Transfer alignment is used to initialize SINS(Strapdown Inertial Navigation System)in motion.Lever-arm effect compensation is studied existing in an AUV(Autonomous Underwater Vehicle)before launched from the mother sh...Transfer alignment is used to initialize SINS(Strapdown Inertial Navigation System)in motion.Lever-arm effect compensation is studied existing in an AUV(Autonomous Underwater Vehicle)before launched from the mother ship.The AUV is equipped with SINS,Doppler Velocity Log,depth sensor and other navigation sensors.The lever arm will cause large error on the transfer alignment between master inertial navigation system and slave inertial navigation system,especially in big ship situations.This paper presents a novel method that can effectively estimate and compensate the flexural lever arm between the main inertial navigation system mounted on the mother ship and the slave inertial navigation system equipped on the AUV.The nonlinear measurement equation of angular rate is derived based on three successive rotations of the body frame of the master inertial navigation system.Nonlinear filter is utilized as the nonlinear estimator for its capability of non-linear approximation.Observability analysis was conducted on the SINS state vector based on singular value decomposition method.State equation of SINS was adopted as the system state equation.Simulation experiments were conducted and results showed that the proposed method can estimate the flexural lever arm more accurately,the precision of transfer alignment was improved and alignment time was shortened accordingly.展开更多
This paper presents a novel SINS/IUSBL integration navigation strategy for underwater vehicles.Based on the principle of inverted USBL(IUSBL),a SINS/IUSBL integration navigation system is established,where the USBL de...This paper presents a novel SINS/IUSBL integration navigation strategy for underwater vehicles.Based on the principle of inverted USBL(IUSBL),a SINS/IUSBL integration navigation system is established,where the USBL device and the SINS are both rigidly mounted onboard the underwater vehicle,and fully developed in-house,the integration navigation system will be able to provide the absolute position of the underwater vehicle with a transponder deployed at a known position beforehand.Furthermore,the state error equation and the measurement equation of SINS/IUSBL integration navigation system are derived,the difference between the position calculated by SINS and the absolute position obtained by IUSBL positioning technology is used as the measurement information.The observability of the integration system is analyzed based on the singular value decomposition(SVD)method.Finally,a mathematical simulation is performed to demonstrate the effectiveness of the proposed SINS/IUSBL integration approach,and the observable degrees of the state variables are also analyzed.展开更多
Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is p...Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is proposed to reduce the phase error caused by the nonlinear response of a digital projector in the three-dimensional measurement system of fringe structured light.According to the analysis of the influence of Gamma distortion on the phase calculation,the algorithm establishes the relationship model between phase error and harmonic coefficient,introduces phase shift to the signal,and keeps the signal amplitude constant while filtering out the DC component.The phase error is converted to the transform domain,and compared with the numeric value in the space domain.The algorithm is combined with a spiral phase function to optimize the Hilbert transform,so as to eliminate external noise,enhance the image quality,and get an accurate phase value.Experimental results show that the proposed method can effectively improve the accuracy and speed of phase measurement.By performing phase error compensation for free-form surface objects,the phase error is reduced by about 26%,and about 27%of the image reconstruction time is saved,which further demonstrates the feasibility and effectiveness of the method.展开更多
The observation vectors in traditional coarse alignment contain random noise caused by the errors of inertial instruments,which will slow down the convergence rate.To solve the above problem,a real-time noise reductio...The observation vectors in traditional coarse alignment contain random noise caused by the errors of inertial instruments,which will slow down the convergence rate.To solve the above problem,a real-time noise reduction method,sliding fixed-interval least squares(SFI-LS),is devised to depress the noise in the observation vectors.In this paper,the least square method,improved by a sliding fixed-interval approach,is applied for the real-time noise reduction.In order to achieve a better-performed coarse alignment,the proposed method is utilized to de-noise the random noise in observation vectors.First,the principles of proposed SFI-LS algorithm and coarse alignment are devised.A simulation test and turntable experiment were executed to demonstrate the availability of the designed method.It is indicated that,from the results of the simulation and turntable tests,the designed algorithm can effectively reduce the random noise in observation vectors.Therefore,the proposed method can enhance the performance of coarse alignment availably.展开更多
