Showing papers in "Journal of Chinese Inertial Technology in 2010"

Application of adaptive Kalman filter technique in initial alignment of inertial navigation system

Abstract: To improve the alignment precision and convergence speed of strap-down inertial navigation system,an initial alignment method based on Sage-Husa adaptive filter is proposed.The exactitude alignment error model and the adaptive Kalman filter equation are derived for the case of small misalignment azimuth angle.When the noise statistical characteristics are known,the Kalman filter is suitable;while in the active system,most noise statistical characteristics are unknown,so we introduce an adaptive filter.It use the information of observations on-line estimation and correct the noise statistical characteristics,makes the system has a higher filtering effect.Through simulation verifiable,the adaptive Kalman filter algorithm,improve the convergence speed and alignment accuracy effectively.

Attitude matching method for ship deformation measurement

Abstract: A new algorithm using attitude matching method is proposed for ship deformation measurement system based on ring laser gyro units(LGUs).In the new algorithm,the Kalman filter measurements are set up based on the two LGUs' real-time attitude information which is different from the inertial measurement matching method.Each of the LGUs systems directly uses the ring laser gyros' outputs to update its attitude with respect to the inertial space,and the inertial frame is chosen to be the initial LGU frame,which can avoid the initial alignment problems and make full use of ring laser gyros' high angle measurement precision.Simulation results show that high frequency and accurate ship deformation measurement can be effectively realized,and the simulated measurement precision can be higher than 15″,which lays a sound fundation for actual application of ship deformation measurement based on LGUs.

Error analysis and calibration of systematic dual-axis rotation-modulating SINS

Abstract: The SINS based on Rotation-modulation technology can reduce the effect of constant drift of Inertial Instruments,and effectively improve the long-time navigation accuracy.To develop a SINS based on the Rotation-modulation technology,a scheme of systematic dual-axis Rotation-modulating SINS(RSINS)based on the basic principle of RSINS is presented,and its long-time navigation error characteristic is simulated and analyzed.The main errors which cause the long-time navigation error are found,and a systematic self-calibration scheme is presented which can calibrate those errors only with its own rotating frame.Finally,the systematic calibration scheme is tested by computer simulation.The result shows that the main errors,which cause the long-time navigation error,can be estimated accurately,and it is a feasible method.

Feedforward compensation method for three axes inertially stabilized platform imbalance torque

Abstract: Three axes inertially stabilized platform is used to stabilize the imaging sensor in airborne high-resolution remote sensing system.But due to the existence of mass imbalance in three axes inertially stabilized platform,the imbalance torque is inevitable under the effect of acceleration,which could lead to the decline of platform accuracy and the degeneration of image quality.In order to attenuate the influence of the imbalance torque,an observer-based imbalance torque feed-forward compensation method is proposed.Firstly,an imbalance torque observer is designed to estimate the real-time imbalance torque.Then,through feed-forward compensation,the influence of imbalance torque is restrained.The simulation results show that the platform stable accuracy is dramatically improved,and the effectiveness of the observer-based imbalance torque feed-forward compensation method is obvious.

Measurement-based adaptive kalman filtering algorithm for GPS/INS integrated navigation system

Abstract: To solve the problem that traditional adaptive filtering algorithms are inaccurate and unreliable in estimating the GPS measurement noises of GPS/INS integrated navigation system,a measurement-based adaptive Kalman filtering algorithm(MAKF) is put forward.Based on the complementary measuring characteristics of GPS/INS and the short-term high-precision features of INS,this algorithm can get the adaptive estimation of GPS measurement noises.The simulation results show that the MAKF,which can real-time track the GPS time-varying measurement noises and modify the observation error covariance matrix R,is superior to the improved sage-husa kalman filtering in filtering precision and stability.And it can effectively overcome the divergence of improved sage-husa adaptive filtering algorithm for the integrated navigation system,especially when with lower-precision gyro.

Summary on technology of automatic landing/carrier landing

Abstract: With so wicked international environment,it is very important to build strong national defence.To maintain stability for the areas around us,a strong maritime power is needed.Research on aircraft carrier has been a hotspot.In this paper,the advantage and the development of landplane and carrier plane are introduced and compared.Then the researches on landing technology of plane are discussed from two aspects of landing tracks and navigation ways.Finally the paper gives the prospect of the technology of automatic landing,and puts forward 4 aspects of developments for further researching,and mainly points out that using the information fusion technology to fuse the sensors,including vision,radar and others,is inevitable trend for plane landing technology.

