支持向量机理论的研究与进展

回顾了支持向量机理论的发展历程,介绍了支持向量机的标准训练算法及其分解算法、变形算法、几何算法以及多类分类算法,重点描述了最小二乘支持向量机算法,总结了支持向量机理论及其应用的现状与存在问题,对支持向量机的未来发展方向进行了展望。     

The adaptive Gaussian mixtures unscented Kalman filter for attitude determination using light curves

The Adaptive Gaussian Mixtures Unscented Kalman Filter (AGMUKF) is introduced to estimate the attitude of a Resident Space Object using light curves. This filter models the state probability density function as a Gaussian Mixture. This enables to capture the non-linearities of the light-curve measurement model. A non-linearity index is used to refine the mixture when necessary, and individual Gaussian kernels are merged back together when their relative distance is below a certain threshold. A conventional attitude Unscented Kalman Filter (UKF) is used to propagate and update each kernel. The AGMUKF efficiently maintains the mixture population as low as possible, while still being able to represent non-symmetric, multimodal, arbitrarily complex distributions. Therefore, it is presented as a promising alternative to Particle-Filter-based implementations, the current state of the art used in sequential attitude estimation from light curves. The non-linearity index has been used to show that the measurement model is the main contributor to the system non-linearity. Results have demonstrated the superiority of the AGMUKF w.r.t. the UKF for attitude determination, and that it can converge for high initial state uncertainty cases, successfully capturing the non-Gaussian probability distribution of the state.     

润滑油红外光谱去噪预处理方法

采用小波包变换软阈值去噪方法对润滑油的红外光谱进行去噪预处理,结合偏最小二乘法进行定量预测,并与常用的平滑去噪方法进行对比。结果表明,小波包变换能有效地去除红外光谱的噪声,以此为基础建立的润滑油酸值模型的预测精度高于常用的平均平滑法和 Savitzky-Golay卷积平滑法这 2种平滑去噪方法的预测精度。     

一种基于试验数据的发动机特性曲线拟合

准确的发动机特性曲线是其性能计算的基础。文章讨论了多种情况的特性曲线插值方法:在工作点位置区间内,对小数据情况引入了新的插值方法；多数据时,采用三次样条插值方法进行插值；在工作点位置区间外,数据较多时,基于最小二乘法进行不同工作点的拟合；当工作点位置数据较少,利用新的插值方法在区间内引入虚拟工作点增加数据点,后按照数据较多的情况处理。所得结果与实际数值比较,精度较高,具有一定的参考价值。     

未知纬度条件下基于空间圆拟合的SINS初始对准方法

传统的捷联惯导系统(SINS)晃动基座初始对准算法,如积分双矢量方法和多矢量Wahba方法等均需要精确的纬度信息,粗对准偏航角误差较大.针对此特点,提出了一种未知纬度条件下基于空间圆拟合的SINS初始对准方法.根据重力矢量在惯性系中绕地轴旋转包含北向信息的特征,以初始时刻凝固载体坐标系作为惯性系,首先对重力矢量在凝固载体系内进行投影并滤波,对其矢量端点进行空间圆拟合,然后通过三角几何关系得到导航坐标系,从而完成对准过程.通过仿真验证,证实了该对准方法不需要已知对准点的精确位置信息,相比于积分双矢量方法与多矢量Wahba方法,偏航角对准精度分别提高了12.37'与5.10'.