基于合作目标的三维空间贝叶斯传感器配准算法

当存在合作目标时,基于合作目标的传感器配准算法往往优于基于多站测量的传感器配准算法.传统的基于合作目标的传感器配准算法将系统误差看作是一个确定未知量,对未知量的估计采用了非贝叶斯的参数估计算法,如极大似然法、最小二乘法等.当传感器量测噪声相对于传感器系统误差不可忽略时,上述算法估计效果较差.在此背景下,提出了基于合作目标的贝叶斯传感器配准算法,通过将传感器系统误差建模成未知的随机过程,并通过卡尔曼滤波消除量测噪声对系统误差估计带来的影响,实验结果表明,方法具有较好的实用性.     

基于修正罗德里格参数的小卫星SSUKF姿态确定

用无陀螺的三轴稳定偏置动量小卫星三轴磁强计和太阳敏感器获得观测矢量,提出了一种基于超球面分布采样Unscented变换滤波(SSUKF)和修正罗德里格参数(MRPs)的姿态估计方法,给出了算法模型.SSUKF在保证滤波性能的基础上减少了采样点个数,减轻了星载计算机的负载;用MRPs描述小卫星姿态大幅减少了计算量.某小卫星的仿真结果表明:算法兼顾了精度、收敛速度和鲁棒性,且提高了计算效率,适于小卫星.     

过滤式阴极电弧沉积类金刚石薄膜工艺研究

研究了过滤式阴极电弧沉积系统的稳弧工艺参数,通过正交试验获得最佳稳弧参数。并且研究了弯管内置挡板对宏观粒子过滤效果的影响。采用喇曼光谱研究了偏压对生成的类金刚石薄膜性能的影响,证明－１００Ｖ偏压下获得的类金刚石薄膜有最佳的ＳＰ３含量。扫描电镜测试表明,在（１１１）硅基片上获得致密的膜,但在高速钢基体上沉膜堆积现象比较严重,不易获得优质类金刚石膜。同时也给出了类金刚石的原子力显微照片（ＡＦＭ）,表明稳弧参数对类金刚石薄膜表面形貌有较大的影响。     

元强化学习综述

元强化学习是指自动从一组相关任务中学习强化学习所需归纳偏置的相关理论和方法,对于提高强化学习算法在困难场景下的样本效率和泛化能力具有重要用途。本文提出一种新的元强化学习框架,指出设计和分析一个元强化学习算法需要同时考虑学习经验（相关任务）、归纳偏置及学习目标3个独立因素及这3个因素之间的依赖关系。在此基础上对该领域的研究现状进行了分析和总结,特别对近年来元强化学习若干文献进行了分析和归类,并详细阐述了几种代表性算法的原理及各自特点。本文还对元强化学习常用的实验环境和性能评价方法进行了介绍,对该领域的不足和未来的发展方向进行了讨论和分析。     

极端低温下电液伺服阀温漂特性分析

针对电液伺服阀在极端低温下温漂大的问题，以＋40℃时电液伺服阀初始零偏为基准，采用线性回归方法分析了某型射流管伺服阀不同温度的零偏试验数据，得到了极端低温下的伺服阀温漂与＋40℃时初始零偏的数学关系。分析与试验结果表明：极端低温时射流管伺服阀的温漂与＋40℃时的初始零偏存在非常显著的线性关系。温漂与电液伺服阀制造与装配工艺过程密切相关，与结构及其装配不对称有关。电液伺服阀结构上的微观不对称现象，在极端低温下显现出来，尤其是呈现出较大的温漂。降低温漂的主要措施是提高电液伺服阀结构与装配的对称性，降低初始零偏。     

Comparison of convergence time and positioning accuracy among BDS,GPS and BDS/GPS precise point positioning with ambiguity resolution