Comparison between transfer alignments of inertial navigation system in two coordinates

Abstract: The error transfer models of inertial navigation system(INS) in launch-point inertial coordinate and local geographical coordinate are built respectively,and the transfer alignment algorithms (such as "velocity + attitude","angular velocity + acceleration) in these two coordinates are derived and applied respectively.Based on the powered flight trajectory of launch vehicle,the effects of attitude maneuvers on the INS transfer alignment in these two coordinates are analyzed through typical flight simulations.Theoretical models and simulation analyses show that the transfer alignments in the two coordinates have obvious differences in terms of principle,model and system characteristics.The effects of typical alignment schemes are presented,which show that the match scheme of "angular velocity + acceleration" in launch-point inertial coordinate is an effective method for realizing rapid and accurate initialization of sub-INS.

Single-rotating inertial navigation system with ring laser gyroscope

Abstract: High precision inertial navigation system is the base of integrated performance in shipsIn order to improve the performance of the inertial navigation system,a method to rotate the inertial measurement unit is developedThe hardware of the system is introduced,which mainly includes the basic configuration,the performance of ring laser gyroscope and accelerometer,and the diagram of navigation computerThe scheme of the alignment and the temperature compensation are describedThe static tests and outdoor vehicle tests are performedThe results show that the peak position errors of the four times static navigation tests for 10-day cycle are less than 1 n mile within 5 days,and 2 n mile within 10 daysThe peak position errors of the outdoor vehicle tests are less than 14 n mile within 77 h,and 25 n mile within 15 days

Adaptive SVD-UKF algorithm and application to integrated navigation

Abstract: This paper puts forward a new unscented Kalman filtering(UKF) algorithm.To control the effects of dynamic model errors on the solution of navigation parameters,the ratio of dynamic model information and observation data are made into equilibrium by an adaptive factor.Singular value decomposition(SVD) of matrix is adopted to substitute for the iteration of covariance matrix and improve the numerical stability of the covariance matrix.The simulation is made which applies the proposed algorithm into an integrated navigation system and compares it with adaptive Kalman filtering algorithm and adaptive UKF algorithm respectively.The results show that the new algorithm has higher robustness,and can effectively improve the filter performance and position accuracy of the integrated system.

Digital double-closed-loop drive control method for silicon microgyroscope

Abstract: A digital double-closed-loop drive control circuit was designed and realized based on FPGA to improve the performance of silicon microgyroscope.The principles of the drive control scheme were presented,in which phase control loop was used to track drive mode resonant frequency,and direct current control loop was used to stabilize the amplitude of vibration displacement.The two closed-loops were designed based on FPGA assisting ADC and DAC.By means of frequency sweeping and direct current scanning test,the conversion coefficients from phase error to frequency adjustment in phase control loop and that from amplitude error to direct current adjustment in direct current control loop were obtained.Using Xilinx ISE and EDK software,the logics for devices interfaces,parameters solution,digital filters,signal generation and the programs for data access,control algorithms,sweeping test,serial communication were designed respectively.Experiments show that the relative tracking error of drive mode resonant frequency is up to an order of 10-6 and amplitude stability up to an order of 10-4 after the system is stable.

Accelerated storage life evaluation of FOG based on drift Brownian movement

Abstract: The storage life of FOG(Fiber Optic Gyros) is an important index for its military application.Aiming at this issue,the accelerated storage degradation testing is implemented to test the FOG for its long life and high reliability.The evaluation based on drift Brownian movement is utilized to evaluate the storage reliability and storage life of FOG.Based on the failure mode effect and criticality analysis(FMECA) results of FOG,an accelerated model is established.Then,the reliability evaluation model is generated combined with linear drift Brownian movement.Using the degradation data of FOG acceleration storage,the storage life of FOG is evaluated.The evaluated results are reasonable,and the feasibility of the method is validated.

Calibration of nonlinear model parameters of high-precise accelerometer in RLG-SINS

Abstract: An orthogonal coordinate of IMU,bounded by laser gyro axes,is established in order to reduce the measure error of accelerometer caused by inner-absorber deformation in SINS.Considering the obvious nonlinear error of high-precision accelerometer which bias stability is better than 5 × 10 ?6g,a nonlinear measure model of accelerometer is proposed.Relying on the three-axis turntable,with the accuracy of 5 arc-seconds in the angle orientation,an idea of stepwise LSM identification and the linearization of nonlinear model,are introduced.At the first step,the model square coefficient is calculated when the turntable is in the orthogonal multi-position.And then,the model cross-coupling coefficient is identified,depending on the declining multi-position of the turntable.The test results illustrate that the standard deviation of gravity measure error by accelerometer’s nonlinear model is 9.38% of the linear model in the first stage,with the maximal standard deviation of measure error by square coefficient in the three tests,which is 8.53 × 10 ?7g.And when the turntable is in the declining multi-position,the standard deviation of gravity measure error based on the linear model of accelerometer is reduced to 31.41% in the nonlinear case.At the same time,the maximal standard deviation of measure error by cross-coupling coefficient of three tests is 1.14 × 10 ?6g.According to the above facts,the exact calibration of high-precision accelerometer has been achieved.

