针对矿井巷道环境内存在大量的设备和设施,会造成电磁波传播的NLOS(non line of sight)时延、对矿井TOA(time of arrival)定位精度产生不利影响,根据成因将巷道电磁波传播NLOS时延分为随机NLOS时延和固定NLOS时延,分析了两类NLOS时延造...针对矿井巷道环境内存在大量的设备和设施,会造成电磁波传播的NLOS(non line of sight)时延、对矿井TOA(time of arrival)定位精度产生不利影响,根据成因将巷道电磁波传播NLOS时延分为随机NLOS时延和固定NLOS时延,分析了两类NLOS时延造成测距误差的特点。为了分步抑制两类NLOS时延造成的TOA测距定位误差,提出基于改进均值滤波和参数拟合的矿井TOA几何定位算法。针对巷道随机NLOS时延造成的以脉冲形式存在的TOA测距误差,提出基于偏差值丢弃的加权均值滤波算法加以抑制;进而提出依据定位区域巷道固定NLOS时延参数拟合方法,用以抑制其造成的TOA测距正向偏移误差,最后采用几何方法进行目标位置的估计。实验结果表明,提出的方法对巷道NLOS时延造成的TOA定位误差具有显著的抑制作用,能够保证矿井TOA定位的精度。展开更多
A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure an...A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics.A nonplanar vortex lattice method is used to compute the nonplanar aerodynamics.The nonlinear finite element method is introduced to consider the structural geometric nonlinearity.Moreover,the surface spline method is used for structure/aerodynamics coupling.Finally,by combining the equilibrium equations of rigid motions of the deformed aircraft,the nonlinear trim problem of the flexible aircraft is solved by iterative method.For instance,the longitudinal trim analysis of a flexible aircraft with large-aspect-ratio wings is carried out by both the nonlinear method presented and the linear method of MSC Flightloads.Results obtained by these two methods are compared,and it is indicated that the results agree with each other when the deformation is small.However,because the linear method of static aeroelastic analysis does not consider the nonplanar aerodynamic effects or structural geometric nonlinearity,it is not applicable as the deformations increase.Whereas the nonlinear method presented could solve the trim problem accurately,even the deformations are large,which makes the nonlinear method suitable for rapid and efficient analysis in engineering practice.It could be used not only in the preliminary stage but also in the detail stage of aircraft design.展开更多
文摘针对矿井巷道环境内存在大量的设备和设施,会造成电磁波传播的NLOS(non line of sight)时延、对矿井TOA(time of arrival)定位精度产生不利影响,根据成因将巷道电磁波传播NLOS时延分为随机NLOS时延和固定NLOS时延,分析了两类NLOS时延造成测距误差的特点。为了分步抑制两类NLOS时延造成的TOA测距定位误差,提出基于改进均值滤波和参数拟合的矿井TOA几何定位算法。针对巷道随机NLOS时延造成的以脉冲形式存在的TOA测距误差,提出基于偏差值丢弃的加权均值滤波算法加以抑制;进而提出依据定位区域巷道固定NLOS时延参数拟合方法,用以抑制其造成的TOA测距正向偏移误差,最后采用几何方法进行目标位置的估计。实验结果表明,提出的方法对巷道NLOS时延造成的TOA定位误差具有显著的抑制作用,能够保证矿井TOA定位的精度。
基金supported by the National Natural Science Foundation of China (Grant Nos. 11172025,91116005)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20091102110015)
文摘A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics.A nonplanar vortex lattice method is used to compute the nonplanar aerodynamics.The nonlinear finite element method is introduced to consider the structural geometric nonlinearity.Moreover,the surface spline method is used for structure/aerodynamics coupling.Finally,by combining the equilibrium equations of rigid motions of the deformed aircraft,the nonlinear trim problem of the flexible aircraft is solved by iterative method.For instance,the longitudinal trim analysis of a flexible aircraft with large-aspect-ratio wings is carried out by both the nonlinear method presented and the linear method of MSC Flightloads.Results obtained by these two methods are compared,and it is indicated that the results agree with each other when the deformation is small.However,because the linear method of static aeroelastic analysis does not consider the nonplanar aerodynamic effects or structural geometric nonlinearity,it is not applicable as the deformations increase.Whereas the nonlinear method presented could solve the trim problem accurately,even the deformations are large,which makes the nonlinear method suitable for rapid and efficient analysis in engineering practice.It could be used not only in the preliminary stage but also in the detail stage of aircraft design.
