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2011 Vol. 37, No. 1

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Analysis on three dimensional water droplets impingement characteristics of engine inlet
Shen Xiaobin, Lin Guiping, Yang Shenghua
2011, 37(1): 1-5.
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Droplets impingement characteristics of a certain 3D engine inlet were analyzed using an Eulerian method with numerical diffusion. Calculation of 3D complex body’s local droplet collection efficiency was conducted in the compressible flow field. With numerical diffusion, the problems of singularity and divergence were solved. Cases of different mass flow rates were calculated with and without cowling. Results show that mass flow rate influents on the impinging area and amount around engine inlet lip. The bigger is engine mass flow rate, the larger is the maximum local droplet collection efficiency. The results also show that the influence of cowling on this engine-s impingement characteristics is very small in these cases.
Analysis on gas film stability performance of gas film seal damper
Hong Jie, Wang Hong, Ma Yanhong
2011, 37(1): 6-9,35.
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In order to solve the problem of gas dynamic seal and vibration of rotor system in high-speed rotating machinery, a novel gas film seal damper (GFSD) with flexible metal rubber ring was brought forward. The function of gas film between the stator and rotor is seal and damping while the high elasticity ring can control the dynamic property of gas film. The quasi-static method was employed to describe the fluid-solid coupling among rotor, gas film and metal rubber ring. Based on finite difference method, the gas film pressure field was analyzed, and the effects of the structural and working parameters on the stability performance of GFSD, including gas film force, leakage and friction torque, were discussed. The results show that the flexible ring can improve gas film pressure field effectively. The proper range of structural parameters is defined by the actual working conditions. With the given working parameters, a better stability property will obtain with the ratio of width and diameter 1.5, the seal clearance 0.05mm and the flexible coefficient around 2.
Effects of off-center location on aircraft attitude during catapult launch
Yu Hao, Nie Hong
2011, 37(1): 10-14.
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Owing to the deck motion and some other factors, the aircraft often has off-center distance with the catapult orbit. To study with this phenomenon, considering the deck motion, landing gear cushion and flexible tires, a six-degree-of-freedom mathematic model of carrier-based aircraft off-center catapult launch was established. The aircraft attitude during catapult taxing affected by the off-center distance with typical deck motion was studied. From the off-center catapult launch calculation, three important conclusions were obtained.The yaw movement are affected clearly by the initial off-center distance and its amplitude increases with the increase of the initial off-center distance.The attenuation of the yaw movement is clearly during catapult taxing and the launch bar side bending moment increases with the increase of the initial off-center distance. The results provide theoretical foundation for carrier-based aircraft design.
Bleeding impact on performance of transonic axial compressor
Zhao Bin, Li Shaobin, Zhou Sheng
2011, 37(1): 15-20.
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By analyzing the transonic single-stage compressors NASA Stage35, multiple bleeding plans were presented according to the physical phenomena of the flow in rotor and stator passage. Combined with experimental results, compressor flow field with and without air bleeding were compared to study the impact of the rotor casing bleeding position and the stator casing bleeding amount on the compressor flow field and performance. The results show that rotor casing bleeding can inhibit the development of tip leakage flow in the passage circumferential, reduce the flow loss of the tip region and enhance the compressor performance. The impact mechanisms on the tip flow field vary as the bleeding positions and structures change. Stator casing bleeding can cut the flow loss and improve the compressor efficiency.
CE/SE method applied to flows around 2D airfoil
Cui Shuxin, Han Yuqi, Gao Ge
2011, 37(1): 21-24.
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A numerical scheme for solving Euler equations was conducted to investigate inviscid flows around 2D airfoil according to space-time conservation element and solution element (CE/SE) method. Courant number insensitive scheme (CNIS) used to avoid the contaminations of numerical dissipation induced by very small Courant number, improved the accuracy combining with local time-stepping(LTS) method that canceled the disparity in Courant number at non-uniform meshes. Two dimensional numerical simulations for NACA0012 airfoil were implemented. The results show that it is in agreement with the published data by AGARD, which will provide sufficient preparations for the application of CE/SE method to airfoil at more fields.