Suppression for light source intensity noise in high-precision FOG

Abstract: The light source intensity noise in the superfluorescent erbium-doped fiber source is a major factor that affects the angle random walk(ARW) of FOG.To reduce the ARW and improve the precision of FOG,a method for reducing the light source intensity noise is put forward,i.e.the digital subtraction in a field programmable gate array(FPGA),which is based on the correlation between the two parts of the coupler.The output data of FOG was analyzed by Allan variance without the digital subtraction and with the digital subtraction respectively.The results indicate that 33% reduction is demonstrated in the ARW of FOG.This method is simple to implement,high reliable,and easy to maintain.

Improved calibration scheme for high precision IMUs based on turntable error analysis

Abstract: The turntable's error model for high-precision inertial measurement units(IMUs) is constructed based on attitude transformation quaternionFirst,the propagation of the turntable's errors in typical IMU calibration is analyzedThen,based on the turntable error analysis,an improved calibration scheme for high precision IMUs is presented,which can effectively reduce the turntable's errors and increase the calibration accuracySimulation and test results of a laser gyro strapdown inertial navigation system show that the improved calibration scheme can increase the calibration accuracy and improve the navigation performance

Dynamic sliding-mode control with backstepping for stabilization loop of inertial platform

Abstract: A dynamic sliding-mode control (DSMC) with backstepping is proposed for the stabilization loop of inertial platform (SLOIP) with mismatched uncertain nonlinear disturbance.An equivalent model,which is composed of a linear model and an uncertain nonlinear function,is built to approximately represent the dynamics of SLOIP.Then,the DSMC with an asymptotical sliding surface is designed based on the backstepping method for the trajectory tracking control of SLOIP.Based on Lyapunov stability theory,the analysis on the designed controller is made,which shows that the controller can not only ensure the stability of the closed-loop system,but also adjust the convergence rate of tracking error by properly choosing the control parameter values.The simulations verify that,compared with PID control,the tracking precision and the robustness of the system are improved by the proposed control method.

Temperature compensation of MEMS gyroscope based on grey model and RBF neural network

Abstract: The zero bias of MEMS gyroscope exhibits nonlinear change with varying temperature and contains significant stochastic errorIn view that traditional polynomial method could not accurately establish the relationship between the temperature and the zero bias,this paper puts forward a hybrid model based on grey model theory and RBF neural networkFirst,it pre-processes the gyro output using the grey model to reduce the noiseThen it uses the processed sample data to train the RBF network,so the training errors are reduced by one magnitude within the same training timesThe verification experiments indicate that compared with traditional polynomial model and untreated RBF neural network,the compensated gyro zero bias error is reduced by one order of magnitude and 2/3 respectively

North seeker using single axis FOG

Abstract: The FOG north-seeker adopts combined technical scheme with a FOG and double axis accelerometers.The constant drifts of FOG and the bias of accelerometers are eliminated by using two-position north seeking scheme.By adding a sampling position which contra-rotates 90° from the initial position of FOG axis,all-azimuth north-seeking is realized.In order to eliminate the effect of base disturbance on the precision of north seeker on a stationary carrier,a mixed iterative algorithm based on robust estimation is put forward,which is based on high breakdown point initial value and assisted by IGG Ⅲ scheme.Its structure is simple and its function is easily implemented,so the performance is stable.The tests show that the north seeking accuracy is less than 3' in 5 min.

Method of image overlay on radar and electronic chart

Abstract: Radar and electronic chart are important navigational equipments for vessel traffic.A method of image overlay on radar and electronic chart is proposed to improve the sailing security.The extracted radar image is processed by geometric transformation according to the local position and True North of the ship.Refer to the scanning radius of the radar,the range of electronic chart is adjusted by mercator projection transformation,and then the scale of electronic chart is changed to get the image of radar and electronic chart matching.Using electronic chart as background,radar image is overlaid in pixel level.The simulation results show that the method of image overlay on radar and electronic chart is effective for the sailing security.The coastline of electronic chart and radar image are matched well.Radar targets can be displayed in real time.The monitoring capability on ship's surrounding environment is enhanced.

