Precise differential travel-time measurement is essential for earthquake relative locating.The waveform cross correlation(WCC)technique is widely regarded as the most effective method for calculating the differential ...Precise differential travel-time measurement is essential for earthquake relative locating.The waveform cross correlation(WCC)technique is widely regarded as the most effective method for calculating the differential travel-time of seismic phases.However,for earthquake pairs with large magnitude differences,substantial biases can arise due to disparities in the duration of the initial pulse,potentially leading to significant mislocations,particularly for mainshocks.To overcome this limitation,we propose to use the dynamic time warping(DTW)algorithm to optimize differential travel-time calculation.Using high-quality earthquake waveform data from the San Andreas Fault(2012−2019),we systematically compared the performance of DTW and WCC,respectively.Our results demonstrate that DTW substantially improves differential travel-time measurements,especially in cases involving large magnitude differences.In addition,we tested the robustness of DTW using noisy seismic data,demonstrating its superior resilience to noise.展开更多
This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relativ...This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relative motion dynamics model,a prescribed time output feedback control strategy is proposed.A prescribed-time extended state observer is designed to estimate the relative velocity and external disturbances.The disturbance estimates are then used as the feedforward component of the controller.Building on this framework,a novel prescribed-time active disturbance rejection control strategy for position tracking is developed via a backstepping control design.The convergence of the extended state observer and the stability of the closed-loop system are rigorously analyzed using Lyapunov stability theory.Numerical simulations are performed to validate the effectiveness of the proposed controller.展开更多
Efficient multiple unmanned aerial vehicles(UAVs)path planning is crucial for improving mission completion efficiency in UAV operations.However,during the actual flight of UAVs,the flight time between nodes is always ...Efficient multiple unmanned aerial vehicles(UAVs)path planning is crucial for improving mission completion efficiency in UAV operations.However,during the actual flight of UAVs,the flight time between nodes is always influenced by external factors,making the original path planning solution ineffective.In this paper,the multi-depot multi-UAV path planning problem with uncertain flight time is modeled as a robust optimization model with a budget uncertainty set.Then,the robust optimization model is transformed into a mixed integer linear programming model by the strong duality theorem,which makes the problem easy to solve.To effectively solve large-scale instances,a simulated annealing algorithm with a robust feasibility check(SA-RFC)is developed.The numerical experiment shows that the SA-RFC can find high-quality solutions within a few seconds.Moreover,the effect of the task location distribution,depot counts,and variations in robustness parameters on the robust optimization solution is analyzed by using Monte Carlo experiments.The results demonstrate that the proposed robust model can effectively reduce the risk of the UAV failing to return to the depot without significantly compromising the profit.展开更多
In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-...In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-view (FOV) constraints based on biased proportional navigation guidance (PNG) is developed in this paper. The remaining flight time (time-to-go) estimation method is derived considering aerodynamic force and gravity. The number of differential equations is reduced and the integration step is increased by changing the integral variable, which makes it possible to obtain time-to-go through integration. An impact time controller with FOV constraints is proposed by analyzing the influence of the biased term on time-to-go and FOV constraint. Then, numerical simulations are performed to verify the correctness and superiority of the method.展开更多
In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the p...In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the position information of the target,which will lose energy.In this paper,a long time integration method of radar signal based on rotating target radon Fourier transform(RTRFT)is proposed.This method modifies the distance and frequency terms in the traditional generalized radon Fourier transform(GRFT),and adds the frequency sinusoidal modulation term.Then,based on the cardinality balanced multi-target multi-Bernoulli(CBMeMBer)filter,the position of the target is detected in the high-dimensional space obtained by RTRFT.This method can combine coherent integration and micro-motion parameter estimation.Simulation experiments show that the proposed method can estimate the main translational parameters and rotational micro-motion parameters of the target while detecting the target,and the target detection performance is improved.展开更多
A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization ...A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing.展开更多
基金Projects(42204067,42574117,42130810)supported by the National Natural Science Foundation of ChinaProject(2024JJ6495)supported by the Natural Science Foundation of Hunan Province,China。
文摘Precise differential travel-time measurement is essential for earthquake relative locating.The waveform cross correlation(WCC)technique is widely regarded as the most effective method for calculating the differential travel-time of seismic phases.However,for earthquake pairs with large magnitude differences,substantial biases can arise due to disparities in the duration of the initial pulse,potentially leading to significant mislocations,particularly for mainshocks.To overcome this limitation,we propose to use the dynamic time warping(DTW)algorithm to optimize differential travel-time calculation.Using high-quality earthquake waveform data from the San Andreas Fault(2012−2019),we systematically compared the performance of DTW and WCC,respectively.Our results demonstrate that DTW substantially improves differential travel-time measurements,especially in cases involving large magnitude differences.In addition,we tested the robustness of DTW using noisy seismic data,demonstrating its superior resilience to noise.