Method of ground clutter simulation in range gate signal level for airborne bistatic radar
Li Yingchun, Li Jingwen
2011, 37(1): 25-30.
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Ground clutter simulation of bistatic radar is complex due to the variety of geometry configuration. The method of clutter scatterer division in monostatic radar can be applied to bistatic radar, while it is inconvenient for clutter analysis in specific range gates. One clutter simulation approach in range gate signal lever for airborne bistatic was proposed based on the comparison between ground equidistance traces of bistatic and monostatic radar. The equidistance ellipse rings were divided with two-way distance resolution in range direction, the expression of ground ellipse was deduced, and the analytic resolutions of scatterers were presented. In azimuth direction the clutter cell grids were dispersed by introducing intermediate variable guaranteeing the Doppler resolution, and the computing processes of unknown parameters used in clutter simulation were presented. The approach can complete not only the simulation of clutter spectrum for overall area observed, but also the computation of the clutter echoes in one or some special range gates. Simulation results prove the validity of the method.
Partition modeling and design in integrated avionics
Li Xinying, Xiong Huagang
2011, 37(1): 31-35.
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With the development of integrated modular avionics, partition management has become a necessary technology. To solve the partition management problem under safety critical system constraint, through studying ARINC653 criterion, hierarchical partition architecture model was determined which implement partitioning between applications of different safety critical levels. To guarantee timing constraints and predictability of avionics, a two-level partition schedule model was proposed in which the operation system adopts round-robin scheduling strategy and each individual partition adopts rate monotonic priority scheduling strategy. In addition, for the schedulable analysis problem of partition tasks, on the premise that fully guarantee real time characteristics of integrated modular avionics systems, a design method for partition critical parameters was developed. The least upper bounds of the system schedulable utilization for the method was derived and formally proved. Computer simulation results indicate this approach can be used to admit much more systems load, while guarantee real time properties.
Numerical simulation of ice accretion on multiple element airfoil and prediction on anti-ice situation
Zhong Guo, Cao Yihua
2011, 37(1): 36-40.
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A modified model of the mass and heat transfer on ice surface was proposed based on the classical Messinger model to study the prediction of ice accretion on aircraft. Another model of the prediction of ice accretion on multiple element airfoil was founded via introducing the interpolation calculation of airflow field around the multiple element airfoil. Considering the equivalent thermal power from anti-ice system, a method of the prediction of ice accretion on anti-ice situation was proposed. The agreement between the result of numerical simulation and the experimental data indicates that the models proposed are feasible and effective, and they can lay the foundation of the research about the dynamics in the icing condition and the design of anti/de-ice system.
Airfoil robust design with uncertainty parameters
Liu Yang, Qiu Zhiping
2011, 37(1): 41-44,53.
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A robust design optimization of 2D airfoil with uncertainty of inlet Mach number was presented. Based on NACA0012, a series of geometry as well as boundary parameters were introduced. Three optimization methods, including single-point method, multi-point method as well as robust method,were discussed. Airfoil sample points were obtained using uniform design theory for the response surface training of Kriging model. Consequently the corresponding parameters of the airfoil were identified for optimal robust design with genetic algorithm. The influence of geometry parameters perturbation on the aerodynamic performance was discussed by applying interval analysis method. Compared with the traditional genetic algorithm, the optimization process presented has advantage in terms of time consumption.
Method for estimating largest Lyapunov exponent in non-smooth multibody systems
Fu Li, Wang Qi
2011, 37(1): 45-48.
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According to the theories of both non-smooth mechanics and non-linear dynamics, a numerical method for estimating the largest Lyapunov exponent in non-smooth multi-body systems with unilateral constraints was presented. Lagrange equation of the first kind was applied to derive the structure-varying dynamic equations of the systems and the scheme for linear complementarity problem(LCP) was used to detect non-smooth events, such as stick-slip transition, detachment,collision andsoon.Chaos synchronization method was applied to estimate the largest Lyapunov exponent. The algorithm of bisection and the algorithm of coupling parameter modulation were used to increase the speed of calculation.The numerical results obtained from two examples indicate that the method is effective.