Adaptive fuzzy Kalman filter based on INS/GPS integrated navigation system

Abstract: This paper presents a novel GPS/INS integrated navigation algorithm based on Fuzzy Adaptive Kalman FilteringThe method is mainly used in GPS/INS integrated navigation system to deal with time varied statistic of measurement noise in different working conditionsBy monitoring the covariance between abstract residual and actual residual,the algorithm recursively modifies the gain coefficients of the filter so as to adaptively control the Kalman filter,and finally the optimal estimation is achievedThe experimentation results of the INS/GPS integrated navigation system indicate that the algorithm is effective and practical

Initial alignment method for rotational strapdown inertial navigation system based on strong tracking filter

Abstract: The rotational strapdown inertial navigation system(RSINS) has improved its conventional system architecture,i.e.,the gyros and accelerometers are placed on a rotating base,thus their non-stochastic errors could be eliminated by the integral calculation of navigation algorithm.Considering its structure features,a novel initial alignment method based on strong tracking filtering algorithm is presented which can rapidly estimate the platform misalignment.The mathematical model of the system errors is established,and the state equations and observation equations of strong tracking filter are derived,and the verifications by digital simulation are given.An inertial measurement unit(IMU) is constructed based on a certain type of fiber-optical gyro and a certain type of MEMS accelerator.Using the IMU,semi-physical simulations are conducted on a high-precision rotary table using the real data measured by the data acquisition system to verify the performance of the proposed method.The simulation results show that,compared with SINS's conventional initial alignment method,the proposed method has higher initial alignment performance for medium and low precision rotating SINS,and is valuable for engineering application.

Optimal design of accelerometer test on precision centrifuge

Abstract: A modified D-optimal design method for accelerometer test on precision centrifuge is presented in this paper.First,the measurement noise characteristics of accelerometers in centrifuge test is analyzed,and based on this,it is pointed out that the traditional design method i.e.the saturated D-optimal design method,has the problem of engineering applicability.Second,considering the relationship between experiment cost and precision,a modified experiment design scheme is given to improve the applicability of saturated D-optimal experimental design.This scheme utilizes the spectral points got by saturated D-optimal method as the basic spectral points,and uniformly inserts some points into the basic spectral points to decrease the effects of acceleration setting errors,and then regulates the measurement allocation of basic spectral points and inserted spectral points by the weights which are selected according to practical noise components.The simulation results show that this design method,which synthesizes the merits of the saturation D-optimal design method and the uniform design method,can give more reasonable test plan for accelerometers on precision centrifuge.

Low-cost GPS/INS integrated navigation algorithm in land vehicle system considering attitude update

Abstract: The instrument errors in low cost INS can significantly degrade the navigation precision.In this paper,an attitude update algorithm for GPS/INS integrated navigation system on land vehicle is put forward.First,two kinds of attitude observation equations are given based on GPS/INS loose navigation.Then the principle of yaw angle determined by GPS velocity is introduced and the pitch and roll angles of low-cost INS in land vehicle are analyzed.It is suggested that the pitch and roll angles should be kept constant when the errors caused by instrument errors are bigger than themselves.By the actual data calculation,the precision of yaw angle determined by GPS velocity is obtained,and it is shown that,compared with the Kalman filtering based on position and velocity,the new algorithm significantly improves the navigation accuracy.

Application of ESO and TD to outer field calibration of laser gyro SINS

Abstract: The calibration problem for estimating 9 error parameters of the strap-down inertial navigation system(SINS) under outer field conditions is studied.When only the information of velocity errors and position errors can be available in the outer field,the minimum position number,which should be satisfied in order to estimate the 9 parameters with high precision,is obtained based on the observability analysis.A novel calibration method is proposed which can estimate the 9 parameters through extracting the derivatives of the velocity error signals via the extended state observer(ESO) and the tracking differentiator(TD).A feasible multi-position calibration design is tested by simulation.The result shows that this method can quickly calibrate the 9 parameters with high accuracy,and it is easy to be implemented in the outer field.

Application of unscented Kalman filter in identification of INS error parameters based on centrifuge test

Abstract: In order to identify the error parameters of inertial navigation platform in the centrifuge testing,a non-linear model of INS for the identification with a direct method is established.According to the actual system model,the standard unscented Kalman filter(UKF) algorithm is simplified and improved.Compared with the standard UKF,the improved algorithm has the same filtering precision,simpler configuration and lower calculation load.An extended Kalman filter(EKF) algorithm and the improved UKF algorithm are applied respectively to identify the error parameters of INS based on centrifuge test.The simulation results demonstrate that the improved UKF algorithm is more precise in INS error parameter identification and easier to implement than EKF algorithm.

