawing and pitching angular rates, extracting the fringe phase information is needed. It is difficult to realize the phase demodulation of single signal. To solve this problem, reference signal is provided. The phase of the gyroscope is extracted by computing the phase difference. Then, three methods of phase difference measurement are introduced and simulated by MATLAB. According to the signal feature, the contrastive analysis of measurement error is made and the maximal precision of measuring method for phase difference is obtained. The last part is the analysis of performance.

Abstract: To reduce the hardware cost of traditional multichannel array or interferometer, a direction finding method using rotated long baseline interferometer (RLBI) has been developed. To overcome the initialization problem, a multiple hypothesis Gauss-Newton (MHGN) algorithm is proposed. It first chooses multiple initial pairs from a pair of PD measurements and then applies each value to the GN algorithm and meanwhile obtains a cost for this initial value. Finally, the ultimate estimate is then picked with the minimum cost. Simulation shows that the proposed method can approach to the Cramer-Rao lower bound (CRLB).

Abstract: Recently, study of transparent materials, such as thin film form, have an important field for the development of advanced electronic devices. Therefore, the need for the precision thermal property measurement techniques of transparent thin film materials becomes increasing according to the development of these material. The ideal methods for optically measurements of these properties are noncontact method. However, optically measurements are often difficult due to the transparency. So, transparent materials have not enough temperature gradient in the air layer above thin films. To solve this problem, we used the collinear deflection method which is one of the photothermal deflection methods. In the measurement process, both of the pump beam and probe beam are irradiated vertically on the transparent sample. And the probe beam is deflected by refractive index variation of samples due to the temperature gradient inside samples.The purpose of this study is to analyze the effect of thermal and optical properties analytically on the collinear deflection method for variable materials.

Abstract: Based on the small scale power system frequency fluctuation frequency leakage problems due to the FFT phase measurement error problem, this paper presents a high accuracy algorithm for phase difference measurement based on windowed discrete Fourier transform, the signal truncated using 4 order Blackman-Harris window, and corrects the phase correction method for discrete spectrum thus to calculate the phase difference. The algorithm for phase difference measurement theory and signal frequency independent, so there is no need to sample the signals of the whole cycle. A simple algorithm, less calculation, high precision, has strong inhibition on the harmonic and noise, simulation results verify the feasibility and effectiveness of the algorithm.

Abstract: In the laser interferometer system based on the four quadrants photoelectric, phase difference between two quadrants photoelectric is the way of identifying the fringe width and rotating angle, in order to achieving the measurement of two-dimensional small angle. Due to the temperature instability of the laser itself, the system installation error, the electronic device noise, and wave-front error etc, interference fringes prone to bending, and the received optical signal contains unequal amplitude and DC offset error, which will have a serious impact on measurement. Therefore, this paper analysis these impact of the wave-front error on the interferometer system and propose improvement measures. New hardware circuit is designed to eliminate the DC offset and the new algorithm based on multiple linear regression models is proposed to achieve the high-precision extraction of phase difference. The experiment results show that the methods reach the angle accuracy 0.1 arc second.