Convective heat transfer analysis of anti-icing surface
Song Xin, Lin Guiping, Bu Xueqin
2011, 37(1): 49-53.
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An integral analysis of momentum and thermal boundary-layers was used to determine the convective heat transfer coefficient on two-dimensional airfoils with thermal anti-ice system. The objective are to implement two different boundary-layer models: one assumed isothermal surface with prensence of a abrupt laminar-turbulent transition, while the other considered the boundary-layers over a non-isothermal surface with a smooth laminar-turbulent transition region. The onset and length of laminar-turbulent transition was estimated by classic empirical correlations. The surface equilibrium temperature distribution was predicted by an integrated airoil leading-edge interior-exterior thermodynamic analysis, compared to the literature and experimental data. The results indicate a validity of using boundary-layer anaylysis with smooth laminar-turbulent transition in predicting anti-icing convective heat transfer and surface temperature, but the simulation shows that surrounding static pressure has a large effect on the results accuracy.
Modeling and attitude control of aircraft with variations in mass or center of gravity
Yang Xiaoke, Yang Lingyu, Zhang Jing, Shen Gongzhang
2011, 37(1): 54-57,62.
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To solve the attitude control problem of aircraft with variations in mass and center of gravity (CG), a general model, including the dynamics and mass/CG variation properties, for such aircraft was established with the variations converted to disturbance forces and moments. This model was able to reveal the dynamic couplings between the CG shifts and aircraft motions, and the induced disturbances. For the attitude control of such aircraft, with variations in mass and CG treated as unknown disturbance inputs, an observation and compensation framework was proposed. The longitudinal attitude controller was then designed within this framework based on the proportional-integral observer (PIO) which estimates the disturbance force and moment inputs caused by mass and CG variations. The PIO compensation command was added to the regular autopilot. In the example of heavy load airdrop on cargo aircrafts, computer simulation demonstrated the proposed model could accurately reflect the aircraft-s dynamic responses in every stage of mass/CG variations, and pitch attitude response was greatly improved compared with controller without PIO compensation command and met precise attitude control requirements
Power aware scheduling of resource-constraint embedded mechatronic control systems
Li Feng, Wang Tianmiao, Wei Hongxing
2011, 37(1): 58-62.
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To solve energy constraint of embedded mechatronic control systems(EMCS), an energy management method based on feedback scheduling and power aware was proposed. The static optimization model of EMCS was discussed. A joint optimization target based on the control cost and the system energy consumption was proposed, and the optimal solution was given. In dynamic scheduling, the overhead of static optimization is very high and difficult to realize, so intelligent computing methods were used to approximate the optimal solution. Scheduling overhead and approximation accuracy of four intelligent computing methods were compared, and wavelet neural network was used to approach optimal results. Results of simulations show that the energy consumption on the base of maintaining control performance was reduced effectively by the proposed method.
Predictive guidance method for the reentry vehicles based on fuzzy logic
Wang Junbo, Qu Xin, Ren Zhang
2011, 37(1): 63-66,85.
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A novel predictive guidance was presented for the reentry vehicles based on the fuzzy logic system, according to the requirement of real-time capability. The relation of reentry vehicles- altitude, range and flight path angle was analysed firstly. The system of fuzzy logic was designed with altitude and deviation on target as system inputs and the angular rate of flight path angle as system output. The system took advantage of the experts- experiences to construct the fuzzy rules. Then a novel predictive guidance method was devised following the fuzzy logic which was used for guidance command generation. The method avoids massive iteration computation of general predictive guidance when calculating the angular rate of flight path angle revision command and decreases calculating time of predictive guidance to a satisfactory level effectively. The simulation results indicate the strong anti-interference capacity, high guidance precision and great practical value in engineering of this new predictive guidance method.