Geomagnetic matching algorithms based on affine model

Abstract: To improve the efficiency and precision of undersea vehicles,a two-level geomagnetic matching(rough and fine) algorithm using affine model transposition is put forward based on the analysis of the INS(inertial navigation system) error models of underwater vehicleFirst,it uses the correlation matching method,which is based on contour constraint,to eliminate the initial position error of INSThen,it uses an affine model to circumgyrate and zoom the tracks obtained from correlation matching resultsFinally,through scanning correlation parameters,the accurate matching process is realizedExperiments show that the algorithm not only meets the real time requirement,but also has the matching precision of better than one grid

High-precision north determining scheme based on rotation-modulation technology

Abstract: With enough position sampling data,the method of multiposition north seeking can effectively reduce the gyro drift,gyro scale factor error,etc.,and improve the accuracy of the north seeking.But it is difficult to realize the multiposition sampling in engineering within the limited time.To solve this problem,a north seeker system based on spin modulation is developed.Based on the study of its principle,the influences of the system’s main error sources on the north-finding results are studied.The prototype experiment results show that the north-seeking accuracy of the prototype is superior to 30″(1δ) in 4 min,and under the same conditions of gyro accuracy,this system significantly improve the north seeking accuracy compared to that of traditional ones.

Improved parameter identification method for SINS initial alignment

Abstract: The existing defects in parameter identification measurement model in traditional parameter identification method for the initial alignment of strap-down inertial navigation systems(SINS) reduce the alignment convergence speed and accuracy,especially under linear moving disturbance environment.In this paper,an improved parameter identification model is presented.It takes the average effect of linear disturbance into the identification model to improve the alignment convergence speed and accuracy.Moreover,an identification model of double integral of specific force is derived and adopted which significantly suppress the linear disturbance.Simulation results show that the inherent errors in alignment algorithm could be eliminated by the proposed method,and smoother estimated effects for misalignments are obtained.

Fusion algorithm of angular velocity weighted averages for GFSINS based on dynamically allocating weights

Abstract: In view of low precision of single angular velocity algorithm,an optimal weighted average method is ap-plied to the calculation of GFSINS angular velocity.Since the variance of angular velocity errors for each algorithm can't be accurately obtained in the practical application,a weighted fusion algorithm is given which estimates the variance in real time and allocating weights dynamically based on optimal weight allocation principle.Integral algo-rithm,extraction algorithm,differential algorithm and lognormal algorithm are effectively fused,and the simulation is made.The results show that fusion precision can be further improved even if with the integral algorithm.Moreover,the validity of optimal weighted average method is proved.After fusion,the angular velocity precision is one times higher than that by logarithmic method.

Systematic calibration method for SINS with low-precision two-axis turntable

Abstract: In order to reduce the requirement for turntable precision in SINS calibration,a ten-position calibration method for SINS using low precision two-axis turntable is presented.First,by choosing a suitable IMU frame,the error models of accelerometers and gyros are established respectively.Based on the models,ten positions used in calibration are reasonably arranged on two-axis turntable.Then by taking the navigation errors in SINS rolling as observations,the overall twenty-four error parameters of SINS are identified,including the nonlinear terms of scale factor error.The mathematic simulation and physical experiment both verify that the method can identify all the error coefficients of SINS on low-precision two-axis turntable,and the accuracy of this method is equivalent to that of the classical calibration on precision turntable.In addition,this method is rapid,simple and feasible.

Design of low cost GPS/DR fault-tolerant integrated navigation system

Abstract: GPS signal is especially susceptible to being obstructed by dense trees or high buildings.Meanwhile the inertial devices of micro electro mechanical system(MEMS) have large random drifts,and its performance changes sharply with temperature.So the low cost GPS/DR system using ordinary Kalman filter(KF) to fuse GPS and MEMS inertial devices can hardly meet the accuracy and fault tolerant requirements.To solve these problems,a fault tolerant UKF(Unscented Kalman filter)/KF federated Kalman filter algorithm is designed,and the random drift of the MEMS inertial devices is restrained by heuristic drift reduction(HDR) method.The simulation results show that the accuracy and fault tolerant ability of the GPS/DR system are both improved,and the system can remain high positioning accuracy within relatively long time when GPS signal is lost.