Frequency-modulated continuous wave(FMCW) laser ranging,which is critical to the laser industry,faces challenges in achieving high range accuracy due to the non-linearity of the laser frequency modulation.Traditional ...Frequency-modulated continuous wave(FMCW) laser ranging,which is critical to the laser industry,faces challenges in achieving high range accuracy due to the non-linearity of the laser frequency modulation.Traditional calibration methods based on iterative algorithms and photoelectric phase-locked loops are limited by their dependence on prior knowledge and often fail to exploit the full potential of the data generated by the ranging system.In this paper,we introduce a novel deep learning approach using digital twin(DT) technology,demonstrating the potential in fields such as aerospace and optics.We propose a neural network(NN) model integrated with the soft actor-critic(SAC) control algorithm operating within a DT framework to effectively calibrate the nonlinear errors during the frequency-swept process.This innovative framework has significantly improved the performance of FMCW laser ranging,with the side mode suppression ratio(SMSR) of the beat signal increasing from 3.2 to 17.3 d B and the full width at half-maximum(FWHM) decreasing from 15.82 to 2.64 kHz.These improvements not only enhance the accuracy and quality of the FMCW ranging system but also pave the way for new research directions and insights in the broader fields of optical society.展开更多
Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.Howe...Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.However,two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect.Firstly,the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers.Secondly,the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately.These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation.Based on the digital signal sampling property,the square coefficients and cross-coupling coefficients of accelerometers are considered.Meanwhile,the asymmetry scale factors are considered in the I-F conversion unit.Thus,a nonlinear model of specific force measurement is established compared to the linear model.Based on the three-axis turntable,the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers.Considering the nonlinear combination,the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure.Besides,an efficient specific force calculation model is approximately derived to reduce the real-time computation cost.Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients.The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.展开更多
It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate ...It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.展开更多
基金supported by the Baima Lake Laboratory Joint Fund of Zhejiang Provincial Natural Science Foundation of China (No.LBMHY25F030002)the Zhejiang Provincial Natural Science Foundation of China (No.LY23F050001)+1 种基金the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China (No.LZY24F050002)the Municipal Government of Quzhou (No.2024D012)。
文摘Frequency-modulated continuous wave(FMCW) laser ranging,which is critical to the laser industry,faces challenges in achieving high range accuracy due to the non-linearity of the laser frequency modulation.Traditional calibration methods based on iterative algorithms and photoelectric phase-locked loops are limited by their dependence on prior knowledge and often fail to exploit the full potential of the data generated by the ranging system.In this paper,we introduce a novel deep learning approach using digital twin(DT) technology,demonstrating the potential in fields such as aerospace and optics.We propose a neural network(NN) model integrated with the soft actor-critic(SAC) control algorithm operating within a DT framework to effectively calibrate the nonlinear errors during the frequency-swept process.This innovative framework has significantly improved the performance of FMCW laser ranging,with the side mode suppression ratio(SMSR) of the beat signal increasing from 3.2 to 17.3 d B and the full width at half-maximum(FWHM) decreasing from 15.82 to 2.64 kHz.These improvements not only enhance the accuracy and quality of the FMCW ranging system but also pave the way for new research directions and insights in the broader fields of optical society.
基金Project(61174002)supported by the National Natural Science Foundation of ChinaProject(200897)supported by the Foundation of National Excellent Doctoral Dissertation of PR China+1 种基金Project(NCET-10-0900)supported by the Program for New Century ExcellentTalents in University,ChinaProject(131061)supported by the Fok Ying Tung Education Foundation,China
文摘Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.However,two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect.Firstly,the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers.Secondly,the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately.These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation.Based on the digital signal sampling property,the square coefficients and cross-coupling coefficients of accelerometers are considered.Meanwhile,the asymmetry scale factors are considered in the I-F conversion unit.Thus,a nonlinear model of specific force measurement is established compared to the linear model.Based on the three-axis turntable,the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers.Considering the nonlinear combination,the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure.Besides,an efficient specific force calculation model is approximately derived to reduce the real-time computation cost.Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients.The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.
文摘It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.
