Guidance of Autonomous Amphibious Vehicles for Flood Rescue Support

We develop a path-planning algorithm to guide autonomous amphibious vehicles (AAVs) for flood rescue support missions. Specifically, we develop an algorithm to control multiple AAVs to reach/rescue multiple victims (also called targets) in a flood scenario in 2D, where the flood water flows across the scene and the targets move (drifted by the flood water) along the flood stream. A target is said to be rescued if an AAV lies within a circular region of a certain radius around the target. The goal is to control the AAVs such that each target gets rescued while optimizing a certain performance objective. The algorithm design is based on the theory of partially observable Markov decision process (POMDP). In practice, POMDP problems are hard to solve exactly, so we use an approximation method called nominal belief-state optimization (NBO). We compare the performance of the NBO approach with a greedy approach

Using MTF with fixed-zoning method for automated gated imaging system in turbid medium

236-241For a typical gated system, the gated images are recorded into video format in increasing gate opening time, each frame of the video recorded is basically to “slice” the targets at different distance from camera (based on time of light). In this paper, all enhanced target images within the field of view (FOV) are fused into one 3D image. Works had been done in 1) selecting a quantitative image quality index for automated tuning system so that sectioned images with better quality can be detected accurately in turbid condition and 2) applying a fixed zoning system - sectioning method by splitting input images into 25 equal sub-images to demonstrate the concept of flexible zoning method in future works. Modulation Transfer Function (MTF) can perform better in analyzing images under turbid condition thus is selected for this application. Experiment results show that the mid-band spatial frequencies from 21 to 61 demonstrate the degradation of image quality due to the turbid water backscattering noises. Thus, we propose to use MTF in the auto-tuning system to select best quality target from multiple images. Subsequently, image fusion is performed to fuse all selected sub-images into 3D extended targets in turbid condition

Crack detection using image processing techniques for radiographic inspection of aircraft wing spar

Radiographic inspection is one of the most important non-destructive inspection methods for aircraft wing spar inspection. Traditionally, radiographic inspection is time and manpower consuming. In addition, human inspection of cracks and damage based on film radiography is very subjective, inconsistent and sometimes biased. To improve the speed and efficiency of radiographic inspection, digital X-ray systems are gaining popularity over traditional film-based X-ray. Digital radiography has emerged as a leading technology for aircraft inspection. Therefore, it is desirable to develop a computer-aided system to assist in the interpretation of digital radiographic images to increase the objectivity, accuracy and efficiency of radiographic interpretation. In this paper, a crack detection algorithm using region of interest (ROI) minimisation, thresholding and edge detection techniques is developed for radiographic inspection of an aircraft wing spar

Predictive growth model of LID: Light intensification model

General precursors and growth model of Laser Induced Damage (LID) have been the focus of research in fused silica material, such as polishing residues, fractures, and contaminations. Assuming the absorption due to trapped material and mechanical strength is the same across the surfaces, various studies have shown that the LID could be minimized by reducing the light field intensification of the layers upon the laser strikes. By revisiting the definition of non-ionising radiation damage, this paper presents the modelling work and simulation of light intensification of laser induced damage condition. Our contribution is to predict the LID growth that take into various factors, specifically on the light intensification problem. The light intensification problem is a function of the inter-layer or intra-layer micro-optical properties, such as transmittance and absorption coefficient of the material at micro- or sub-micro-meter range. The proposed model will first estimate the light propagation that convoluted with the multiply scattering light and subsequently the field intensification within the nodule dimension. This will allow us to evaluate the geometrical factor of the nodule effect over the intensification. The result show that the light intensification is higher whenever the backscattering and multiple scattering components are higher due to its interference with the incoming wave within its coherency

Modal and stress analysis of gear train design in portal axle using finite element modeling and simulation

The portal axle is a gearbox that is specially designed for off-road driving conditions. It is installed between the wheel and the axle shaft to give higher ground clearance to the vehicle. The modeling and simulation of spur gears in portal axle is important to predict the actual motion behavior. However, gear train design in portal axle is difficult to study comprehensively due to their relatively low cost and short product life cycle. In this study, modal analysis of portal axle is simulated using finite element method (FEM). Modal analysis is simulated on three different combinations of gear train system commonly designed for portal axle. The three gear trains being analyzed are gear train without idler gear, one idler gear and two idler gears. FEM static stress analysis is also simulated on three different gear trains to study the gear teeth bending stress and contact stress behavior of the gear trains in different angular positions from 0 degrees to 18 degrees. The single and double pair gear teeth contact are also considered. This methodology serves as a novel approach for gear train design evaluation, and the study of gear stress behavior in gear train which is needed in the small workshop scale industries