The performance of vehicle suspension is evaluated based on three conflicting indexes:body acceleration,suspension deflection,and dynamic tire load,which vary across different frequency bands.The suspension control st...The performance of vehicle suspension is evaluated based on three conflicting indexes:body acceleration,suspension deflection,and dynamic tire load,which vary across different frequency bands.The suspension control strategy faces the challenge to strike a balance among these indexes.This research analyzes the fundamental mechanism of control phase deviation effects on skyhook damper control,groundhook damper control,and acceleration drive damper control.From the perspective of complex domain mechanical impedance with the support of the inertial suspension,a structure-based compensation approach is proposed to address for the control phase deviation.The simulation analysis demonstrates that the coordination of inertial suspension structure and control strategy can effectively enhance the comprehensive suspension performance across entire frequency range.Finally,a semi-active inertial suspension bench is implemented.The experimental results indicate that the suspension with the semi-active inertial suspension has outstanding vibration isolation ability,and enhances the suspension performance at ride comfort,suspension deflection,and road friendly significantly.展开更多
The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnos...The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.展开更多
Combined with the advantages and disadvantages of tuned liquid damper (TLD) and tuned mass damper (TMD),a double tuned liquid mass damper (TLMD) is proposed by replacing the rigid connection of TLD with the spring str...Combined with the advantages and disadvantages of tuned liquid damper (TLD) and tuned mass damper (TMD),a double tuned liquid mass damper (TLMD) is proposed by replacing the rigid connection of TLD with the spring structure.The motion equation of a single-degree-of-freedom structure with a TLMD attached at its top is found under harmonic excitation.Comparing the energy consumption and amplitude of primary structure with equal mass ratio TMD,it is found that the energy dissipation performance of TLMD is better in the effective phase region.The interaction process between TLMD and structure is analyzed,and the formula of phase deviation between the relative velocity of tank and the displacement of primary structure is deduced.By analyzing the influence of mass ratio,frequency ratio,damping ratio and water depth ratio on the damping effect,the results show that the frequency ratio and liquid depth ratio have great influence on the size and location of deep resonance peak,and the mass ratio and damping ratio have great influence on the width of the effective frequency band.The formula of equivalent damping ratio is proposed based on the principle of energy and it is found that the equivalent damping ratio is related to the phase deviation and change with the frequency ratio of the external excitation.展开更多
Navigation satellites generally use satellite-ground and inter-satellite observation data for precise orbit determination.In orbit determination,the satellite position is often referenced to the satellite’s centroid,...Navigation satellites generally use satellite-ground and inter-satellite observation data for precise orbit determination.In orbit determination,the satellite position is often referenced to the satellite’s centroid,while the observational measurements are referenced to the satellite’s antenna phase center.The deviation between the satellite’s centroid and the antenna phase center forms the satellite antenna phase center error,which affects the precision of orbit determination.This paper takes a global navigation satellite system(GNSS)MEO satellite as an example and analyzes the actual situation of the satellite antenna phase center deviation and phase center variation based on the ground calibration data of the in-orbit satellite antenna phase center and the satellite’s in-orbit working status.The analysis shows that the antenna phase center variation caused by the satellite’s in-orbit operation is only at the centimeter level,which has a limited impact on orbit determination accuracy.The main source of precise orbit determination error is the satellite antenna phase center deviation,which can be corrected using ground calibration data.展开更多
