Planar-Based Visual Inertial Navigation: Observability Analysis and Motion Estimation

In this paper, we address the problem of ego-motion estimation by fusing visual and inertial information. The hardware consists of an inertial measurement unit (IMU) and a monocular camera. The camera provides visual observations in the form of features on a horizontal plane. Exploiting the geometric constraint of features on the plane into visual and inertial data, we propose a novel closed form measurement model for this system. Our first contribution in this paper is an observability analysis of the proposed planar-based visual inertial navigation system (VINS). In particular, we prove that the system has only three unobservable states corresponding to global translations parallel to the plane, and rotation around the gravity vector. Hence, compared to general VINS, an advantage of using features on the horizontal plane is that the vertical translation along the normal of the plane becomes observable. As the second contribution, we present a state-space formulation for the pose estimation in the analyzed system and solve it via a modified unscented Kalman filter (UKF). Finally, the findings of the theoretical analysis and 6-DoF motion estimation are validated by simulations as well as using experimental data.     

The sulphidation of alloys used in a fluidized bed combustor

The results of an investigation of the sulphidation behaviour of lncoloy BOOH and AISI 310 stainless steel in coal combustion conditions at temperatures between 650°C and 900°C are presented. Laboratory tests were carried out in controlled environments in the presence of solids representative of fluidized bed combustor operation. The morphology and composition of scale formed during sulphidation was examined and compared with that from tube samples removed from test rigs operated by the National Coal Board. The results have shown that at 900°C a gas mixture corresponding to the equilibrium conditions close to the coexistence point for CaS0₄, CaO and CaS on the phase stability diagram is sufficient to induce sulphidation. However, at lower temperatures an interaction between the deposit and the protective oxide is necessary and in some cases the presence of typical contaminants found in coals is an added requirement. The morphology of the corrosion products found in practice can be reproduced under controlled conditions in laboratory tests. The results are interpreted in terms of likely mechanisms of the processes involved.     

Shock loading of 3D woven composites: A validated finite element investigation

In a companion paper in this issue (Pankow et al., 2010 [1]), experimental results for the deformation response of 3D glass fiber textile composites subjected to shock wave pulse pressure loading were presented. In this paper, finite element models are developed to simulate the deformation response and damage development observed in the experiments. Two levels of models are presented, with the first focused on a layered, homogenous orthotropic model that examined the bulk macroscopic deformation response. In the second model, each layer is represented to capture the interactions between fiber tows and matrix, taking into account the discrete non-homogeneous material distribution in each layer. Both models incorporated a user defined subroutine within the commercial software ABAQUS to capture matrix micro-cracking, which is responsible for damage development and growth. Results from the computational models correlated well with experimental results and observed locations of matrix micro-cracking.     

英国火狐

正"7月的一个晚上大概7:45左右,我在Surrey的英国野生动物中心拍摄了这张照片。这是我当天第二次前往狐狸饲养圈,为了在黄昏的时候再拍摄一次。较早之前刚下完一场雨,植物叶子的颜色因此显得异常鲜艳。我一直觉得画面中的橙色和绿色搭配在一起显得十分美妙。浅景深的控制是刻意的,目的是把狐狸从背景中分离出来,如你所见,把狐狸犀利的眼神突显出来是十分必要的。"     

孩子的天然学堂

在澳大利亚,伴随着妇女就业和单亲家庭的增长,多数家庭和儿童都非常依赖于儿童看护服务,比如,社区幼儿园、幼儿中心、临时家