Estimation of vehicle speed based on Kalman filter and ABS control inputs
Ding Nenggen, Li Danhua, Yu Guizhen
2011, 37(1): 67-71.
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Based on the existing algorithms, an algorithm of vehicle speeds for anti-lock braking system (ABS) was investigated using parameter adaptive Kalman filter and ABS control inputs. With the four wheel speeds as inputs, the vehicle braking deceleration was estimated utilizing ABS control inputs. Then the speeds on both left and right sides were estimated independently using information of wheel speeds and deceleration. According to different slip conditions, the covariances were tuned using the parameter adaptive Kalman filter. At last, the proposed algorithm was evaluated using real test data of ABS braking, and results show that the estimated speeds are reasonable under various road conditions.
Simulation and analysis of brushless DC motor double closed-loop control strategy
Huang Zhi, Guo Hong, Wang Dayu, Xu Jinquan
2011, 37(1): 72-75.
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Load disturbance exists in direct drive valve(DDV) servo system. Meanwhile conventional triplex closed-loop control structure cannot satisfy DDV servo system in rapidity. Therefore double closed-loop control structure was adopted. Position and velocity double closed-loop system was compared with position and current double closed-loop system. The optimal proportion integral coefficients could be obtained through the method of frequency domain analysis. The simulation results show that double closed-loop control systems perform well in static and dynamic operation. Meanwhile the influence of load disturbance can be reduced effectively. When the system has a small damping coefficient, position and velocity double closed-loop system performs better in load adaptability. Position and current double closed-loop system performs better in rapidity. The comparison between the simulation results and theoretical analysis shows a good agreement.
Self-adaptive filtering algorithm for scattered points
Sun Dianzhu, Zhu Changzhi, Fan Zhixian, Li Yanrui
2011, 37(1): 76-80.
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A self-adaptive filtering algorithm for scattered points was proposed. The node splitting algorithm and the clustering algorithm of R*-tree were improved and the spacial index structure of triangular mesh model was established based on the improved R*-tree; The local surface reference data was obtained according to data nodes- distributing of the spacial index structure; The filtering weight was computed by self-adjusting figure feature of 2-D Gauss distributing according to its local surface reference data; The weight value of local surface reference data to originality surface data was computed, and the coordinate of scattered points was computed according to this weight value; The self-adaptive filtering for scattered points was realized with the method of weighted mean. It proved that this algorithm can improve the efficiency of filtering and reduce the random error of the scattered points on the basis of the accurate reservation of surface characteristic.
Equipments support footprint forecast model based on support activity flow
Qiu Yanlin, Zhang Wenjin
2011, 37(1): 81-85.
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In order to resolve the problems encountered in the process of forecasting the equipments support footprint during the design and development phase, including the difficulty to collect the input data of the forecast models and their imprecise and unauthentic output results, an equipments support footprint forecast model was established based on support activity flow described by functional flow diagrams, which used the data of support system modeling and the results of the equipment-s supportability analysis as input. A bottom-up approach to sum the total quantity of the resources demanded by the support activities with logic relations in the same level of the functional flow diagrams was presented, which considered the characteristics of support resources being consumed or occupied in equipment-s operational and maintenance activities. The equipments support footprint was calculated on the basis of the weight and volume of the support resources and their number allocated in the support site which was calculated by the former approach. The proposed model was demonstrated via a practical case of aircraft, which proved that the model and analysis mythology is effective theory for equipment deployment analysis.
Design and implementation of personalized desktop for enterprise portal
Pu Juhua, Liu Wei, Xiong Zhang
2011, 37(1): 86-90.