Precise point positioning (PPP) usually takes about 30?min to obtain centimetre-level accuracy, which greatly limits its application. To address the drawbacks of convergence speed and positioning accuracy, we develop a PPP model with integrated GPS and BDS observations. Based on the method, stations with global coverage are selected to estimate the fractional cycle bias (FCB) of GPS and BDS. The short-term and long-term time series of wide-lane (WL) FCB, and the single day change of narrow-lane (NL) FCB are analysed. It is found that the range of GPS and BDS non-GEO (IGSO and MEO) WL FCB is stable at up to a 30-day-time frame. At times frame of up to 60?days, the stability is reduced a lot. Whether for short-term or long-term, the changes in the BDS GEO WL FCB are large. Moreover, BDS FCB sometimes undergoes a sudden jump. Besides, 17 and 10 stations were used respectively to investigate the convergence speed and positioning errors with six strategies: BDS ambiguity-float PPP (Bfloat), GPS ambiguity-float PPP (Gfloat), BDS/GPS ambiguity-float PPP (BGfloat), BDS ambiguity-fixed PPP (Bfix), GPS ambiguity-fixed (Gfix), and BDS/GPS ambiguity-fixed (BGfix). The average convergence speed of the ambiguity-fixed solution is greatly improved compared with the ambiguity-float solution. In terms of the average convergence time, the Bfloat is the longest and the BGfix is the shortest among these six strategies. Whether for ambiguity-float PPP or ambiguity-fixed PPP, the convergence reduction time in three directions for the combined system is the largest compared with the single BDS. The average RMS value of the Bfix in three directions (easting (E), northing (N), and up (U)) are 2.0?cm, 1.5?cm, and 5.9?cm respectively, while those of the Gfix are 0.8?cm, 0.5?cm, and 1.7?cm. Compared with single system, the BDS/GPS combined ambiguity-fixed system (BGfix) has the fastest convergence speed and the highest accuracy, with average RMS as 0.7?cm, 0.5?cm, and 1.9?cm for the E, N, U components, respectively.     

用于微小卫星的陀螺随机常值偏置误差的在轨标定

结合陀螺在微小卫星上的使用,提出了一种不依赖于其余敏感器信息的陀螺随机常值偏置实时在轨标定技术.该技术利用陀螺在轨实时测量信息,结合卫星姿态动力学本身的约束,实现了陀螺加电后初始随机零偏的在轨实时确定.分析了标定模型的可观性,得出了该技术的适用条件.仿真结果表明,该标定算法具有较高精度,对陀螺采样频率具有一定的鲁棒性,并具有较快的收敛速度,在给定的姿态动力学模型的精度条件下,100 s内基本稳定,收敛精度在1.0 (°)/h左右,标定性能可满足空间任务的需求.     

一种月面采样量的在轨自主测量方法

月面采样量的在轨自主测量是实现月面自主采样的必要环节。本文设计了一种月面采样装置，根据图像信息实现对月面采样量的在轨自主测量。针对图像中目标与背景灰度差较小、背景区域噪声较多的特点，采用了改进型最大类间方差法与连通标记自适应去噪方法，实现了采样区域较为准确的分割。针对单目相机无法直接获取采样区域尺寸的特点，利用已知物体尺寸进行在轨自主标定，结合图像中提取出的采样区域，完成了采样区域尺寸的计算，实现了采样量的在轨自主测量。试验结果表明，在轨自主测量结果与实际结果吻合，本文提出的在轨自主测量方法有效。     

Provocative radio transients and base rate bias: A Bayesian argument for conservatism

Most searches for alien radio transmissions have focused on finding omni-directional or purposefully earth-directed beams of enduring duration. However, most of the interesting signals so far detected have been transient and non-repeatable in nature. These signals could very well be the first data points in an ever-growing data base of such signals used to construct a probabilistic argument for the existence of extraterrestrial intelligence. This paper looks at the effect base rate bias could have on deciding which signals to include in such an archive based upon the likely assumption that our ability to discern natural from artificial signals will be less than perfect.     

高精度激光陀螺仪温度补偿模型研究

在实际工程中,高精度激光陀螺仪的输出零偏会随着温度变化发生漂移,限制了其应用。为了降低和补偿温度对陀螺零偏的影响,提高陀螺应用性能,降低装备成本,从探究温度对输出零偏的影响因素出发,建立了一种考虑多影响因素的温度补偿模型,并设计了相应的温度试验。试验结果表明,高精度机抖激光陀螺的零偏和温度、温变速率、温度梯度具有较好的相关性和重复性,该温度补偿模型补偿效果显著,可基本消除零偏随温度变化的趋势,有效降低武器装备对零部件的要求,能够降低应用成本,具有很强的实用价值。