文摘This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relative motion dynamics model,a prescribed time output feedback control strategy is proposed.A prescribed-time extended state observer is designed to estimate the relative velocity and external disturbances.The disturbance estimates are then used as the feedforward component of the controller.Building on this framework,a novel prescribed-time active disturbance rejection control strategy for position tracking is developed via a backstepping control design.The convergence of the extended state observer and the stability of the closed-loop system are rigorously analyzed using Lyapunov stability theory.Numerical simulations are performed to validate the effectiveness of the proposed controller.
基金supported by the National Natural Science Foundation of China(72571094,72271076,71871079)。
文摘Efficient multiple unmanned aerial vehicles(UAVs)path planning is crucial for improving mission completion efficiency in UAV operations.However,during the actual flight of UAVs,the flight time between nodes is always influenced by external factors,making the original path planning solution ineffective.In this paper,the multi-depot multi-UAV path planning problem with uncertain flight time is modeled as a robust optimization model with a budget uncertainty set.Then,the robust optimization model is transformed into a mixed integer linear programming model by the strong duality theorem,which makes the problem easy to solve.To effectively solve large-scale instances,a simulated annealing algorithm with a robust feasibility check(SA-RFC)is developed.The numerical experiment shows that the SA-RFC can find high-quality solutions within a few seconds.Moreover,the effect of the task location distribution,depot counts,and variations in robustness parameters on the robust optimization solution is analyzed by using Monte Carlo experiments.The results demonstrate that the proposed robust model can effectively reduce the risk of the UAV failing to return to the depot without significantly compromising the profit.
基金supported by the National Natural Science Foundation of China(U21B2028).
文摘In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-view (FOV) constraints based on biased proportional navigation guidance (PNG) is developed in this paper. The remaining flight time (time-to-go) estimation method is derived considering aerodynamic force and gravity. The number of differential equations is reduced and the integration step is increased by changing the integral variable, which makes it possible to obtain time-to-go through integration. An impact time controller with FOV constraints is proposed by analyzing the influence of the biased term on time-to-go and FOV constraint. Then, numerical simulations are performed to verify the correctness and superiority of the method.
文摘In the traditional radar unmanned aerial vehicle(UAV)detection process,coherent integration and micro-Doppler(m-D)parameter estimation are carried out separately.The target discrimination process needs to obtain the position information of the target,which will lose energy.In this paper,a long time integration method of radar signal based on rotating target radon Fourier transform(RTRFT)is proposed.This method modifies the distance and frequency terms in the traditional generalized radon Fourier transform(GRFT),and adds the frequency sinusoidal modulation term.Then,based on the cardinality balanced multi-target multi-Bernoulli(CBMeMBer)filter,the position of the target is detected in the high-dimensional space obtained by RTRFT.This method can combine coherent integration and micro-motion parameter estimation.Simulation experiments show that the proposed method can estimate the main translational parameters and rotational micro-motion parameters of the target while detecting the target,and the target detection performance is improved.
基金This project was supported by the National Natural Science Foundation of China (60472102)Shanghai Leading Academic Discipline Project (T0103).
文摘A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing.
