Papers by Keyword: Phase Difference

Abstract: The paper presents the digital phase measuring instrument based on MSP430 single-chip microcomputer. The instrument adopted the technology of DDS to generate sinusoidal signal, and FPGA to achieve phase difference measurement and polarity judgment. The system is composed of a filtering circuit, a phase shifting network, a shaping circuit, matrix keyboard, LCD display module and the frequency is in the range from 200Hz to 10kHz, the phase difference is in the range of-180°~+180 °, the resolution ratio is 0.1°, the absolute error is less than ±2 °, and the relative error is less than ± 3%.

Abstract: In this work, we proposed a new calibration of piezoelectric phase-shifter using probability analysis based on Two-dimensional Fourier transform profilometry (2-D FTP). We tested the surface of the object under the noisy condition using the newly designed simulation system. It is found that both the relative and the absolute error are much less than those from the traditional method.

Abstract: Moving-magnet linear compressors with sensorless top dead center (TDC) control method are an efficient solution for domestic refrigerators to save energy. TDC can be determined by the inflection point of phase difference between the sinusoidal current and piston displacement (I-X phase difference). A digital correlation method is used to calculate the I-X phase difference to obtain the TDC position for control. The TDC determining system using digital correlation method is manufactured and the error is 2.29% under various discharge pressures.

Abstract: To meet the high real-time performance and high accuracy requirements of signal detection in the rail splicing process, this paper proposes a new type of magnetic grid rail splicing method based on accurately zeroing output signal phase difference of two magnetic grid reading heads, thus establishing two reading heads “shift” rules. The accurate zero setting technology of phase difference is based on Nuttall window algorithm, which doesn’t need to give the exact signal frequency beforehand and sample periodically, and can effectively eliminate phase errors. So this algorithm is suitable for detecting signal phase difference when reading heads go over buff joints with any speed at any initial position. Additionally, simulation test and experimental verification were performed on this detection algorithm and “shift” rules. The results show that, the method mentioned in this paper can real-time detect the phase difference by “shift” rules, when reading heads go over buff joints with any speed or any acceleration.

Abstract: This paper, aiming at rigid-continuous girder bridge with high piers, uses the large mass method (LMM) to analyze the seismic response of such special structure under a series of different phase differences by considering both rigid foundation and elastic foundation models. In addition, this paper discusses the influence rules for extreme response of different parts of structure due to traveling wave effect. The result shows that traveling wave effect greatly affects the rigid-continuous girder bridge with high piers. When considering the traveling wave effect, the internal force of bridge piers presents increasing trend, and the displacement of pier top reduces with increasing phase differences. The internal force and extreme displacement response of bridge structure present cyclical variations with phase differences, and that cycle is consistent with the characteristic period of bridge.

Abstract: The discreteness of device parameters exists in the analog signal processing using conventional phase measurement methods, and the error caused by threshold voltage of comparator is difficult to estimate and eliminate. Due to this shortcoming, a method based on TMS320F28335 eCAP module for measuring the phase difference is presented. Firstly, the AC signal is amplified and filtered to eliminate the error introduced by electromagnetic interference, and then the digital signal through the Schmitt Trigger designed by CPLD is converted to wave signal with the same frequency of the signal, by capturing the edge-triggered, enters the capture interruption subroutine to calculate the number of the sampling points of one period, finally the phase difference is calculated according to correlation method. Hardware circuit and software flow chart are given. The experimental results verify the method has higher reliability and precision than conventional methods.

Abstract: By analyzing the nonlinear characteristic of phase difference of receiving VLF signal in Xinxiang. Research on it's chaotic characteristic and probability of predicting it take advantage of the chaotic theory. The numerical results show that the phase difference of propagation has chaotic characteristic on the position that has specified latitude and longitude. Predicting the phase difference by using the method that based on the lyapunov exponent. The standard deviation and variance of Prediction results are 1.6240 cec and 2.6375 cec, respectively.

Abstract: This paper proposes the traffic signal optimization design for the street crosswalk between coordinated adjacent intersections. The design has taken the pedestrian waiting tolerance limit time into consideration as one of the constraint conditions to obtain the pedestrian green phase duration. If the green phase duration is not sufficient for pedestrian crossing safety, the methods of twice crossing street or two chances of crossing can be applied according to different situations. The common red time of two intersections is analyzed to build delay functions by using of motorcade dispersion and traffic flow rate relationship, and timing optimization parameter can be worked out to minimize the total vehicle delay, thus determining signal phase difference. The result shows that this design may ensure the pedestrian safety and reduce the pedestrian delay.

Abstract: In order to investigate the effect of friction on gear system featuring confluence transmission, a non-linear dynamic model of three-gear system having two gear pairs was built. The influence of gear systems dynamic characteristics caused by changing of friction coefcient was researched. With the changing of friction coefcient, left-right gear pairs show dynamic behavior with coexist of same periodic motion, coexist of different periodic motion and chaos. With the increase of friction coefcient, the jump phenomenon of amplitude occurred, the impact of gear system became larger.

Abstract: This paper introduces a new position method based on phase difference. The electrocircuits are designed to meet the position demand. The signal produced, phase demodulation, drive circuit are described. Lots of experiments are performed to test the linear error, hysteresis error, repeatability error and stability error. The uncertainty is synthesized based on testing data and the results show that the displacement error form electrocircuits is less than 11.2nm.