Time-frequency methods are effective tools in identifying the frequency content of a signal and revealing its timevariant features.This paper presents the use of instantaneous features(i.e.,instantaneous energy and si...Time-frequency methods are effective tools in identifying the frequency content of a signal and revealing its timevariant features.This paper presents the use of instantaneous features(i.e.,instantaneous energy and signal phase)of acoustic emission(AE)in the detection of thermal damage to the workpiece in grinding.The low-order frequency moments of a scalogram are used to obtain both the instantaneous energy and the mean frequency at which the signal phase is recovered.The grinding process is monitored using AE for a variety of operating conditions,including regular grinding,grinding at higher cutting speed and larger feed,and small dressing depth of cut.The instantaneous features extracted by the scalogram are compared with the results obtained by the empirical mode decomposition.It has been found that both the instantaneous energy and phase deviation indicate the presence of burn damage and serve as robust and reliable indicators,providing a basis for detecting the grinding burn.展开更多
Due to the rapid development of electronic countermeasures(ECMs),the corresponding means of electronic counter countermeasures(ECCMs)are urgently needed.In this paper,an act-ive anti-jamming method based on frequency ...Due to the rapid development of electronic countermeasures(ECMs),the corresponding means of electronic counter countermeasures(ECCMs)are urgently needed.In this paper,an act-ive anti-jamming method based on frequency diverse array radar is proposed.By deriving the closed form of the phase center in a uniform line array FDA,we establish a model of the FDA signal based on adaptive weights and derive the effect of active anti-jamming in this regime.The pro-posed active anti-jamming method makes it difficult for jammers to detect or locate our radar.Fur-thermore,the effectiveness of the two frequency increment schemes in terms of anti-jamming is ana-lyzed by comparing the deviation of phase center.Finally,the simulation results verify the effective-ness and superiority of the proposed method.展开更多
Phasor measurement units(PMUs)provide useful data for real-time monitoring of the smart grid.However,there may be time-varying deviation in phase angle differences(PADs)between both ends of the transmission line(TL),w...Phasor measurement units(PMUs)provide useful data for real-time monitoring of the smart grid.However,there may be time-varying deviation in phase angle differences(PADs)between both ends of the transmission line(TL),which may deteriorate application performance based on PMUs.To address that,this paper proposes two robust methods of correcting time-varying PAD deviation with unknown parameters of TL(ParTL).First,the phenomena of time-varying PAD deviation observed from field PMU data are presented.Two general formulations for PAD estimation are then established.To simplify the formulations,estimation of PADs is converted into the optimal problem with a single ParTL as the variable,yielding a linear estimation of PADs.The latter is used by second-order Taylor series expansion to estimate PADs accurately.To reduce the impact of possible abnormal amplitude data in field data,the IGG(Institute of Geodesy&Geophysics,Chinese Academy of Sciences)weighting function is adopted.Results using both simulated and field data verify the effectiveness and robustness of the proposed methods.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52202471)the National Natural Science Foundation of China:Regional Innovation and Development Joint Fund(Grant No.U20A20331)+2 种基金Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant No.2022ZB659)the National Natural Science Foundation of China(Grant No.52002156 and 52072157)the Postgraduate Education Reform Project of Jiangsu Province(Grant No.KYCX21_3333).
文摘The performance of vehicle suspension is evaluated based on three conflicting indexes:body acceleration,suspension deflection,and dynamic tire load,which vary across different frequency bands.The suspension control strategy faces the challenge to strike a balance among these indexes.This research analyzes the fundamental mechanism of control phase deviation effects on skyhook damper control,groundhook damper control,and acceleration drive damper control.From the perspective of complex domain mechanical impedance with the support of the inertial suspension,a structure-based compensation approach is proposed to address for the control phase deviation.The simulation analysis demonstrates that the coordination of inertial suspension structure and control strategy can effectively enhance the comprehensive suspension performance across entire frequency range.Finally,a semi-active inertial suspension bench is implemented.The experimental results indicate that the suspension with the semi-active inertial suspension has outstanding vibration isolation ability,and enhances the suspension performance at ride comfort,suspension deflection,and road friendly significantly.
基金supported by the National Natural Science Foundation of China under Grant No.61371049
文摘The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.
