Reflex assisted walking for a hexapod robot

Abstract: This paper describes the performance of a hexapod robot that uses low level leg reflexes to aid in walking over uneven terrain, and is currently being developed at the University of Johannesburg. The goal of this research is a robot able to deploy in both the inspection and search and rescue roles, within an underground mine environment. The robot has six legs with three degrees of freedom per leg, and is equipped with a two degree of freedom arm with a sensor payload attached to a pan-tilt system. Throughout the development of this new robot the Design Science Research Methodology was used to guide the decision making process. This paper presents an overview of the robot, including the control architecture, and the testing conducted to verify the robot’s performance when walking over a laboratory test field

Development and early growth of fatigue cracks from corrosion damage in high strength stainless steel

AbstractThis paper investigates the influence of localised corrosion flaws caused by pitting and crevice corrosion in 15-5PH high strength stainless steel on the development and early growth of fatigue cracks. Fatigue specimens fitted with a crevice former were exposed to a 5%NaCl solution in a salt spray cabinet to produce a single flaw in the middle of the specimen and then tested in fatigue. The development and early growth of fatigue cracks were recorded using a range of techniques. After failure the shape and size of corrosion flaws where cracks initiated were measured and their largest Kt values determined by finite element analysis. Considerable variability in life response to defect Kt was found. Comparison of experimental crack growth data with fracture mechanics predictions showed evidence of a significant number of cycles occupied in transforming defects into cracks in some initiating flaws

Comparison of background subtraction techniques under sudden illumination changes

This paper investigates three background modelling techniques that have potential to be robust against sudden and gradual illumination changes for a single, stationary camera. The first makes use of a modified local binary pattern that considers both spatial texture and colour information. The second uses a combination of a frame-based Gaussianity Test and a pixel-based Shading Model to handle sudden illumination changes. The third solution is an extension of a popular kernel density estimation (KDE) technique from the temporal to spatio-temporal domain using 9-dimensional data points instead of pixel intensity values and a discrete hyperspherical kernel instead of a Gaussian kernel. A number of experiments were performed to provide a com- parison of these techniques in regard to classfication accuracy

A performance analysis of dense stereo correspondence algorithms and error reduction techniques

Abstract: Dense stereo correspondence has been intensely studied and there exists a wide variety of proposed solutions in the literature. Different datasets have been constructed to test stereo algorithms, however, their ground truth formation and scene types vary. In this paper, state-of-the-art algorithms are compared using a number of datasets captured under varied conditions, with accuracy and density metrics forming the basis of a performance evaluation. Pre- and post-processing disparity map error reduction techniques are quantified

Mean shift object tracking with occlusion handling

An object tracking algorithm using the Mean Shift framework is presented which is largely invariant to both partial and full occlusions, complex backgrounds and change in scale. Multiple features are used to gain a descriptive representation of the target object. Image moments are used to determine the scale of the target object. A kalman filter is used to successfully track the target object through partial and full occlusions, the Bhattacharyya coefficient is used to determine the measurement noise estimation

Bayesian detection of abnormal hematological values to introduce a no-start rule for heterogeneous populations of athletes.

Sports authorities exclude athletes with abnormal levels of blood parameters. Here, the consideration of longitudinal blood profiles together with heterogeneous factors such as ethnicity and age produces a model with enhanced sensitivity to detect blood doping. Sports disciplines with heterogeneous populations now have a general method to introduce the no-start rule

Robust single image noise estimation from approximate local statistics

Abstract: Abstract—A novel method for estimating the variance and standard deviation of the additive white Gaussian noise contained in an image will be presented. Only a single image is used to estimate the noise properties. Local image outliers are discarded, this allows us to separate the additive zero mean white Gaussian noise contained in a noisy image from the original image structure..

Sheep scab in Northern Ireland: its distribution, costs and farmer knowledge about prevention and control

Sheep scab (psoroptic mange), which is endemic in the United Kingdom (UK) flock, has a significant, negative impact on sheep welfare. Nothing has previously been published about the distribution of sheep scab in Northern Ireland (NI), nor about Northern Irish farmers’ knowledge and behaviours relating to the disease, its treatment, prevention and control. Between March and June 2021 an online questionnaire on the disease was completed by sheep farmers in NI. Forty-four respondents out of a total of 122 valid returns (36%) indicated that they had at least one outbreak of sheep scab in their flock within the previous five years. These flocks were spread throughout NI and included flocks grazing on common land. Farmers reporting sheep scab in their flock considered movements of sheep between flocks to be the main cause of flock infestation. Respondents demonstrated knowledge gaps in relation to the parasite biology, disease transmission, prevention and treatment options, as well as a lack of awareness of some of the relevant industry guidelines. We highlight that some farmers rely on clinical signs alone to rule out the possibility that newly purchased sheep are infested with sheep scab before mixing them with their flock. This activity poses a high risk for the introduction of sheep scab into previously uninfested flocks. The inadequacy of some farmers’ quarantine rules, or their inability to follow them, was also reported by farmers as being the cause of their flock infestation. Sheep scab outbreaks were shown to result in significant financial cost, with some farmers reporting their most recent outbreak had cost over £2500 ($3329). The paper also highlights that in addition to the animal health and welfare impact and financial cost, sheep scab was reported to have a social cost: 94 respondents (79%) agreed that a sheep scab outbreak caused emotional stress to affected farmers. These findings have provided evidence of the widespread nature of sheep scab in the NI flock, and of the knowledge gaps and behaviours which need to be addressed to improve sheep scab control. This will require a combination of focused research, knowledge exchange between farmers, advisors, policy makers and regulators, and co-developed disease control plans at a flock and national level