Misalignment angle error model describing the SINS mathematical platform error is presented in this paper following the idea of small misalignment angle error model and large azimuth misalignment angle error model.It ...Misalignment angle error model describing the SINS mathematical platform error is presented in this paper following the idea of small misalignment angle error model and large azimuth misalignment angle error model.It can be considered that the three misalignment angles are independent of the rotational sequence in the misalignment error model,but not suitable in the large misalignment error model.The error angle of Euler platform is used to represent the three misalignment angles from theoretical navigation coordinate system to computational navigation coordinate system.The Euler platform error angle is utilized to represent the mathematical platform error and its physical meaning is very clear.The SINS nonlinear error model is deduced by using the error angle of Euler platform and is simplified under the condition of large azimuth error and small error.The simplified results are more comprehensive and accurate than the large azimuth misalignment error model.The damping SINS algorithm and its error model are proposed to change the structure of the strapdown inertial navigation algorithm by using the external damping information.The accuracy of SINS error model of large Euler platform error angle is simulated,and has strong practicability in initial alignment and is conducive to reducing the amount of calculation.展开更多
A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissi...A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissibility functions of theundamaged signals and the damage signals at different points are calculated. Secondly,the difference between them is taken as the damage index. Finally, principal componentanalysis (PCA) is used to reduce the noise feature. And then, input to the online sequencelimit learning neural network classification to identify damage and confirm the damagelocation. Taking the amplitude of the transmissibility function instead of the accelerationresponse as the signal analysis for structural damage identification cannot be influencedby the excitation amplitude. The OS-ELM algorithm is based on the ELM (ExtremeLearning Machine) algorithm, in-creased training speed also increases the recognitionaccuracy. Experiment in the epoxy board shows that the method can effectively identifythe structural damage accurately.展开更多
基金This work is funded by Natural Science Foundation of Jiangsu Province under Grant BK20160955a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions and Science Research Foundation of Nanjing University of Information Science and Technology under Grant 20110430+1 种基金Open Foundation of Jiangsu Key Laboratory of Meteorological Observation and Information Processing(KDXS1304)Open Foundation of Jiangsu Key Laboratory of Ocean Dynamic Remote Sensing and Acoustics(KHYS1405).
文摘Transfer alignment is used to initialize SINS(Strapdown Inertial Navigation System)in motion.Lever-arm effect compensation is studied existing in an AUV(Autonomous Underwater Vehicle)before launched from the mother ship.The AUV is equipped with SINS,Doppler Velocity Log,depth sensor and other navigation sensors.The lever arm will cause large error on the transfer alignment between master inertial navigation system and slave inertial navigation system,especially in big ship situations.This paper presents a novel method that can effectively estimate and compensate the flexural lever arm between the main inertial navigation system mounted on the mother ship and the slave inertial navigation system equipped on the AUV.The nonlinear measurement equation of angular rate is derived based on three successive rotations of the body frame of the master inertial navigation system.Nonlinear filter is utilized as the nonlinear estimator for its capability of non-linear approximation.Observability analysis was conducted on the SINS state vector based on singular value decomposition method.State equation of SINS was adopted as the system state equation.Simulation experiments were conducted and results showed that the proposed method can estimate the flexural lever arm more accurately,the precision of transfer alignment was improved and alignment time was shortened accordingly.
基金The author would like to thank the support in part by the National Natural Science Foundation of China(Grant No.51375088)Inertial Technology Key Lab Fund,the Fundamental Research Funds for the Central Universities(2242015R30031,2242018K40065,2242018K40066)the Foundation of Shanghai Key Laboratory of Navigation and Location Based Services.
文摘This paper presents a novel SINS/IUSBL integration navigation strategy for underwater vehicles.Based on the principle of inverted USBL(IUSBL),a SINS/IUSBL integration navigation system is established,where the USBL device and the SINS are both rigidly mounted onboard the underwater vehicle,and fully developed in-house,the integration navigation system will be able to provide the absolute position of the underwater vehicle with a transponder deployed at a known position beforehand.Furthermore,the state error equation and the measurement equation of SINS/IUSBL integration navigation system are derived,the difference between the position calculated by SINS and the absolute position obtained by IUSBL positioning technology is used as the measurement information.The observability of the integration system is analyzed based on the singular value decomposition(SVD)method.Finally,a mathematical simulation is performed to demonstrate the effectiveness of the proposed SINS/IUSBL integration approach,and the observable degrees of the state variables are also analyzed.