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Personalized desktop for enterprise portal(PD4EP) was presented, which provided personalized customization to every personal user. PD4EP classifies portal channels to some categories and constrains the personalization for each category. Thus personalization for portal channels belonging to the same category can be uniformed and users can customize multiple portal channels in batch at the same time. The modular system structure was used in PD4EP to separate specific enterprise portal business from portal resources, which reduced the coupling between portal desktop system and other portal components while increased the generality of the system. With above characteristics, PD4EP can be used to design a new enterprise portal desktop system, and to expand an existing enterprise portal desktop by plug-in personalized portal channel. Personalization operation processes in PD4EP were based on inversion of control, which enhanced the compatibility between portal desktop system and portal channels which may be developed by different developers.
Reliability testing and evaluation technology for LAN FTP applications
Chen Yang, Huang Ning, Kang Rui, Li Ruiying
2011, 37(1): 91-94,122.
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The concept of computer network application reliability was introduced, and it focuses on the different reliabilities caused by different applications. On the basis of the index evaluation method, the testing procedure of local area network(LAN) file transfer protocol(FTP) application reliability was discussed and a novel testing and evaluation method was proposed. Meanwhile, an LAN in a laboratory was tested and evaluated by the method mentioned above. In this case, to solve those problems in the testing process, a Windows batch script to generate FTP packets was programmed as the LAN application traffic generator; a testing data collection method was studied on based on Sniffer Pro. And also, the testing steps were given and the reliability evaluation results were attained. In the testing case, the collected data matches with the network state. Therefrom, the proposed testing and evaluation technology is verified and can be seen as a reference provided for other application reliability study.
Impact energy absorption characteristics of single-walled carbon nanotubes
Leng Dingxin, Sun Lingyu, Lin Yi
2011, 37(1): 95-100.
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The excellent mechanics characteristics of carbon nanotubes make them potentially applicated in energy absorption, however, it is still difficult to be verified by nano-scale experiments. By integrating the principle of molecular structural mechanics into the nano-scale finite element method, the fracture process of single-walled carbon nanotubes(SWCNTs)under axial impact loads was simulated based on the principle of impact dynamics. The parametric structural model of SWCNTs was built by APDL language in ANSYS software. Meanwhile, the constitutive equation of C-C bond was obtained by the modified Morse potential function. According to the failure strain criterion, the energy absorption capability of SWCNTs with different diameter, length and chiral was investigated. The proposed simulation method can effectively predict the locations and directions of fracture in SWCNTs, and the growth process of rupture could also be visualized dynamically. It is demonstrated that the specific energy absorption of SWCNTs is much higher than that of similar tubes manufactured by other materials. In addition, the energy absorption of zigzag SWCNTs is higher than that of the armchair SWCNTs.
Generalized nonlinear strength and general mobilized plane
Wang Naidong, Yao Yangping
2011, 37(1): 101-105.
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Corresponding to the extended Mises criterion, the stress ratio of the shear stress to the normal stress on the octahedral plane is a constant. Corresponding to the spatially mobilized plane (SMP)criterion, the stress ratio on the SMP is a constant. The generalized nonlinear strength theory (GNST) covers most of nonlinear failure criteria. Corresponding to the GNST, there should be a plane in the physical space on which the stress ratio is a constant.The conception of general mobilized planes (GMP)was proposed, which are between the octahedral plane and the SMP. The stress ratio on the GMP is a constant corresponding to the GNST. The expression of the stress ratio on the GMP and the failure surface in the principal stress space were also given. It can be concluded from the detailed analysis and comparison that the GMP consists with the GNST for describing the failure of materials.
State recognition of tool wear based on wavelet neural network
Nie Peng, Chen Xin, Xu Tao, Sun Baolin
2011, 37(1): 106-109.
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In connection with the processing characteristics of aviation parts, acoustic emission(AE) signals of tool which in different wear state were acquired. Time-frequency analysis and wavelet transform were utilized on the AE signals. Fast fourier transform and db8 wavelet decomposition were used to extract the amplitude root-mean-square value and the main band energy value which were considered as eigenvectors of AE signals. Then the eigenvectors were normalized and taken as input vector for the training of wavelet neural network. Parameter adjustment algorithm was applied to add momentum term to weights and threshold for amendment in the wavelet neural network. The results indicate that the frequency range of tool AE signals which sensitive to different wear states is between 10-150kHz. The error between the trained wavelet neural network actual output and expect output is less than 0.03. Different tool wear states can be recognized correctly and effectively by this method.