基金the National Natural Science Foundation of China(Nos.51578434 and 51378500)。
文摘Combined with the advantages and disadvantages of tuned liquid damper (TLD) and tuned mass damper (TMD),a double tuned liquid mass damper (TLMD) is proposed by replacing the rigid connection of TLD with the spring structure.The motion equation of a single-degree-of-freedom structure with a TLMD attached at its top is found under harmonic excitation.Comparing the energy consumption and amplitude of primary structure with equal mass ratio TMD,it is found that the energy dissipation performance of TLMD is better in the effective phase region.The interaction process between TLMD and structure is analyzed,and the formula of phase deviation between the relative velocity of tank and the displacement of primary structure is deduced.By analyzing the influence of mass ratio,frequency ratio,damping ratio and water depth ratio on the damping effect,the results show that the frequency ratio and liquid depth ratio have great influence on the size and location of deep resonance peak,and the mass ratio and damping ratio have great influence on the width of the effective frequency band.The formula of equivalent damping ratio is proposed based on the principle of energy and it is found that the equivalent damping ratio is related to the phase deviation and change with the frequency ratio of the external excitation.
文摘Navigation satellites generally use satellite-ground and inter-satellite observation data for precise orbit determination.In orbit determination,the satellite position is often referenced to the satellite’s centroid,while the observational measurements are referenced to the satellite’s antenna phase center.The deviation between the satellite’s centroid and the antenna phase center forms the satellite antenna phase center error,which affects the precision of orbit determination.This paper takes a global navigation satellite system(GNSS)MEO satellite as an example and analyzes the actual situation of the satellite antenna phase center deviation and phase center variation based on the ground calibration data of the in-orbit satellite antenna phase center and the satellite’s in-orbit working status.The analysis shows that the antenna phase center variation caused by the satellite’s in-orbit operation is only at the centimeter level,which has a limited impact on orbit determination accuracy.The main source of precise orbit determination error is the satellite antenna phase center deviation,which can be corrected using ground calibration data.
文摘Time-frequency methods are effective tools in identifying the frequency content of a signal and revealing its timevariant features.This paper presents the use of instantaneous features(i.e.,instantaneous energy and signal phase)of acoustic emission(AE)in the detection of thermal damage to the workpiece in grinding.The low-order frequency moments of a scalogram are used to obtain both the instantaneous energy and the mean frequency at which the signal phase is recovered.The grinding process is monitored using AE for a variety of operating conditions,including regular grinding,grinding at higher cutting speed and larger feed,and small dressing depth of cut.The instantaneous features extracted by the scalogram are compared with the results obtained by the empirical mode decomposition.It has been found that both the instantaneous energy and phase deviation indicate the presence of burn damage and serve as robust and reliable indicators,providing a basis for detecting the grinding burn.
基金the National Natural Science Foundation of China(No.61971438)the Natural Science Founda-tion of Shaanxi Province(No.2019JM-155).
文摘Due to the rapid development of electronic countermeasures(ECMs),the corresponding means of electronic counter countermeasures(ECCMs)are urgently needed.In this paper,an act-ive anti-jamming method based on frequency diverse array radar is proposed.By deriving the closed form of the phase center in a uniform line array FDA,we establish a model of the FDA signal based on adaptive weights and derive the effect of active anti-jamming in this regime.The pro-posed active anti-jamming method makes it difficult for jammers to detect or locate our radar.Fur-thermore,the effectiveness of the two frequency increment schemes in terms of anti-jamming is ana-lyzed by comparing the deviation of phase center.Finally,the simulation results verify the effective-ness and superiority of the proposed method.
基金This work was supported by the National Key Research and Development Program of China(2017YFB0902901)National Natural Science Foundation of China(51627811).
文摘Phasor measurement units(PMUs)provide useful data for real-time monitoring of the smart grid.However,there may be time-varying deviation in phase angle differences(PADs)between both ends of the transmission line(TL),which may deteriorate application performance based on PMUs.To address that,this paper proposes two robust methods of correcting time-varying PAD deviation with unknown parameters of TL(ParTL).First,the phenomena of time-varying PAD deviation observed from field PMU data are presented.Two general formulations for PAD estimation are then established.To simplify the formulations,estimation of PADs is converted into the optimal problem with a single ParTL as the variable,yielding a linear estimation of PADs.The latter is used by second-order Taylor series expansion to estimate PADs accurately.To reduce the impact of possible abnormal amplitude data in field data,the IGG(Institute of Geodesy&Geophysics,Chinese Academy of Sciences)weighting function is adopted.Results using both simulated and field data verify the effectiveness and robustness of the proposed methods.
