Topologic Maps for Robotic Exploration of Underground Flooded Mines

The mapping of confined environments in mobile robotics is traditionally tackled in dense occupancy maps, requiring large amounts of storage. For some use cases, such as the exploration of flooded mines, the use of dense maps in processing slow down processes like path generation. I introduce a method of generating topological maps in constrained spaces such as mines. By taking a structure with fewer points, traversal and storage of explored space can be made more efficient, avoiding com plex graphs generated by methods like RRT and it’s variants. It’s simpler structure also allows for more intuitive human-machine interactions with it’s fewer points. I also introduce an autonomous frontier-based exploration approach to generate the topological map during exploration, taking advantage of it’s traversal to navigate through known space. With this work, simulation tests show it is possible to success fully extract a simpler graph structure describing the topology during autonomous exploration and that this structure is robust through explored regionsO mapeamento de ambientes confinados em robótica móvel, é tradicionalmente abordado em mapas densos de ocupação, necessitando de grandes quantidades de armazenamento. Para certos casos, tal como a exploração de minas submersas, o uso de mapas densos no processamento, atrasa processos como geração de caminhos. Utilizando uma estrutura com menos pontos, a travessia e o armazenamento de espaço explorado tornam-se mais eficientes, evitando grafos complexos gerados por métodos como RRT e variantes. A sua estrutura mais simples permite também interações homem-máquina com o seu número reduzido de pontos. Introduzo também uma abordagem autónoma de exploração baseada em fronteiras, para gerar o mapa topo lógico durante a exploração, tirando vantagem da travessia do mesmo para navegar por espaço conhecido. Com este trabalho, testes em simulação mostram ser possível extrair uma estrutura sob forma de grafo, descrevendo a topologia ao longo de explorações autónomas e que esta estrutura é robusta para a travessia em regiões explorada

Automating the Reconstruction of Neuron Morphological Models: the Rivulet Algorithm Suite

The automatic reconstruction of single neuron cells is essential to enable large-scale data-driven investigations in computational neuroscience. The problem remains an open challenge due to various imaging artefacts that are caused by the fundamental limits of light microscopic imaging. Few previous methods were able to generate satisfactory neuron reconstruction models automatically without human intervention. The manual tracing of neuron models is labour heavy and time-consuming, making the collection of large-scale neuron morphology database one of the major bottlenecks in morphological neuroscience. This thesis presents a suite of algorithms that are developed to target the challenge of automatically reconstructing neuron morphological models with minimum human intervention. We first propose the Rivulet algorithm that iteratively backtracks the neuron fibres from the termini points back to the soma centre. By refining many details of the Rivulet algorithm, we later propose the Rivulet2 algorithm which not only eliminates a few hyper-parameters but also improves the robustness against noisy images. A soma surface reconstruction method was also proposed to make the neuron models biologically plausible around the soma body. The tracing algorithms, including Rivulet and Rivulet2, normally need one or more hyper-parameters for segmenting the neuron body out of the noisy background. To make this pipeline fully automatic, we propose to use 2.5D neural network to train a model to enhance the curvilinear structures of the neuron fibres. The trained neural networks can quickly highlight the fibres of interests and suppress the noise points in the background for the neuron tracing algorithms. We evaluated the proposed methods in the data released by both the DIADEM and the BigNeuron challenge. The experimental results show that our proposed tracing algorithms achieve the state-of-the-art results

Simulation tests for the operation of a water main with break pressure tanks.

Master of Science in Chemical Engineering. University of KwaZulu-Natal, Durban 2016.The Ashley Drive break pressure tank (BPT-20 ℓ) has been installed on Durban’s Western Aqueduct. Its purpose is to release the 20 bar gravity head of the 1.4m trunk main supply from Umgeni Water at Umlaas Road. The expected peak conditions (400 ℓ/) will only allow 14 minutes for valves to close, yet they must be moved slowly in order to avoid dynamic shock. The high pressure upstream supply is admitted to the BPT through a set of thee parallel sleeve valves, which are in a control loop to maintain level in the BPT against the downstream draw. These cavitation-resistant valves cannot be operated without electrical power, so an added complication of the design is a set of 3 hydraulically-operated globe valves which switch in at extreme tank levels. Though the commissioning of the Ashley Drive BPT is already in progress, it is important to simulate the overall operation of the system for projected future flows, in order to detect possible operational problems, and to build in solutions if necessary. Optimisations include such issues as the valve closing sequence and speeds, settling level variations, and smoothness of the draw from Umgeni Water. The simulation study involved the modelling of the trunk main, the Ashley Drive BPT, the downstream Wyebank BPT and the reservoirs drawing from the trunk main before and after these two BPTs. Data handling techniques were developed in order to formulate the daily demand profiles for each of the reservoirs. Design information was used to calculate the hydraulic parameters that featured in the simulation, and to determine the residual pressures at the inlet valve sets of the BPTs. Implicit calculations with the Newton-Raphson iterative method were employed in order to obtain a pressure distribution across the BPT valves. Simple mechanisms were built into the MATLAB® program in order to accommodate the complexities of the system, e.g. the possibility of power loss, valve or BPT chamber maintenance, or the deliberately slowed movement of the valves to avoid pressure surges within the pipeline. The analysis of the results of the simulation study involved examining the efficacy of the control set-points and valve sequencing, and determining whether these settings satisfy the design specifications. Random and anticipated scenario testing was carried out within the study in order to accommodate for situations such as electricity outages or unusual consumer demands. The BPT control system was analysed to assess its adequacy and the risks associated with the proposed staggered sleeve valve control scheme. The results of this investigation are presented as multiple time-sequence graphs depicting the results of the different scenario tests. Support for the design concept, additional recommendations and indications of adverse scenarios, have emerged from this study. The original design is found to be capable of duty within the ranges of expected normal operation in 2036, and the system was observed to be capable of conveying a throughput greater than that of the design. The normal operating level was also found to be higher than intended, and valve oscillations were deemed a significant concern. It was established that operation with just two sleeve valves active within each BPT would achieve better correspondence to the design specifications. The revised control system (Control 2.0) was found to be better suited to the application, but was also diagnosed to be too slow to react under certain circumstances