室内自校准导航定位方法

提出一种室内信号强度路径损耗自校准模型,与传统的因墙壁等障碍物引起的信号强度路径损耗模型相比,该自校准模型既不需要大量试验,而且精度还更高。在此基础上,推导出距离量测方程的协方差矩阵,建立一种基于RSSI的室内高精度定位方法。同时,提出一种新的步长估计模型和行人航位自校准推算方法,该模型通过综合利用X轴与Y轴加速度极差的平方和进行步长估计,与通过Z轴加速度极差估计步长的Weinberg模型相比,它不但克服了因地面不平(如上下坡或上下楼等)导致的步长误差,而且在平地上也具有更高的精度。并建立一种基于RSSI的室内自校准导航方法,能够通过自校准滤波对步长参数K进行实时估计,解决了传统方法需通过大量训练来确定参数K的问题,显著提高导航精度。

Reducing Item Exposure in Computerized Adaptive Testing Systems Using Automatic Item Generation

This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during examinees prior testing. Disadvantage of the mentioned item calibration method is the item exposure; when test items become familiar to the examinees. To reduce the item exposure, automatic item generation method is used, where item models are being constructed based on already calibrated test items without losing already estimated item parameters. A technic of item model extraction method from the already calibrated and therefore exposed test items described, which can be used by the test item development specialists to integrate automatic item generation principles with the existing testing applications.

基于最小二乘法的自校准位姿方案

基于辅助测量装置中栅格板的不同位姿,构建了有关工作台误差和栅格板误差的数学模型。根据最小二乘原理将误差方程转化为正规方程。通过研究位姿方案对关系矩阵的秩的影响,归纳总结了位姿与自校准模型之间的规律。依据方程具备最小二乘解的条件,自校准过程中栅格板必须在初始位姿的基础上经过旋转90°及平移的位姿变换,并进行了仿真。研究结果表明,只有包含三种基本位姿的位姿方案才能使仿真计算值接近真实值,此基本三位姿是实现最小二乘法自校准的充分必要条件。