Fast nonsingular terminal sliding mode control based on multi-slide-mode
Zhao Xia, Jiang Yuxian, Wu Yunjie, Zhou Yinqiang
2011, 37(1): 110-113.
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A fast nonsingular terminal sliding mode (FNTSM) control is proposed to realize the global fast convergence of nonsingular terminal sliding mode control based on the concept of multi-slide-mode(MSM). The MSM has several sliding modes by designing piecewise switching function. According to the concept of MSM,the switching function of FNTSM is connected by the switching function of linear sliding mode and nonsingular terminal sliding mode. If the system state is far away from the equilibrium,the system runs on linear sliding mode. If the system state is near to the equilibrium,the system runs on nonsingular terminal sliding mode. A switching control law is designed to guarantee the reaching time and sliding time are finite. The simulation show the FNTSM control is faster than nonsingular terminal sliding mode control and linear sliding mode control.
Short-period forecasting algorithm for air pollution concentration in road tunnel with longitudinal ventilation
Chen Jiantao, Li Yunhua, Liu Dongxiao
2011, 37(1): 114-118.
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The computation of road tunnel air pollution model often adopted finite volume method, and was time-consuming, strenuous, difficult to be used in dynamical ventilation control system of road tunnel. Pollution concentration distribution in road tunnels was near linear along tunnel length. According to this characteristic, a new linear iteration formula was deduced from tunnel ventilation pollution model described by partial differential equation of second order. The practical methods to compute new variables in the formula were proposed. And the physical process denoted by the formula was illustrated. Then the formula was validated with detected CO concentrations from Qingling tunnel of Xihan highway, and it is found that the formula can cursorily offline forecast CO concentration in road tunnel outlets. To improve forecast precision, the previous formula was amended using detected data. And another predictive method with observation error correction was put forward and validated with the detected data. The results show this method can more accurately online forecast CO concentration in the tunnel outlets.
Preparation of Al-Co codeposition coating on surface of Ni-based alloy
Yuan Bifei, Lu Guiwu
2011, 37(1): 119-122.
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A novel Ni-Al-Co coating was developed through pack cementation for protection of superalloys. Surface and cross-sectional observations of the coated specimens were preformed on a scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). X-ray diffraction (XRD) was used in order to detect the phases formed. The results show that the developed Ni-Al-Co coating, which is mainly composed of AlNi, AlCo and Al-Cr intermetallics, shows monolayer structure. The contents of Al and Co are obviously higher than that in the substrate. Furthermore, an interdiffusion layer has been developed between the Ni-Al-Co coating and the substrate. The interdiffusion layer shows good adherence on the substrate because no cracks and spalling was detected at the interface between the interdiffusion layer and the substrate. The formation of the interdiffusion layer may be induced by the precipitation of the elements of Cr,W,Mo,Ti during the pack cementation.
Novel calibration method for accelerometers of in-field use
Mao Youze, Zhang Hai
2011, 37(1): 123-126.
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To solve the problem that parameters of accelerometers varied with time, a calibration method for accelerometers of in-field use was proposed. Resources in inertial navigation system(INS) was used rather than traditional calibration equipment, such as a precise turntable in this method.There was no need to unload INS from carrier in the calibration. The initial alignment obtained accurate gesture information and the Earth-s gravity was used as calibration standard. Non-linear optimization strategy was introduced to identify the zero bias,considering the non-linear property of the error model.Then the zero bias was used by the non-linear error model to transfer itself to linear .At last the linear least-squares method was used to identify the tri-axial non-orthogonal error and the scale factor error. The calibration key parameters would be achieved in this way. Simulation shows that measurement error is reduced by 20 times after the accelerometer was calibrated. Therefore the calibration precision indicates that this novel method is practical in-field use.

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