基金This work is funded by the Scientific and Technological Projects of Henan Province under Grant 152102210115.
文摘Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is proposed to reduce the phase error caused by the nonlinear response of a digital projector in the three-dimensional measurement system of fringe structured light.According to the analysis of the influence of Gamma distortion on the phase calculation,the algorithm establishes the relationship model between phase error and harmonic coefficient,introduces phase shift to the signal,and keeps the signal amplitude constant while filtering out the DC component.The phase error is converted to the transform domain,and compared with the numeric value in the space domain.The algorithm is combined with a spiral phase function to optimize the Hilbert transform,so as to eliminate external noise,enhance the image quality,and get an accurate phase value.Experimental results show that the proposed method can effectively improve the accuracy and speed of phase measurement.By performing phase error compensation for free-form surface objects,the phase error is reduced by about 26%,and about 27%of the image reconstruction time is saved,which further demonstrates the feasibility and effectiveness of the method.
基金This work was supported in part by the Inertial Technology Key Lab Fund 614250607011709in part by the Fundamental Research Funds for the Central Universities 2242018K40065,2242018K40066in part by the Foundation of Shanghai Key Laboratory of Navigation and Location Based Services,Key Laboratory Fund for Underwater Information and Control 614221805051809.
文摘The observation vectors in traditional coarse alignment contain random noise caused by the errors of inertial instruments,which will slow down the convergence rate.To solve the above problem,a real-time noise reduction method,sliding fixed-interval least squares(SFI-LS),is devised to depress the noise in the observation vectors.In this paper,the least square method,improved by a sliding fixed-interval approach,is applied for the real-time noise reduction.In order to achieve a better-performed coarse alignment,the proposed method is utilized to de-noise the random noise in observation vectors.First,the principles of proposed SFI-LS algorithm and coarse alignment are devised.A simulation test and turntable experiment were executed to demonstrate the availability of the designed method.It is indicated that,from the results of the simulation and turntable tests,the designed algorithm can effectively reduce the random noise in observation vectors.Therefore,the proposed method can enhance the performance of coarse alignment availably.
基金This work is funded by Natural Science Foundation of Jiangsu Province under Grant BK20160955a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions and Science Research Foundation of Nanjing University of Information Science and Technology under Grant20110430+1 种基金Open Foundation of Jiangsu Key Laboratory of Meteorological Observation and Information Processing(KDXS1304)Open Foundation of Jiangsu Key Laboratory of Ocean Dynamic Remote Sensing and Acoustics(KHYS1405).
文摘Misalignment angle error model describing the SINS mathematical platform error is presented in this paper following the idea of small misalignment angle error model and large azimuth misalignment angle error model.It can be considered that the three misalignment angles are independent of the rotational sequence in the misalignment error model,but not suitable in the large misalignment error model.The error angle of Euler platform is used to represent the three misalignment angles from theoretical navigation coordinate system to computational navigation coordinate system.The Euler platform error angle is utilized to represent the mathematical platform error and its physical meaning is very clear.The SINS nonlinear error model is deduced by using the error angle of Euler platform and is simplified under the condition of large azimuth error and small error.The simplified results are more comprehensive and accurate than the large azimuth misalignment error model.The damping SINS algorithm and its error model are proposed to change the structure of the strapdown inertial navigation algorithm by using the external damping information.The accuracy of SINS error model of large Euler platform error angle is simulated,and has strong practicability in initial alignment and is conducive to reducing the amount of calculation.
文摘A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissibility functions of theundamaged signals and the damage signals at different points are calculated. Secondly,the difference between them is taken as the damage index. Finally, principal componentanalysis (PCA) is used to reduce the noise feature. And then, input to the online sequencelimit learning neural network classification to identify damage and confirm the damagelocation. Taking the amplitude of the transmissibility function instead of the accelerationresponse as the signal analysis for structural damage identification cannot be influencedby the excitation amplitude. The OS-ELM algorithm is based on the ELM (ExtremeLearning Machine) algorithm, in-creased training speed also increases the recognitionaccuracy. Experiment in the epoxy board shows that the method can effectively identifythe structural damage accurately.
