Amplitude phase control for electro-hydraulic servo system based on normalized least-mean-square adaptive filtering algorithm

The electro-hydraulic servo system was studied to cancel the amplitude attenuation and phase delay of its sinusoidal response,by developing a network using normalized least-mean-square (LMS) adaptive filtering algorithm.The command input was corrected by weights to generate the desired input for the algorithm,and the feedback was brought into the feedback correction,whose output was the weighted feedback.The weights of the normalized LMS adaptive filtering algorithm were updated on-line according to the estimation error between the desired input and the weighted feedback.Thus,the updated weights were copied to the input correction.The estimation error was forced to zero by the normalized LMS adaptive filtering algorithm such that the weighted feedback was equal to the desired input,making the feedback track the command.The above concept was used as a basis for the development of amplitude phase control.The method has good real-time performance without estimating the system model.The simulation and experiment results show that the proposed amplitude phase control can efficiently cancel the amplitude attenuation and phase delay with high precision.

Evaluation of underground blast-induced ground motions through nearsurface low-velocity geological layers

Surface ground motion produced by underground blasts is significantly influenced by near-surface geological conditions.However,near-surface low-propagation velocity layers were always ignored in past analyses of ground motions due to their thin thickness.With the rising concern about surface ground motions produced by the ascendant scale and frequentness of underground excavation and mining,close attention is gradually paid to ground blast vibrations.Therefore,systemic experiments were conducted and took seven months in an underground mine to clarify the variation of motion from underground rock to surface ground.The attenuation of surface ground peak particle velocities(PPVs)is compared to that in underground rock,and horizontal amplitudes are compared to vertical amplitudes.Differences between bedrock and surface ground vibrations are analyzed to illustrate the site effect of near-surface lower-propagation velocity layers.One-dimensional site response analysis is employed to quantify the influence of different geological profiles on surface ground vibrations.The experimental data and site response analysis allowed the following conclusions:(1)geological site effects mainly produce decreasing dominant frequency(DF)of surface ground vibrations;(2)the site amplification effect of blast vibration needs to be characterized by peak particle displacement(PPD);(3)shear waves(S-waves)begin to dominate and surface Rayleigh waves(R-waves)develop as blast-induced ground vibrations travel upward through rock and lower-velocity layers to the surface.The comparison of response relative displacement to a critical value is best to assess the potential for cracking on surface structures.

Study of errors in ultrasonic heat meter measurements caused by impurities of water based on ultrasonic attenuation

Impurity is one of the main factors that affect the measurement accuracy of an ultrasonic heat meter. To study the effects of different impurity species and concentrations on the accuracy of heat meters, flow tests were carried out for the suspending of calcium carbonate and yellow mud. By analyzing the attenuation characteristics of the ultrasound amplitude in different impurity concentrations and species, the influence of the impurities on the heat meter measurement accuracy is evaluated. In order to avoid the inaccuracy caused by the sediment of the reflective bottom surface, a vortex generator is put ahead of the reflective surface. According to the test, the calcium carbonate suspension with a mass concentration of 1%, which influences the heat meter accuracy severely, is used as the flow media. The influence of the vortex generator on the calcium carbonate suspension flow field in the heat meter body is studied with numerical simulations. The results of this paper provide some theoretical guide on improving the heat meter measurement accuracy when the water contains impurities.

Variable optical attenuators with ability to independently control two orthogonal linearly polarized light amplitudes

New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.

Q Inversion and Comparison of Influential Factors among Three Methods: CFS, SR, and AA

The goals of this study were to examine factors influencing Q inversion and to provide references for practical application.Three different methods for inverting Q values with VSP data were explored,including centroid frequency shift(CFS),spectral ratio(SR),and amplitude attenuation(AA).Comparison between the CFS and the other two methods was conducted on frequency band widths and low attenuation,wavefield components,interface interference,and thin layers.Results from several sets of VSP modeling data indicated that the CFS method is more stable and accurate for dealing with thin and high Q layers.Frequency band width,especially the presence of high frequencies,influences the inversion effect of all three methods.The wider the band,the better the results.Q inversion from downgoing wavefield was very similar to that of the upgoing wavefield.The CFS method had fewer outliers or skip values from the full wavefield than the other two methods.Moreover,the applications to Q inversion for the set of field VSP data demonstrated that the Q curves from the CFS method coincided with the geological interpretations better than the Q curves of the other methods.Meanwhile,inverse Q filtering shifted the frequency component from 25 Hz to 35 Hz.The results demonstrated that the Q curve is more sensitive to geological horizons than velocity.