幅相误差对射频仿真系统目标位置精度的影响

依据电磁场理论，直接从三元组出发推导了射频仿真系统目标视在角位置方程。用数字仿真的手段，在整个阵面上随机均匀取点并模拟实际系统所产生的幅相误差，得出了几种情况下目标位置误差的统计分布，给出了它们的均值和方差。     

人工神经网络D最优设计的一种方法

利用初始的少数实例求初步的权值矩阵，根据该矩阵的人工神经网络模型找出偏导数向量的模最大时对应的设计矩阵，又根据该设计矩阵的实例求出新的权值矩阵，寻找新一轮设计矩阵。通过用泰勒级数展开的神经网络输出公式，求该输出函数的方差，证明了偏导数的向量的模最大是相关矩阵行列式最小(D最优)的充分条件。     

基于RBF的机械手建模误差补偿自适应控制

针对机械手动力学建模误差,提出了基于RBF神经网络误差补偿的自适应控制策略。在基于逆动力学的计算力矩控制方法的基础上,对系统输入与目标轨迹进行修正,设计了两种误差补偿自适应控制器。利用RBF神经网络对修正项在线自学习,并根据Lyapunov稳定性理论建立了网络权重自适应学习律,保证了跟踪误差的收敛及系统的稳定。以平面转动双臂机械手轨迹跟踪为例进行仿真,结果表明该方法能够有效地补偿建模误差,提高了系统的控制性能并使控制系统具有对参数摄动的鲁棒性,对于机械手自适应控制具有一定的可行性。     

Mobile channel estimation for MU-MIMO systems using KL expansion based extrapolation

In multi-user multiple input multiple output(MU-MIMO) systems,the outdated channel state information at the transmitter caused by channel time variation has been shown to greatly reduce the achievable ergodic sum capacity.A simple yet effective solution to this problem is presented by designing a channel extrapolator relying on Karhunen-Loeve(KL) expansion of timevarying channels.In this scheme,channel estimation is done at the base station(BS) rather than at the user terminal(UT),which thereby dispenses the channel parameters feedback from the UT to the BS.Moreover,the inherent channel correlation and the parsimonious parameterization properties of the KL expansion are respectively exploited to reduce the channel mismatch error and the computational complexity.Simulations show that the presented scheme outperforms conventional schemes in terms of both channel estimation mean square error(MSE) and ergodic capacity.     

Improved adaptive pruning algorithm for least squares support vector regression

As the solutions of the least squares support vector regression machine(LS-SVRM) are not sparse,it leads to slow prediction speed and limits its applications.The defects of the existing adaptive pruning algorithm for LS-SVRM are that the training speed is slow,and the generalization performance is not satisfactory,especially for large scale problems.Hence an improved algorithm is proposed.In order to accelerate the training speed,the pruned data point and fast leave-one-out error are employed to validate the temporary model obtained after decremental learning.The novel objective function in the termination condition which involves the whole constraints generated by all training data points and three pruning strategies are employed to improve the generalization performance.The effectiveness of the proposed algorithm is tested on six benchmark datasets.The sparse LS-SVRM model has a faster training speed and better generalization performance.     

Novel reference range selection method in InlSAR imaging

Aiming at the reference range selection for different antennas in interferometric inverse synthetic aperture radar (InISAR) systems, this paper proposes a respective focusing (RF) method. The reference ranges for echoes of different antennas are selected respectively for RF, which is different from the traditional uniform focusing (UF) with the same reference range applied to all the antennas. First, a comparison between UF and RF for InISAR signal model considering the ranging error is given. Compared with RF, UF has an advantage in overcoming the ranging error differences between different antennas. Then the influence of ranging error upon the interferometric imaging with RF is investigated particularly, and it is found that the ranging error differences between different antennas are far smaller than the wavelength, which is advantageous to imaging. By comparing the capabilities of interferometric imaging between RF and UF, it is concluded that RF is a better choice in conquering problems such as image mismatching and phase ambiguity even with ranging errors. Simulations demonstrate the validity of the proposed method.     

非均匀圆阵天线模型解模糊误差研究

基于干涉仪的立体基线法与传统测向解模糊方法相比,天线摆放方式更为灵活。针对这一优点,建立了非均匀圆阵天线阵列模型,给出了该模型理论测向误差的表达式。通过分析解算过程中影响测向误差的因素,提出了一种减小天线阵列实际测向误差的方法。为保证系统具有一定的解模糊能力,给出了该方法中天线孔径对系统解模糊频段的限制条件。基于建立的天线模型,通过Matlab仿真,验证了方法及理论分析的正确性,对合理选择天线盘孔径、减小测向系统的误差具有可行性。     

挠性捷联惯组的多位置对准技术

弹用惯组的误差是影响系统落点导航精度的关键因素。针对如何利用已知的航向信息最大程度地提高弹用挠性陀螺的实际使用精度的问题,将多位置对准技术应用于惯组误差的在线标定,利用行列式法对陀螺静态漂移误差进行了可观性分析,给出常用两位置对准的理论分析及最优三位置的限定方程。仿真结果表明,最优三位置对准可以有效分离常值漂移和与比力一次项有关的漂移,实现挠性陀螺静态漂移误差状态变量全部可观测,最大程度地降低其对系统误差的影响。     

改进的X波段雷达测海表面流算法

为了克服传统X波段雷达测表面流算法存在低流速时误差较大和测量结果不稳定的缺点,提出了一种改进的算法。首先使用色散关系带通滤波器滤除海杂波图像谱中非海浪信号;然后使用调制传递函数对剩余海浪图像谱进行非线性校正,得到真实海浪谱;下一步根据结构风险最小化原则,确定支持向量机中海浪谱分量隶属度;最后使用真实海浪谱和隶属度函数的乘积加权最小二乘法进行初始估流和迭代估流。根据实测岸基X雷达数据实验,结果表明改进算法弥补了传统算法中存在的上述缺点,具有较高的测量精度、稳定性和很好的应用价值。     

动力学模型系统误差及其协方差阵的随机加权拟合法

在现有的基于移动窗口函数模型和随机模型系统误差自适应拟合方法的基础上,提出一种基于移动窗口动态导航模型系统误差的随机加权拟合法,在相同的窗口内给出了相应的状态预报向量协方差阵的随机加权拟合。由于动力学模型系统误差难以直接修正,采用修正状态估计误差向量及动力学模型误差向量的方法,实现对动力学模型系统误差的修正,然后利用修正后的动力学模型及相应的协方差阵进行导航滤波计算,有效地抑制动力学模型系统系统误差的影响,提高导航解算的精度。仿真结果证明,采用随机加权拟合后的算法精度优于未进行拟合的卡尔曼滤波和自适应卡尔曼滤波算法。